We currently schedule a soft timer every time we exit the guest if the
timer did not expire while running the guest. This is really not
necessary, because the only work we do in the timer work function is to
kick the vcpu.
Kicking the vcpu does two things:
(1) If the vpcu thread is on a waitqueue, make it runnable and remove it
from the waitqueue.
(2) If the vcpu is running on a different physical CPU from the one
doing the kick, it sends a reschedule IPI.
The second case cannot happen, because the soft timer is only ever
scheduled when the vcpu is not running. The first case is only relevant
when the vcpu thread is on a waitqueue, which is only the case when the
vcpu thread has called kvm_vcpu_block().
Therefore, we only need to make sure a timer is scheduled for
kvm_vcpu_block(), which we do by encapsulating all calls to
kvm_vcpu_block() with kvm_timer_{un}schedule calls.
Additionally, we only schedule a soft timer if the timer is enabled and
unmasked, since it is useless otherwise.
Note that theoretically userspace can use the SET_ONE_REG interface to
change registers that should cause the timer to fire, even if the vcpu
is blocked without a scheduled timer, but this case was not supported
before this patch and we leave it for future work for now.
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
We have an interesting issue when the guest disables the timer interrupt
on the VGIC, which happens when turning VCPUs off using PSCI, for
example.
The problem is that because the guest disables the virtual interrupt at
the VGIC level, we never inject interrupts to the guest and therefore
never mark the interrupt as active on the physical distributor. The
host also never takes the timer interrupt (we only use the timer device
to trigger a guest exit and everything else is done in software), so the
interrupt does not become active through normal means.
The result is that we keep entering the guest with a programmed timer
that will always fire as soon as we context switch the hardware timer
state and run the guest, preventing forward progress for the VCPU.
Since the active state on the physical distributor is really part of the
timer logic, it is the job of our virtual arch timer driver to manage
this state.
The timer->map->active boolean field indicates whether we have signalled
this interrupt to the vgic and if that interrupt is still pending or
active. As long as that is the case, the hardware doesn't have to
generate physical interrupts and therefore we mark the interrupt as
active on the physical distributor.
We also have to restore the pending state of an interrupt that was
queued to an LR but was retired from the LR for some reason, while
remaining pending in the LR.
Cc: Marc Zyngier <marc.zyngier@arm.com>
Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Provide a better quality of implementation and be architecture compliant
on ARMv7 for the architected timer by resetting the CNTV_CTL to 0 on
reset of the timer.
This change alone fixes the UEFI reset issue reported by Laszlo back in
February.
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Drew Jones <drjones@redhat.com>
Cc: Wei Huang <wei@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
In order to remove the crude hack where we sneak the masked bit
into the timer's control register, make use of the phys_irq_map
API control the active state of the interrupt.
This causes some limited changes to allow for potential error
propagation.
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
When a VCPU is no longer running, we currently check to see if it has a
timer scheduled in the future, and if it does, we schedule a host
hrtimer to notify is in case the timer expires while the VCPU is still
not running. When the hrtimer fires, we mask the guest's timer and
inject the timer IRQ (still relying on the guest unmasking the time when
it receives the IRQ).
This is all good and fine, but when migration a VM (checkpoint/restore)
this introduces a race. It is unlikely, but possible, for the following
sequence of events to happen:
1. Userspace stops the VM
2. Hrtimer for VCPU is scheduled
3. Userspace checkpoints the VGIC state (no pending timer interrupts)
4. The hrtimer fires, schedules work in a workqueue
5. Workqueue function runs, masks the timer and injects timer interrupt
6. Userspace checkpoints the timer state (timer masked)
At restore time, you end up with a masked timer without any timer
interrupts and your guest halts never receiving timer interrupts.
Fix this by only kicking the VCPU in the workqueue function, and sample
the expired state of the timer when entering the guest again and inject
the interrupt and mask the timer only then.
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
The current timecounter implementation will drop a variable amount
of resolution, depending on the magnitude of the time delta. In
other words, reading the clock too often or too close to a time
stamp conversion will introduce errors into the time values. This
patch fixes the issue by introducing a fractional nanosecond field
that accumulates the low order bits.
Reported-by: Janusz Użycki <j.uzycki@elproma.com.pl>
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It is curently possible to run a VM with architected timers support
without creating an in-kernel VGIC, which will result in interrupts from
the virtual timer going nowhere.
To address this issue, move the architected timers initialization to the
time when we run a VCPU for the first time, and then only initialize
(and enable) the architected timers if we have a properly created and
initialized in-kernel VGIC.
