linux_dsm_epyc7002/arch/x86/kernel/tsc_sync.c

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/*
* check TSC synchronization.
*
* Copyright (C) 2006, Red Hat, Inc., Ingo Molnar
*
* We check whether all boot CPUs have their TSC's synchronized,
* print a warning if not and turn off the TSC clock-source.
*
* The warp-check is point-to-point between two CPUs, the CPU
* initiating the bootup is the 'source CPU', the freshly booting
* CPU is the 'target CPU'.
*
* Only two CPUs may participate - they can enter in any order.
* ( The serial nature of the boot logic and the CPU hotplug lock
* protects against more than 2 CPUs entering this code. )
*/
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
#include <linux/topology.h>
#include <linux/spinlock.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/nmi.h>
#include <asm/tsc.h>
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
struct tsc_adjust {
s64 bootval;
s64 adjusted;
unsigned long nextcheck;
bool warned;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
};
static DEFINE_PER_CPU(struct tsc_adjust, tsc_adjust);
void tsc_verify_tsc_adjust(bool resume)
{
struct tsc_adjust *adj = this_cpu_ptr(&tsc_adjust);
s64 curval;
if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST))
return;
/* Rate limit the MSR check */
if (!resume && time_before(jiffies, adj->nextcheck))
return;
adj->nextcheck = jiffies + HZ;
rdmsrl(MSR_IA32_TSC_ADJUST, curval);
if (adj->adjusted == curval)
return;
/* Restore the original value */
wrmsrl(MSR_IA32_TSC_ADJUST, adj->adjusted);
if (!adj->warned || resume) {
pr_warn(FW_BUG "TSC ADJUST differs: CPU%u %lld --> %lld. Restoring\n",
smp_processor_id(), adj->adjusted, curval);
adj->warned = true;
}
}
x86/tsc: Force TSC_ADJUST register to value >= zero Roland reported that his DELL T5810 sports a value add BIOS which completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with random negative TSC_ADJUST values, different on all CPUs. That renders the TSC useless because the sycnchronization check fails. Roland tested the new TSC_ADJUST mechanism. While it manages to readjust the TSCs he needs to disable the TSC deadline timer, otherwise the machine just stops booting. Deeper investigation unearthed that the TSC deadline timer is sensitive to the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an interrupt storm caused by the TSC deadline timer. This does not make any sense and it's hard to imagine what kind of hardware wreckage is behind that misfeature, but it's reliably reproducible on other systems which have TSC_ADJUST and TSC deadline timer. While it would be understandable that a big enough negative value which moves the resulting TSC readout into the negative space could have the described effect, this happens even with a adjust value of -1, which keeps the TSC readout definitely in the positive space. The compare register for the TSC deadline timer is set to a positive value larger than the TSC, but despite not having reached the deadline the interrupt is raised immediately. If this happens on the boot CPU, then the machine dies silently because this setup happens before the NMI watchdog is armed. Further experiments showed that any other adjustment of TSC_ADJUST works as expected as long as it stays in the positive range. The direction of the adjustment has no influence either. See the lkml link for further analysis. Yet another proof for the theory that timers are designed by janitors and the underlying (obviously undocumented) mechanisms which allow BIOSes to wreckage them are considered a feature. Well done Intel - NOT! To address this wreckage add the following sanity measures: - If the TSC_ADJUST value on the boot cpu is not 0, set it to 0 - If the TSC_ADJUST value on any cpu is negative, set it to 0 - Prevent the cross package synchronization mechanism from setting negative TSC_ADJUST values. Reported-and-tested-by: Roland Scheidegger <rscheidegger_lists@hispeed.ch> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bruce Schlobohm <bruce.schlobohm@intel.com> Cc: Kevin Stanton <kevin.b.stanton@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Allen Hung <allen_hung@dell.com> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-12-13 20:14:17 +07:00
static void tsc_sanitize_first_cpu(struct tsc_adjust *cur, s64 bootval,
unsigned int cpu, bool bootcpu)
{
/*
* First online CPU in a package stores the boot value in the
* adjustment value. This value might change later via the sync
* mechanism. If that fails we still can yell about boot values not
* being consistent.
*
* On the boot cpu we just force set the ADJUST value to 0 if it's
* non zero. We don't do that on non boot cpus because physical
* hotplug should have set the ADJUST register to a value > 0 so
* the TSC is in sync with the already running cpus.
