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KVM: arm64: Refuse to run VCPU if the PMU doesn't match the physical CPU

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Userspace can assign a PMU to a VCPU with the KVM_ARM_VCPU_PMU_V3_SET_PMU
device ioctl. If the VCPU is scheduled on a physical CPU which has a
different PMU, the perf events needed to emulate a guest PMU won't be
scheduled in and the guest performance counters will stop counting. Treat
it as an userspace error and refuse to run the VCPU in this situation.

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220127161759.53553-7-alexandru.elisei@arm.com
This commit is contained in:
Alexandru Elisei
2022-01-27 16:17:59 +00:00
committed by Marc Zyngier
parent 6ee7fca2a4
commit 583cda1b0e
5 changed files with 38 additions and 1 deletions
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6
Documentation/virt/kvm/devices/vcpu.rst
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@@ -131,7 +131,11 @@ if a PMU event filter is already present.
Note that KVM will not make any attempts to run the VCPU on the physical CPUs
associated with the PMU specified by this attribute. This is entirely left to
userspace.
userspace. However, attempting to run the VCPU on a physical CPU not supported
by the PMU will fail and KVM_RUN will return with
exit_reason = KVM_EXIT_FAIL_ENTRY and populate the fail_entry struct by setting
hardare_entry_failure_reason field to KVM_EXIT_FAIL_ENTRY_CPU_UNSUPPORTED and
the cpu field to the processor id.
2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
=================================