On Thu, Jan 4, 2024 at 8:33 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> PMU fixes and cleanups. The highlight is a fix for a double-overflow PMI bug
> when KVM manually emulates counter events, which was made mostly benign by
> commit a16eb25b09c0 ("KVM: x86: Mask LVTPC when handling a PMI"), but is still
> a bug.
>
> Note, the "Track emulated counter events instead of previous counter" fix
> breaks the PMU KVM-Unit-Test due to a long-standing "bug" in perf[*]. If need
> be, it's trivial to fudge around the shortcomings in the KUT code, I just
> haven't carved out time to push things along.
>
> [*] https://lore.kernel.org/all/20231107183605.409588-1-seanjc@xxxxxxxxxx
>
> The following changes since commit e9e60c82fe391d04db55a91c733df4a017c28b2f:
>
> selftests/kvm: fix compilation on non-x86_64 platforms (2023-11-21 11:58:25 -0500)
>
> are available in the Git repository at:
>
> https://github.com/kvm-x86/linux.git tags/kvm-x86-pmu-6.8
>
> for you to fetch changes up to fd89499a5151d197ba30f7b801f6d8f4646cf446:
>
> KVM: x86/pmu: Track emulated counter events instead of previous counter (2023-11-30 12:52:55 -0800)
Pulled, thanks.
Paolo
> ----------------------------------------------------------------
> KVM x86 PMU changes for 6.8:
>
> - Fix a variety of bugs where KVM fail to stop/reset counters and other state
> prior to refreshing the vPMU model.
>
> - Fix a double-overflow PMU bug by tracking emulated counter events using a
> dedicated field instead of snapshotting the "previous" counter. If the
> hardware PMC count triggers overflow that is recognized in the same VM-Exit
> that KVM manually bumps an event count, KVM would pend PMIs for both the
> hardware-triggered overflow and for KVM-triggered overflow.
>
> ----------------------------------------------------------------
> Sean Christopherson (6):
> KVM: x86/pmu: Move PMU reset logic to common x86 code
> KVM: x86/pmu: Reset the PMU, i.e. stop counters, before refreshing
> KVM: x86/pmu: Stop calling kvm_pmu_reset() at RESET (it's redundant)
> KVM: x86/pmu: Remove manual clearing of fields in kvm_pmu_init()
> KVM: x86/pmu: Update sample period in pmc_write_counter()
> KVM: x86/pmu: Track emulated counter events instead of previous counter
>
> arch/x86/include/asm/kvm-x86-pmu-ops.h | 2 +-
> arch/x86/include/asm/kvm_host.h | 17 +++-
> arch/x86/kvm/pmu.c | 140 +++++++++++++++++++++++++++------
> arch/x86/kvm/pmu.h | 47 +----------
> arch/x86/kvm/svm/pmu.c | 17 ----
> arch/x86/kvm/vmx/pmu_intel.c | 22 ------
> arch/x86/kvm/x86.c | 1 -
> 7 files changed, 137 insertions(+), 109 deletions(-)
>