*/
if (bootcpu && bootval != 0) {
pr_warn(FW_BUG "TSC ADJUST: CPU%u: %lld force to 0\n", cpu,
bootval);
x86/tsc: Force TSC_ADJUST register to value >= zero Roland reported that his DELL T5810 sports a value add BIOS which completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with random negative TSC_ADJUST values, different on all CPUs. That renders the TSC useless because the sycnchronization check fails. Roland tested the new TSC_ADJUST mechanism. While it manages to readjust the TSCs he needs to disable the TSC deadline timer, otherwise the machine just stops booting. Deeper investigation unearthed that the TSC deadline timer is sensitive to the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an interrupt storm caused by the TSC deadline timer. This does not make any sense and it's hard to imagine what kind of hardware wreckage is behind that misfeature, but it's reliably reproducible on other systems which have TSC_ADJUST and TSC deadline timer. While it would be understandable that a big enough negative value which moves the resulting TSC readout into the negative space could have the described effect, this happens even with a adjust value of -1, which keeps the TSC readout definitely in the positive space. The compare register for the TSC deadline timer is set to a positive value larger than the TSC, but despite not having reached the deadline the interrupt is raised immediately. If this happens on the boot CPU, then the machine dies silently because this setup happens before the NMI watchdog is armed. Further experiments showed that any other adjustment of TSC_ADJUST works as expected as long as it stays in the positive range. The direction of the adjustment has no influence either. See the lkml link for further analysis. Yet another proof for the theory that timers are designed by janitors and the underlying (obviously undocumented) mechanisms which allow BIOSes to wreckage them are considered a feature. Well done Intel - NOT! To address this wreckage add the following sanity measures: - If the TSC_ADJUST value on the boot cpu is not 0, set it to 0 - If the TSC_ADJUST value on any cpu is negative, set it to 0 - Prevent the cross package synchronization mechanism from setting negative TSC_ADJUST values. Reported-and-tested-by: Roland Scheidegger <rscheidegger_lists@hispeed.ch> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bruce Schlobohm <bruce.schlobohm@intel.com> Cc: Kevin Stanton <kevin.b.stanton@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Allen Hung <allen_hung@dell.com> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-12-13 20:14:17 +07:00
wrmsrl(MSR_IA32_TSC_ADJUST, 0);
bootval = 0;
}
cur->adjusted = bootval;
}
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
#ifndef CONFIG_SMP
x86/tsc: Force TSC_ADJUST register to value >= zero Roland reported that his DELL T5810 sports a value add BIOS which completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with random negative TSC_ADJUST values, different on all CPUs. That renders the TSC useless because the sycnchronization check fails. Roland tested the new TSC_ADJUST mechanism. While it manages to readjust the TSCs he needs to disable the TSC deadline timer, otherwise the machine just stops booting. Deeper investigation unearthed that the TSC deadline timer is sensitive to the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an interrupt storm caused by the TSC deadline timer. This does not make any sense and it's hard to imagine what kind of hardware wreckage is behind that misfeature, but it's reliably reproducible on other systems which have TSC_ADJUST and TSC deadline timer. While it would be understandable that a big enough negative value which moves the resulting TSC readout into the negative space could have the described effect, this happens even with a adjust value of -1, which keeps the TSC readout definitely in the positive space. The compare register for the TSC deadline timer is set to a positive value larger than the TSC, but despite not having reached the deadline the interrupt is raised immediately. If this happens on the boot CPU, then the machine dies silently because this setup happens before the NMI watchdog is armed. Further experiments showed that any other adjustment of TSC_ADJUST works as expected as long as it stays in the positive range. The direction of the adjustment has no influence either. See the lkml link for further analysis. Yet another proof for the theory that timers are designed by janitors and the underlying (obviously undocumented) mechanisms which allow BIOSes to wreckage them are considered a feature. Well done Intel - NOT! To address this wreckage add the following sanity measures: - If the TSC_ADJUST value on the boot cpu is not 0, set it to 0 - If the TSC_ADJUST value on any cpu is negative, set it to 0 - Prevent the cross package synchronization mechanism from setting negative TSC_ADJUST values. Reported-and-tested-by: Roland Scheidegger <rscheidegger_lists@hispeed.ch> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bruce Schlobohm <bruce.schlobohm@intel.com> Cc: Kevin Stanton <kevin.b.stanton@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Allen Hung <allen_hung@dell.com> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-12-13 20:14:17 +07:00
bool __init tsc_store_and_check_tsc_adjust(bool bootcpu)
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
{
struct tsc_adjust *cur = this_cpu_ptr(&tsc_adjust);
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
s64 bootval;
if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST))
return false;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
rdmsrl(MSR_IA32_TSC_ADJUST, bootval);
cur->bootval = bootval;
cur->nextcheck = jiffies + HZ;
x86/tsc: Force TSC_ADJUST register to value >= zero Roland reported that his DELL T5810 sports a value add BIOS which completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with random negative TSC_ADJUST values, different on all CPUs. That renders the TSC useless because the sycnchronization check fails. Roland tested the new TSC_ADJUST mechanism. While it manages to readjust the TSCs he needs to disable the TSC deadline timer, otherwise the machine just stops booting. Deeper investigation unearthed that the TSC deadline timer is sensitive to the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an interrupt storm caused by the TSC deadline timer. This does not make any sense and it's hard to imagine what kind of hardware wreckage is behind that misfeature, but it's reliably reproducible on other systems which have TSC_ADJUST and TSC deadline timer. While it would be understandable that a big enough negative value which moves the resulting TSC readout into the negative space could have the described effect, this happens even with a adjust value of -1, which keeps the TSC readout definitely in the positive space. The compare register for the TSC deadline timer is set to a positive value larger than the TSC, but despite not having reached the deadline the interrupt is raised immediately. If this happens on the boot CPU, then the machine dies silently because this setup happens before the NMI watchdog is armed. Further experiments showed that any other adjustment of TSC_ADJUST works as expected as long as it stays in the positive range. The direction of the adjustment has no influence either. See the lkml link for further analysis. Yet another proof for the theory that timers are designed by janitors and the underlying (obviously undocumented) mechanisms which allow BIOSes to wreckage them are considered a feature. Well done Intel - NOT! To address this wreckage add the following sanity measures: - If the TSC_ADJUST value on the boot cpu is not 0, set it to 0 - If the TSC_ADJUST value on any cpu is negative, set it to 0 - Prevent the cross package synchronization mechanism from setting negative TSC_ADJUST values. Reported-and-tested-by: Roland Scheidegger <rscheidegger_lists@hispeed.ch> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bruce Schlobohm <bruce.schlobohm@intel.com> Cc: Kevin Stanton <kevin.b.stanton@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Allen Hung <allen_hung@dell.com> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-12-13 20:14:17 +07:00
