[PATCH v2 0/2] KVM: arm64: PMU: Preserve vPMC registers properly on migration

[PATCH v2 0/2] KVM: arm64: PMU: Preserve vPMC registers properly on migration

[Reiji Watanabe]

The series fixes two problems in preserving vPMU counter (vPMC)
registers (PMCCNTR_EL0/PMEVCNTR<n>_EL0) during migration.

One of the problems is that KVM may not return the current values
of the vPMC registers for KVM_GET_ONE_REG.

The other one might cause KVM to reset the vPMC registers on the
first KVM_RUN on the destination. This is because userspace might
save PMCR_EL0 with PMCR_EL0.{C,P} bits set on the source, and
restore it on the destination.

See patch-1 and patch-2 for details on these issues respectively.

The series is based on v6.3-rc2.

v2:
 - Collect Marc's r-b tags (Thank you!)
 - Added "Fixes:" tags
 - Added Cc: to stable
 - Cosmetics change (remove one line break in kvm_pmu_handle_pmcr())

v1: https://lore.kernel.org/all/20230302055033.3081456-1-reijiw@google.com/

Reiji Watanabe (2):
  KVM: arm64: PMU: Fix GET_ONE_REG for vPMC regs to return the current
    value
  KVM: arm64: PMU: Don't save PMCR_EL0.{C,P} for the vCPU

 arch/arm64/kvm/pmu-emul.c |  3 ++-
 arch/arm64/kvm/sys_regs.c | 21 +++++++++++++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)


base-commit: eeac8ede17557680855031c6f305ece2378af326
-- 
2.40.0.rc1.284.g88254d51c5-goog

Re: [PATCH v2 0/2] KVM: arm64: PMU: Preserve vPMC registers properly on migration

[Oliver Upton]

Hi Reiji,

On Sun, Mar 12, 2023 at 08:29:03PM -0700, Reiji Watanabe wrote:
> The series fixes two problems in preserving vPMU counter (vPMC)
> registers (PMCCNTR_EL0/PMEVCNTR<n>_EL0) during migration.
> 
> One of the problems is that KVM may not return the current values
> of the vPMC registers for KVM_GET_ONE_REG.
> 
> The other one might cause KVM to reset the vPMC registers on the
> first KVM_RUN on the destination. This is because userspace might
> save PMCR_EL0 with PMCR_EL0.{C,P} bits set on the source, and
> restore it on the destination.
> 
> See patch-1 and patch-2 for details on these issues respectively.
> 
> The series is based on v6.3-rc2.
> 
> v2:
>  - Collect Marc's r-b tags (Thank you!)
>  - Added "Fixes:" tags
>  - Added Cc: to stable
>  - Cosmetics change (remove one line break in kvm_pmu_handle_pmcr())
> 
> v1: https://lore.kernel.org/all/20230302055033.3081456-1-reijiw@google.com/
> 
> Reiji Watanabe (2):
>   KVM: arm64: PMU: Fix GET_ONE_REG for vPMC regs to return the current
>     value
>   KVM: arm64: PMU: Don't save PMCR_EL0.{C,P} for the vCPU

I received both of these patches as indepentent emails instead of replies to
the cover letter (i.e. In-Reply-To header is missing). I was able to find
both patches but just wanted to let you know so you can debug your tooling.

-- 
Thanks,
Oliver