When injecting interrupts from the virtual timer to the vgic, the
current setup should ensure that this never calls an on-demand init of
the VGIC, which is the only call path that could return an error from
kvm_vgic_inject_irq(), so capture the return value and raise a warning
if there's an error there.
We also change the kvm_timer_init() function from returning an int to be
a void function, since the function always succeeds.
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Commit 8146875de7 (arm, kvm: Fix CPU hotplug callback registration)
holds the lock before calling the two functions:
kvm_vgic_hyp_init()
kvm_timer_hyp_init()
and both the two functions are calling register_cpu_notifier()
to register cpu notifier, so cause double lock on cpu_add_remove_lock.
Considered that both two functions are only called inside
kvm_arch_init() with holding cpu_add_remove_lock, so simply use
__register_cpu_notifier() to fix the problem.
Fixes: 8146875de7 (arm, kvm: Fix CPU hotplug callback registration)
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
For migration to work we need to save (and later restore) the state of
each core's virtual generic timer.
Since this is per VCPU, we can use the [gs]et_one_reg ioctl and export
the three needed registers (control, counter, compare value).
Though they live in cp15 space, we don't use the existing list, since
they need special accessor functions and the arch timer is optional.
Acked-by: Marc Zynger <marc.zyngier@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
On the x86 side, there are some optimizations and documentation updates.
The big ARM/KVM change for 3.11, support for AArch64, will come through
Catalin Marinas's tree. s390 and PPC have misc cleanups and bugfixes.
There is a conflict due to "s390/pgtable: fix ipte notify bit" having
entered 3.10 through Martin Schwidefsky's s390 tree. This pull request
has additional changes on top, so this tree's version is the correct one.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull KVM fixes from Paolo Bonzini:
"On the x86 side, there are some optimizations and documentation
updates. The big ARM/KVM change for 3.11, support for AArch64, will
come through Catalin Marinas's tree. s390 and PPC have misc cleanups
and bugfixes"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (87 commits)
KVM: PPC: Ignore PIR writes
KVM: PPC: Book3S PR: Invalidate SLB entries properly
KVM: PPC: Book3S PR: Allow guest to use 1TB segments
KVM: PPC: Book3S PR: Don't keep scanning HPTEG after we find a match
KVM: PPC: Book3S PR: Fix invalidation of SLB entry 0 on guest entry
KVM: PPC: Book3S PR: Fix proto-VSID calculations
KVM: PPC: Guard doorbell exception with CONFIG_PPC_DOORBELL
KVM: Fix RTC interrupt coalescing tracking
kvm: Add a tracepoint write_tsc_offset
KVM: MMU: Inform users of mmio generation wraparound
KVM: MMU: document fast invalidate all mmio sptes
KVM: MMU: document fast invalidate all pages
KVM: MMU: document fast page fault
KVM: MMU: document mmio page fault
KVM: MMU: document write_flooding_count
KVM: MMU: document clear_spte_count
KVM: MMU: drop kvm_mmu_zap_mmio_sptes
KVM: MMU: init kvm generation close to mmio wrap-around value
KVM: MMU: add tracepoint for check_mmio_spte
KVM: MMU: fast invalidate all mmio sptes
...
The arch_timer irq numbers (or PPI numbers) are implementation dependent,
so the host virtual timer irq number can be different from guest virtual
timer irq number.
This patch ensures that host virtual timer irq number is read from DTB and
guest virtual timer irq is determined based on vcpu target type.
Signed-off-by: Anup Patel <anup.patel@linaro.org>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
Signed-off-by: Christoffer Dall <cdall@cs.columbia.edu>
As KVM/arm64 is looming on the horizon, it makes sense to move some
of the common code to a single location in order to reduce duplication.
The code could live anywhere. Actually, most of KVM is already built
with a bunch of ugly ../../.. hacks in the various Makefiles, so we're
not exactly talking about style here. But maybe it is time to start
moving into a less ugly direction.
The include files must be in a "public" location, as they are accessed
from non-KVM files (arch/arm/kernel/asm-offsets.c).
For this purpose, introduce two new locations:
- virt/kvm/arm/ : x86 and ia64 already share the ioapic code in
virt/kvm, so this could be seen as a (very ugly) precedent.
- include/kvm/ : there is already an include/xen, and while the
intent is slightly different, this seems as good a location as
any
Eventually, we should probably have independant Makefiles at every
levels (just like everywhere else in the kernel), but this is just
the first step.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