tsc_sanitize_first_cpu(cur, bootval, smp_processor_id(), bootcpu);
return false;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
}
#else /* !CONFIG_SMP */
/*
* Store and check the TSC ADJUST MSR if available
*/
x86/tsc: Force TSC_ADJUST register to value >= zero Roland reported that his DELL T5810 sports a value add BIOS which completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with random negative TSC_ADJUST values, different on all CPUs. That renders the TSC useless because the sycnchronization check fails. Roland tested the new TSC_ADJUST mechanism. While it manages to readjust the TSCs he needs to disable the TSC deadline timer, otherwise the machine just stops booting. Deeper investigation unearthed that the TSC deadline timer is sensitive to the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an interrupt storm caused by the TSC deadline timer. This does not make any sense and it's hard to imagine what kind of hardware wreckage is behind that misfeature, but it's reliably reproducible on other systems which have TSC_ADJUST and TSC deadline timer. While it would be understandable that a big enough negative value which moves the resulting TSC readout into the negative space could have the described effect, this happens even with a adjust value of -1, which keeps the TSC readout definitely in the positive space. The compare register for the TSC deadline timer is set to a positive value larger than the TSC, but despite not having reached the deadline the interrupt is raised immediately. If this happens on the boot CPU, then the machine dies silently because this setup happens before the NMI watchdog is armed. Further experiments showed that any other adjustment of TSC_ADJUST works as expected as long as it stays in the positive range. The direction of the adjustment has no influence either. See the lkml link for further analysis. Yet another proof for the theory that timers are designed by janitors and the underlying (obviously undocumented) mechanisms which allow BIOSes to wreckage them are considered a feature. Well done Intel - NOT! To address this wreckage add the following sanity measures: - If the TSC_ADJUST value on the boot cpu is not 0, set it to 0 - If the TSC_ADJUST value on any cpu is negative, set it to 0 - Prevent the cross package synchronization mechanism from setting negative TSC_ADJUST values. Reported-and-tested-by: Roland Scheidegger <rscheidegger_lists@hispeed.ch> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bruce Schlobohm <bruce.schlobohm@intel.com> Cc: Kevin Stanton <kevin.b.stanton@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Allen Hung <allen_hung@dell.com> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-12-13 20:14:17 +07:00
bool tsc_store_and_check_tsc_adjust(bool bootcpu)
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
{
struct tsc_adjust *ref, *cur = this_cpu_ptr(&tsc_adjust);
unsigned int refcpu, cpu = smp_processor_id();
struct cpumask *mask;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
s64 bootval;
if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST))
return false;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
rdmsrl(MSR_IA32_TSC_ADJUST, bootval);
cur->bootval = bootval;
cur->nextcheck = jiffies + HZ;
cur->warned = false;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
/*
* Check whether this CPU is the first in a package to come up. In
* this case do not check the boot value against another package
x86/tsc: Force TSC_ADJUST register to value >= zero Roland reported that his DELL T5810 sports a value add BIOS which completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with random negative TSC_ADJUST values, different on all CPUs. That renders the TSC useless because the sycnchronization check fails. Roland tested the new TSC_ADJUST mechanism. While it manages to readjust the TSCs he needs to disable the TSC deadline timer, otherwise the machine just stops booting. Deeper investigation unearthed that the TSC deadline timer is sensitive to the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an interrupt storm caused by the TSC deadline timer. This does not make any sense and it's hard to imagine what kind of hardware wreckage is behind that misfeature, but it's reliably reproducible on other systems which have TSC_ADJUST and TSC deadline timer. While it would be understandable that a big enough negative value which moves the resulting TSC readout into the negative space could have the described effect, this happens even with a adjust value of -1, which keeps the TSC readout definitely in the positive space. The compare register for the TSC deadline timer is set to a positive value larger than the TSC, but despite not having reached the deadline the interrupt is raised immediately. If this happens on the boot CPU, then the machine dies silently because this setup happens before the NMI watchdog is armed. Further experiments showed that any other adjustment of TSC_ADJUST works as expected as long as it stays in the positive range. The direction of the adjustment has no influence either. See the lkml link for further analysis. Yet another proof for the theory that timers are designed by janitors and the underlying (obviously undocumented) mechanisms which allow BIOSes to wreckage them are considered a feature. Well done Intel - NOT! To address this wreckage add the following sanity measures: - If the TSC_ADJUST value on the boot cpu is not 0, set it to 0 - If the TSC_ADJUST value on any cpu is negative, set it to 0 - Prevent the cross package synchronization mechanism from setting negative TSC_ADJUST values. Reported-and-tested-by: Roland Scheidegger <rscheidegger_lists@hispeed.ch> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bruce Schlobohm <bruce.schlobohm@intel.com> Cc: Kevin Stanton <kevin.b.stanton@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Allen Hung <allen_hung@dell.com> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-12-13 20:14:17 +07:00
* because the new package might have been physically hotplugged,
* where TSC_ADJUST is expected to be different. When called on the
* boot CPU topology_core_cpumask() might not be available yet.
