The ultimate goal of this series is to track emulated counter events using a dedicated variable instead of trying to track the previous counter value. Tracking the previous counter value is flawed as it takes a snapshot at every emulated event, but only checks for overflow prior to VM-Enter, i.e. KVM could miss an overflow if KVM ever supports emulating event types that can occur multiple times in a single VM-Exit. And as Mingwei root caused, emulating overflow while the perf event is running can result in duplicate overflow events, e.g. if the perf event overflows between taking and checking the snapshot. This bug is largely masked now that KVM correctly sets LVT_MASK when delivering PMIs, but it's still a bug, e.g. could cause problems if there are other side effects. Patches 1-5 are (some loosely, some tightly) related fixes and cleanups to simplify the emulated counter approach implementation. The fixes are tagged for stable as usersepace could cause some weirdness around perf events, but I doubt any real world VMM is actually affected. Dapeng, I intentionally omitted your Reviewed-by from the last patch as the change from v1 isn't trivial. v2: - Collect reviews. [Dapeng] - Emulate overflow *after* pausing perf event. [Mingwei] v1: https://lore.kernel.org/all/20231023234000.2499267-1-seanjc@xxxxxxxxxx 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(-) base-commit: 45b890f7689eb0aba454fc5831d2d79763781677 -- 2.42.0.869.gea05f2083d-goog
