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5861381d48
The current handling of MSR_IA32_ENERGY_PERF_BIAS in the kernel is
problematic, because it may cause changes made by user space to that
MSR (with the help of the x86_energy_perf_policy tool, for example)
to be lost every time a CPU goes offline and then back online as well
as during system-wide power management transitions into sleep states
and back into the working state.
The first problem is that if the current EPB value for a CPU going
online is 0 ('performance'), the kernel will change it to 6 ('normal')
regardless of whether or not this is the first bring-up of that CPU.
That also happens during system-wide resume from sleep states
(including, but not limited to, hibernation). However, the EPB may
have been adjusted by user space this way and the kernel should not
blindly override that setting.
The second problem is that if the platform firmware resets the EPB
values for any CPUs during system-wide resume from a sleep state,
the kernel will not restore their previous EPB values that may
have been set by user space before the preceding system-wide
suspend transition. Again, that behavior may at least be confusing
from the user space perspective.
In order to address these issues, rework the handling of
MSR_IA32_ENERGY_PERF_BIAS so that the EPB value is saved on CPU
offline and restored on CPU online as well as (for the boot CPU)
during the syscore stages of system-wide suspend and resume
transitions, respectively.
However, retain the policy by which the EPB is set to 6 ('normal')
on the first bring-up of each CPU if its initial value is 0, based
on the observation that 0 may mean 'not initialized' just as well as
'performance' in that case.
While at it, move the MSR_IA32_ENERGY_PERF_BIAS handling code into
a separate file and document it in Documentation/admin-guide.
Fixes: abe48b1082 (x86, intel, power: Initialize MSR_IA32_ENERGY_PERF_BIAS)
Fixes: b51ef52df7 (x86/cpu: Restore MSR_IA32_ENERGY_PERF_BIAS after resume)
Reported-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
66 lines
2.0 KiB
C
66 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef ARCH_X86_CPU_H
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#define ARCH_X86_CPU_H
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/* attempt to consolidate cpu attributes */
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struct cpu_dev {
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const char *c_vendor;
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/* some have two possibilities for cpuid string */
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const char *c_ident[2];
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void (*c_early_init)(struct cpuinfo_x86 *);
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void (*c_bsp_init)(struct cpuinfo_x86 *);
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void (*c_init)(struct cpuinfo_x86 *);
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void (*c_identify)(struct cpuinfo_x86 *);
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void (*c_detect_tlb)(struct cpuinfo_x86 *);
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int c_x86_vendor;
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#ifdef CONFIG_X86_32
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/* Optional vendor specific routine to obtain the cache size. */
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unsigned int (*legacy_cache_size)(struct cpuinfo_x86 *,
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unsigned int);
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/* Family/stepping-based lookup table for model names. */
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struct legacy_cpu_model_info {
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int family;
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const char *model_names[16];
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} legacy_models[5];
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#endif
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};
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struct _tlb_table {
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unsigned char descriptor;
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char tlb_type;
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unsigned int entries;
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/* unsigned int ways; */
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char info[128];
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};
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#define cpu_dev_register(cpu_devX) \
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static const struct cpu_dev *const __cpu_dev_##cpu_devX __used \
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__attribute__((__section__(".x86_cpu_dev.init"))) = \
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&cpu_devX;
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extern const struct cpu_dev *const __x86_cpu_dev_start[],
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*const __x86_cpu_dev_end[];
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extern void get_cpu_cap(struct cpuinfo_x86 *c);
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extern void get_cpu_address_sizes(struct cpuinfo_x86 *c);
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extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
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extern void init_scattered_cpuid_features(struct cpuinfo_x86 *c);
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extern void init_intel_cacheinfo(struct cpuinfo_x86 *c);
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extern void init_amd_cacheinfo(struct cpuinfo_x86 *c);
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extern void init_hygon_cacheinfo(struct cpuinfo_x86 *c);
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extern void detect_num_cpu_cores(struct cpuinfo_x86 *c);
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extern int detect_extended_topology_early(struct cpuinfo_x86 *c);
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extern int detect_extended_topology(struct cpuinfo_x86 *c);
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extern int detect_ht_early(struct cpuinfo_x86 *c);
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extern void detect_ht(struct cpuinfo_x86 *c);
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unsigned int aperfmperf_get_khz(int cpu);
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extern void x86_spec_ctrl_setup_ap(void);
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#endif /* ARCH_X86_CPU_H */
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