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
*/
mask = topology_core_cpumask(cpu);
refcpu = mask ? cpumask_any_but(mask, cpu) : nr_cpu_ids;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
if (refcpu >= nr_cpu_ids) {
x86/tsc: Force TSC_ADJUST register to value >= zero Roland reported that his DELL T5810 sports a value add BIOS which completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with random negative TSC_ADJUST values, different on all CPUs. That renders the TSC useless because the sycnchronization check fails. Roland tested the new TSC_ADJUST mechanism. While it manages to readjust the TSCs he needs to disable the TSC deadline timer, otherwise the machine just stops booting. Deeper investigation unearthed that the TSC deadline timer is sensitive to the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an interrupt storm caused by the TSC deadline timer. This does not make any sense and it's hard to imagine what kind of hardware wreckage is behind that misfeature, but it's reliably reproducible on other systems which have TSC_ADJUST and TSC deadline timer. While it would be understandable that a big enough negative value which moves the resulting TSC readout into the negative space could have the described effect, this happens even with a adjust value of -1, which keeps the TSC readout definitely in the positive space. The compare register for the TSC deadline timer is set to a positive value larger than the TSC, but despite not having reached the deadline the interrupt is raised immediately. If this happens on the boot CPU, then the machine dies silently because this setup happens before the NMI watchdog is armed. Further experiments showed that any other adjustment of TSC_ADJUST works as expected as long as it stays in the positive range. The direction of the adjustment has no influence either. See the lkml link for further analysis. Yet another proof for the theory that timers are designed by janitors and the underlying (obviously undocumented) mechanisms which allow BIOSes to wreckage them are considered a feature. Well done Intel - NOT! To address this wreckage add the following sanity measures: - If the TSC_ADJUST value on the boot cpu is not 0, set it to 0 - If the TSC_ADJUST value on any cpu is negative, set it to 0 - Prevent the cross package synchronization mechanism from setting negative TSC_ADJUST values. Reported-and-tested-by: Roland Scheidegger <rscheidegger_lists@hispeed.ch> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Bruce Schlobohm <bruce.schlobohm@intel.com> Cc: Kevin Stanton <kevin.b.stanton@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Allen Hung <allen_hung@dell.com> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-12-13 20:14:17 +07:00
tsc_sanitize_first_cpu(cur, bootval, smp_processor_id(),
bootcpu);
return false;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
}
ref = per_cpu_ptr(&tsc_adjust, refcpu);
/*
* Compare the boot value and complain if it differs in the
* package.
*/
if (bootval != ref->bootval) {
pr_warn(FW_BUG "TSC ADJUST differs: Reference CPU%u: %lld CPU%u: %lld\n",
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
refcpu, ref->bootval, cpu, bootval);
}
/*
* The TSC_ADJUST values in a package must be the same. If the boot
* value on this newly upcoming CPU differs from the adjustment
* value of the already online CPU in this package, set it to that
* adjusted value.
*/
if (bootval != ref->adjusted) {
pr_warn("TSC ADJUST synchronize: Reference CPU%u: %lld CPU%u: %lld\n",
refcpu, ref->adjusted, cpu, bootval);
cur->adjusted = ref->adjusted;
wrmsrl(MSR_IA32_TSC_ADJUST, ref->adjusted);
}
/*
* We have the TSCs forced to be in sync on this package. Skip sync
* test:
*/
return true;
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
}
/*
* Entry/exit counters that make sure that both CPUs
* run the measurement code at once:
*/
x86: delete __cpuinit usage from all x86 files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. Note that some harmless section mismatch warnings may result, since notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c) are flagged as __cpuinit -- so if we remove the __cpuinit from arch specific callers, we will also get section mismatch warnings. As an intermediate step, we intend to turn the linux/init.h cpuinit content into no-ops as early as possible, since that will get rid of these warnings. In any case, they are temporary and harmless. This removes all the arch/x86 uses of the __cpuinit macros from all C files. x86 only had the one __CPUINIT used in assembly files, and it wasn't paired off with a .previous or a __FINIT, so we can delete it directly w/o any corresponding additional change there. [1] https://lkml.org/lkml/2013/5/20/589 Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: H. Peter Anvin <hpa@linux.intel.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 05:23:59 +07:00
static atomic_t start_count;
static atomic_t stop_count;
static atomic_t skip_test;
static atomic_t test_runs;
/*
* We use a raw spinlock in this exceptional case, because
* we want to have the fastest, inlined, non-debug version
* of a critical section, to be able to prove TSC time-warps:
*/
x86: delete __cpuinit usage from all x86 files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. Note that some harmless section mismatch warnings may result, since notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c) are flagged as __cpuinit -- so if we remove the __cpuinit from arch specific callers, we will also get section mismatch warnings. As an intermediate step, we intend to turn the linux/init.h cpuinit content into no-ops as early as possible, since that will get rid of these warnings. In any case, they are temporary and harmless. This removes all the arch/x86 uses of the __cpuinit macros from all C files. x86 only had the one __CPUINIT used in assembly files, and it wasn't paired off with a .previous or a __FINIT, so we can delete it directly w/o any corresponding additional change there. [1] https://lkml.org/lkml/2013/5/20/589 Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: H. Peter Anvin <hpa@linux.intel.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 05:23:59 +07:00
static arch_spinlock_t sync_lock = __ARCH_SPIN_LOCK_UNLOCKED;
x86: delete __cpuinit usage from all x86 files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. Note that some harmless section mismatch warnings may result, since notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c) are flagged as __cpuinit -- so if we remove the __cpuinit from arch specific callers, we will also get section mismatch warnings. As an intermediate step, we intend to turn the linux/init.h cpuinit content into no-ops as early as possible, since that will get rid of these warnings. In any case, they are temporary and harmless. This removes all the arch/x86 uses of the __cpuinit macros from all C files. x86 only had the one __CPUINIT used in assembly files, and it wasn't paired off with a .previous or a __FINIT, so we can delete it directly w/o any corresponding additional change there. [1] https://lkml.org/lkml/2013/5/20/589 Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: H. Peter Anvin <hpa@linux.intel.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 05:23:59 +07:00
static cycles_t last_tsc;
static cycles_t max_warp;
static int nr_warps;
static int random_warps;
/*
* TSC-warp measurement loop running on both CPUs. This is not called
* if there is no TSC.
*/
static cycles_t check_tsc_warp(unsigned int timeout)
{
cycles_t start, now, prev, end, cur_max_warp = 0;
int i, cur_warps = 0;
start = rdtsc_ordered();
/*
x86/tsc: Reduce the TSC sync check time for core-siblings For each logical CPU that is coming online, we spend 20msec for checking the TSC synchronization. And as this is done sequentially for each logical CPU boot, this time gets added up depending on the number of logical CPU's supported by the platform. Minimize this by using the socket topology information. If the target CPU coming online doesn't have any of its core-siblings online, a timeout of 20msec will be used for the TSC-warp measurement loop. Otherwise a smaller timeout of 2msec will be used, as we have some information about this socket already (and this information grows as we have more and more logical-siblings in that socket). Ideally we should be able to skip the TSC sync check on the other core-siblings, if the first logical CPU in a socket passed the sync test. But as the TSC is per-logical CPU and can potentially be modified wrongly by the bios before the OS boot, TSC sync test for smaller duration should be able to catch such errors. Also this will catch the condition where all the cores in the socket doesn't get reset at the same time. For example, with this modification, time spent in TSC sync checks on a 4 socket 10-core with HT system gets reduced from 1580msec to 212msec. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jack Steiner <steiner@sgi.com> Cc: venki@google.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1328581940.29790.20.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-07 09:32:20 +07:00
* The measurement runs for 'timeout' msecs:
*/
x86/tsc: Reduce the TSC sync check time for core-siblings For each logical CPU that is coming online, we spend 20msec for checking the TSC synchronization. And as this is done sequentially for each logical CPU boot, this time gets added up depending on the number of logical CPU's supported by the platform. Minimize this by using the socket topology information. If the target CPU coming online doesn't have any of its core-siblings online, a timeout of 20msec will be used for the TSC-warp measurement loop. Otherwise a smaller timeout of 2msec will be used, as we have some information about this socket already (and this information grows as we have more and more logical-siblings in that socket). Ideally we should be able to skip the TSC sync check on the other core-siblings, if the first logical CPU in a socket passed the sync test. But as the TSC is per-logical CPU and can potentially be modified wrongly by the bios before the OS boot, TSC sync test for smaller duration should be able to catch such errors. Also this will catch the condition where all the cores in the socket doesn't get reset at the same time. For example, with this modification, time spent in TSC sync checks on a 4 socket 10-core with HT system gets reduced from 1580msec to 212msec. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jack Steiner <steiner@sgi.com> Cc: venki@google.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1328581940.29790.20.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-07 09:32:20 +07:00
end = start + (cycles_t) tsc_khz * timeout;
now = start;
for (i = 0; ; i++) {
/*
* We take the global lock, measure TSC, save the
* previous TSC that was measured (possibly on
* another CPU) and update the previous TSC timestamp.
*/
arch_spin_lock(&sync_lock);
prev = last_tsc;
now = rdtsc_ordered();
last_tsc = now;
arch_spin_unlock(&sync_lock);
/*
* Be nice every now and then (and also check whether
* measurement is done [we also insert a 10 million
* loops safety exit, so we dont lock up in case the
* TSC readout is totally broken]):
*/
if (unlikely(!(i & 7))) {
if (now > end || i > 10000000)
break;
cpu_relax();
touch_nmi_watchdog();
}
/*
* Outside the critical section we can now see whether
* we saw a time-warp of the TSC going backwards:
*/
if (unlikely(prev > now)) {
arch_spin_lock(&sync_lock);
max_warp = max(max_warp, prev - now);
cur_max_warp = max_warp;
/*
* Check whether this bounces back and forth. Only
* one CPU should observe time going backwards.
*/
if (cur_warps != nr_warps)
random_warps++;
nr_warps++;
cur_warps = nr_warps;
arch_spin_unlock(&sync_lock);
}
}
WARN(!(now-start),
"Warning: zero tsc calibration delta: %Ld [max: %Ld]\n",
now-start, end-start);
return cur_max_warp;
}
x86/tsc: Reduce the TSC sync check time for core-siblings For each logical CPU that is coming online, we spend 20msec for checking the TSC synchronization. And as this is done sequentially for each logical CPU boot, this time gets added up depending on the number of logical CPU's supported by the platform. Minimize this by using the socket topology information. If the target CPU coming online doesn't have any of its core-siblings online, a timeout of 20msec will be used for the TSC-warp measurement loop. Otherwise a smaller timeout of 2msec will be used, as we have some information about this socket already (and this information grows as we have more and more logical-siblings in that socket). Ideally we should be able to skip the TSC sync check on the other core-siblings, if the first logical CPU in a socket passed the sync test. But as the TSC is per-logical CPU and can potentially be modified wrongly by the bios before the OS boot, TSC sync test for smaller duration should be able to catch such errors. Also this will catch the condition where all the cores in the socket doesn't get reset at the same time. For example, with this modification, time spent in TSC sync checks on a 4 socket 10-core with HT system gets reduced from 1580msec to 212msec. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jack Steiner <steiner@sgi.com> Cc: venki@google.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1328581940.29790.20.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-07 09:32:20 +07:00
/*
* If the target CPU coming online doesn't have any of its core-siblings
* online, a timeout of 20msec will be used for the TSC-warp measurement
* loop. Otherwise a smaller timeout of 2msec will be used, as we have some
* information about this socket already (and this information grows as we
* have more and more logical-siblings in that socket).
*
* Ideally we should be able to skip the TSC sync check on the other
* core-siblings, if the first logical CPU in a socket passed the sync test.
* But as the TSC is per-logical CPU and can potentially be modified wrongly
* by the bios, TSC sync test for smaller duration should be able
* to catch such errors. Also this will catch the condition where all the
* cores in the socket doesn't get reset at the same time.
*/
static inline unsigned int loop_timeout(int cpu)
{
return (cpumask_weight(topology_core_cpumask(cpu)) > 1) ? 2 : 20;
x86/tsc: Reduce the TSC sync check time for core-siblings For each logical CPU that is coming online, we spend 20msec for checking the TSC synchronization. And as this is done sequentially for each logical CPU boot, this time gets added up depending on the number of logical CPU's supported by the platform. Minimize this by using the socket topology information. If the target CPU coming online doesn't have any of its core-siblings online, a timeout of 20msec will be used for the TSC-warp measurement loop. Otherwise a smaller timeout of 2msec will be used, as we have some information about this socket already (and this information grows as we have more and more logical-siblings in that socket). Ideally we should be able to skip the TSC sync check on the other core-siblings, if the first logical CPU in a socket passed the sync test. But as the TSC is per-logical CPU and can potentially be modified wrongly by the bios before the OS boot, TSC sync test for smaller duration should be able to catch such errors. Also this will catch the condition where all the cores in the socket doesn't get reset at the same time. For example, with this modification, time spent in TSC sync checks on a 4 socket 10-core with HT system gets reduced from 1580msec to 212msec. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jack Steiner <steiner@sgi.com> Cc: venki@google.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1328581940.29790.20.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-07 09:32:20 +07:00
}
/*
* Source CPU calls into this - it waits for the freshly booted
* target CPU to arrive and then starts the measurement:
*/
x86: delete __cpuinit usage from all x86 files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. Note that some harmless section mismatch warnings may result, since notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c) are flagged as __cpuinit -- so if we remove the __cpuinit from arch specific callers, we will also get section mismatch warnings. As an intermediate step, we intend to turn the linux/init.h cpuinit content into no-ops as early as possible, since that will get rid of these warnings. In any case, they are temporary and harmless. This removes all the arch/x86 uses of the __cpuinit macros from all C files. x86 only had the one __CPUINIT used in assembly files, and it wasn't paired off with a .previous or a __FINIT, so we can delete it directly w/o any corresponding additional change there. [1] https://lkml.org/lkml/2013/5/20/589 Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: H. Peter Anvin <hpa@linux.intel.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 05:23:59 +07:00
void check_tsc_sync_source(int cpu)
{
int cpus = 2;
/*
* No need to check if we already know that the TSC is not
* synchronized or if we have no TSC.
*/
if (unsynchronized_tsc())
return;
/*
* Set the maximum number of test runs to
* 1 if the CPU does not provide the TSC_ADJUST MSR
* 3 if the MSR is available, so the target can try to adjust
*/
if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST))
atomic_set(&test_runs, 1);
else
atomic_set(&test_runs, 3);
retry:
/*
* Wait for the target to start or to skip the test:
*/
while (atomic_read(&start_count) != cpus - 1) {
if (atomic_read(&skip_test) > 0) {
atomic_set(&skip_test, 0);
return;
}
cpu_relax();
}
/*
* Trigger the target to continue into the measurement too:
*/
atomic_inc(&start_count);
x86/tsc: Reduce the TSC sync check time for core-siblings For each logical CPU that is coming online, we spend 20msec for checking the TSC synchronization. And as this is done sequentially for each logical CPU boot, this time gets added up depending on the number of logical CPU's supported by the platform. Minimize this by using the socket topology information. If the target CPU coming online doesn't have any of its core-siblings online, a timeout of 20msec will be used for the TSC-warp measurement loop. Otherwise a smaller timeout of 2msec will be used, as we have some information about this socket already (and this information grows as we have more and more logical-siblings in that socket). Ideally we should be able to skip the TSC sync check on the other core-siblings, if the first logical CPU in a socket passed the sync test. But as the TSC is per-logical CPU and can potentially be modified wrongly by the bios before the OS boot, TSC sync test for smaller duration should be able to catch such errors. Also this will catch the condition where all the cores in the socket doesn't get reset at the same time. For example, with this modification, time spent in TSC sync checks on a 4 socket 10-core with HT system gets reduced from 1580msec to 212msec. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jack Steiner <steiner@sgi.com> Cc: venki@google.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1328581940.29790.20.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-07 09:32:20 +07:00
check_tsc_warp(loop_timeout(cpu));
while (atomic_read(&stop_count) != cpus-1)
cpu_relax();
/*
* If the test was successful set the number of runs to zero and
* stop. If not, decrement the number of runs an check if we can
* retry. In case of random warps no retry is attempted.
*/
if (!nr_warps) {
atomic_set(&test_runs, 0);
pr_debug("TSC synchronization [CPU#%d -> CPU#%d]: passed\n",
smp_processor_id(), cpu);
} else if (atomic_dec_and_test(&test_runs) || random_warps) {
/* Force it to 0 if random warps brought us here */
atomic_set(&test_runs, 0);
pr_warning("TSC synchronization [CPU#%d -> CPU#%d]:\n",
smp_processor_id(), cpu);
pr_warning("Measured %Ld cycles TSC warp between CPUs, "
"turning off TSC clock.\n", max_warp);
if (random_warps)
pr_warning("TSC warped randomly between CPUs\n");
mark_tsc_unstable("check_tsc_sync_source failed");
}
x86: fix: s2ram + P4 + tsc = annoyance s2ram recently became useful here, except for the kernel's annoying habit of disabling my P4's perfectly good TSC. [ 107.894470] CPU 1 is now offline [ 107.894474] SMP alternatives: switching to UP code [ 107.895832] CPU0 attaching sched-domain: [ 107.895836] domain 0: span 1 [ 107.895838] groups: 1 [ 107.896097] CPU1 is down [ 3.726156] Intel machine check architecture supported. [ 3.726165] Intel machine check reporting enabled on CPU#0. [ 3.726167] CPU0: Intel P4/Xeon Extended MCE MSRs (12) available [ 3.726170] CPU0: Thermal monitoring enabled [ 3.726175] Back to C! [ 3.726708] Force enabled HPET at resume [ 3.726775] Enabling non-boot CPUs ... [ 3.727049] CPU0 attaching NULL sched-domain. [ 3.727165] SMP alternatives: switching to SMP code [ 3.727858] Booting processor 1/1 eip 3000 [ 3.727862] CPU 1 irqstacks, hard=b042f000 soft=b042d000 [ 3.738173] Initializing CPU#1 [ 3.798912] Calibrating delay using timer specific routine.. 5986.12 BogoMIPS (lpj=2993061) [ 3.798920] CPU: After generic identify, caps: bfebfbff 00000000 00000000 00000000 00004400 00000000 00000000 00000000 [ 3.798931] CPU: Trace cache: 12K uops, L1 D cache: 8K [ 3.798934] CPU: L2 cache: 512K [ 3.798936] CPU: Physical Processor ID: 0 [ 3.798938] CPU: After all inits, caps: bfebfbff 00000000 00000000 0000b080 00004400 00000000 00000000 00000000 [ 3.798946] Intel machine check architecture supported. [ 3.798952] Intel machine check reporting enabled on CPU#1. [ 3.798955] CPU1: Intel P4/Xeon Extended MCE MSRs (12) available [ 3.798959] CPU1: Thermal monitoring enabled [ 3.799161] CPU1: Intel(R) Pentium(R) 4 CPU 3.00GHz stepping 09 [ 3.799187] checking TSC synchronization [CPU#0 -> CPU#1]: [ 3.819181] Measured 63588552840 cycles TSC warp between CPUs, turning off TSC clock. [ 3.819184] Marking TSC unstable due to: check_tsc_sync_source failed. If check_tsc_warp() is called after initial boot, and the TSC has in the meantime been set (BIOS, user, silicon, elves) to a value lower than the last stored/stale value, we blame the TSC. Reset to pristine condition after every test. Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30 19:30:04 +07:00
/*
* Reset it - just in case we boot another CPU later:
*/
atomic_set(&start_count, 0);
random_warps = 0;
x86: fix: s2ram + P4 + tsc = annoyance s2ram recently became useful here, except for the kernel's annoying habit of disabling my P4's perfectly good TSC. [ 107.894470] CPU 1 is now offline [ 107.894474] SMP alternatives: switching to UP code [ 107.895832] CPU0 attaching sched-domain: [ 107.895836] domain 0: span 1 [ 107.895838] groups: 1 [ 107.896097] CPU1 is down [ 3.726156] Intel machine check architecture supported. [ 3.726165] Intel machine check reporting enabled on CPU#0. [ 3.726167] CPU0: Intel P4/Xeon Extended MCE MSRs (12) available [ 3.726170] CPU0: Thermal monitoring enabled [ 3.726175] Back to C! [ 3.726708] Force enabled HPET at resume [ 3.726775] Enabling non-boot CPUs ... [ 3.727049] CPU0 attaching NULL sched-domain. [ 3.727165] SMP alternatives: switching to SMP code [ 3.727858] Booting processor 1/1 eip 3000 [ 3.727862] CPU 1 irqstacks, hard=b042f000 soft=b042d000 [ 3.738173] Initializing CPU#1 [ 3.798912] Calibrating delay using timer specific routine.. 5986.12 BogoMIPS (lpj=2993061) [ 3.798920] CPU: After generic identify, caps: bfebfbff 00000000 00000000 00000000 00004400 00000000 00000000 00000000 [ 3.798931] CPU: Trace cache: 12K uops, L1 D cache: 8K [ 3.798934] CPU: L2 cache: 512K [ 3.798936] CPU: Physical Processor ID: 0 [ 3.798938] CPU: After all inits, caps: bfebfbff 00000000 00000000 0000b080 00004400 00000000 00000000 00000000 [ 3.798946] Intel machine check architecture supported. [ 3.798952] Intel machine check reporting enabled on CPU#1. [ 3.798955] CPU1: Intel P4/Xeon Extended MCE MSRs (12) available [ 3.798959] CPU1: Thermal monitoring enabled [ 3.799161] CPU1: Intel(R) Pentium(R) 4 CPU 3.00GHz stepping 09 [ 3.799187] checking TSC synchronization [CPU#0 -> CPU#1]: [ 3.819181] Measured 63588552840 cycles TSC warp between CPUs, turning off TSC clock. [ 3.819184] Marking TSC unstable due to: check_tsc_sync_source failed. If check_tsc_warp() is called after initial boot, and the TSC has in the meantime been set (BIOS, user, silicon, elves) to a value lower than the last stored/stale value, we blame the TSC. Reset to pristine condition after every test. Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30 19:30:04 +07:00
nr_warps = 0;
max_warp = 0;
last_tsc = 0;
/*
* Let the target continue with the bootup:
*/
atomic_inc(&stop_count);
/*
* Retry, if there is a chance to do so.
*/
if (atomic_read(&test_runs) > 0)
goto retry;
}
/*
* Freshly booted CPUs call into this:
*/
x86: delete __cpuinit usage from all x86 files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. Note that some harmless section mismatch warnings may result, since notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c) are flagged as __cpuinit -- so if we remove the __cpuinit from arch specific callers, we will also get section mismatch warnings. As an intermediate step, we intend to turn the linux/init.h cpuinit content into no-ops as early as possible, since that will get rid of these warnings. In any case, they are temporary and harmless. This removes all the arch/x86 uses of the __cpuinit macros from all C files. x86 only had the one __CPUINIT used in assembly files, and it wasn't paired off with a .previous or a __FINIT, so we can delete it directly w/o any corresponding additional change there. [1] https://lkml.org/lkml/2013/5/20/589 Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: H. Peter Anvin <hpa@linux.intel.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 05:23:59 +07:00
void check_tsc_sync_target(void)
{
struct tsc_adjust *cur = this_cpu_ptr(&tsc_adjust);
unsigned int cpu = smp_processor_id();
cycles_t cur_max_warp, gbl_max_warp;
int cpus = 2;
/* Also aborts if there is no TSC. */
if (unsynchronized_tsc())
return;
/*
* Store, verify and sanitize the TSC adjust register. If
* successful skip the test.
*
* The test is also skipped when the TSC is marked reliable. This
* is true for SoCs which have no fallback clocksource. On these
* SoCs the TSC is frequency synchronized, but still the TSC ADJUST
* register might have been wreckaged by the BIOS..
*/
if (tsc_store_and_check_tsc_adjust(false) || tsc_clocksource_reliable) {
atomic_inc(&skip_test);
return;
}
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
retry:
/*
* Register this CPU's participation and wait for the
* source CPU to start the measurement:
*/
atomic_inc(&start_count);
while (atomic_read(&start_count) != cpus)
cpu_relax();
cur_max_warp = check_tsc_warp(loop_timeout(cpu));
/*
* Store the maximum observed warp value for a potential retry:
*/
gbl_max_warp = max_warp;
/*
* Ok, we are done:
*/
atomic_inc(&stop_count);
/*
* Wait for the source CPU to print stuff:
*/
while (atomic_read(&stop_count) != cpus)
cpu_relax();
/*
* Reset it for the next sync test:
*/
atomic_set(&stop_count, 0);
/*
* Check the number of remaining test runs. If not zero, the test
* failed and a retry with adjusted TSC is possible. If zero the
* test was either successful or failed terminally.
*/
if (!atomic_read(&test_runs))
return;
/*
* If the warp value of this CPU is 0, then the other CPU
* observed time going backwards so this TSC was ahead and
* needs to move backwards.
*/
if (!cur_max_warp)
cur_max_warp = -gbl_max_warp;
/*
* Add the result to the previous adjustment value.
*
* The adjustement value is slightly off by the overhead of the
* sync mechanism (observed values are ~200 TSC cycles), but this
* really depends on CPU, node distance and frequency. So
* compensating for this is hard to get right. Experiments show
* that the warp is not longer detectable when the observed warp
* value is used. In the worst case the adjustment needs to go
* through a 3rd run for fine tuning.
*/
cur->adjusted += cur_max_warp;
pr_warn("TSC ADJUST compensate: CPU%u observed %lld warp. Adjust: %lld\n",
cpu, cur_max_warp, cur->adjusted);
wrmsrl(MSR_IA32_TSC_ADJUST, cur->adjusted);
goto retry;
}
x86/tsc: Store and check TSC ADJUST MSR The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful in a two aspects: 1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the cycles spent by storing the TSC value at SMM entry and restoring it at SMM exit. On affected machines the TSCs run slowly out of sync up to the point where the clocksource watchdog (if available) detects it. The TSC_ADJUST MSR allows to detect the TSC modification before that and eventually restore it. This is also important for SoCs which have no watchdog clocksource and therefore TSC wreckage cannot be detected and acted upon. 2) All threads in a package are required to have the same TSC_ADJUST value. Broken BIOSes break that and as a result the TSC synchronization check fails. The TSC_ADJUST MSR allows to detect the deviation when a CPU comes online. If detected set it to the value of an already online CPU in the same package. This also allows to reduce the number of sync tests because with that in place the test is only required for the first CPU in a package. In principle all CPUs in a system should have the same TSC_ADJUST value even across packages, but with physical CPU hotplug this assumption is not true because the TSC starts with power on, so physical hotplug has to do some trickery to bring the TSC into sync with already running packages, which requires to use an TSC_ADJUST value different from CPUs which got powered earlier. A final enhancement is the opportunity to compensate for unsynced TSCs accross nodes at boot time and make the TSC usable that way. It won't help for TSCs which run apart due to frequency skew between packages, but this gets detected by the clocksource watchdog later. The first step toward this is to store the TSC_ADJUST value of a starting CPU and compare it with the value of an already online CPU in the same package. If they differ, emit a warning and adjust it to the reference value. The !SMP version just stores the boot value for later verification. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-19 20:47:36 +07:00
#endif /* CONFIG_SMP */