linux-kernel - [GIT PULL] KVM: x86: PMU changes for 6.8

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Message-ID: <20240104193303.3175844-7-seanjc@google.com>
Date: Thu,  4 Jan 2024 11:33:01 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Sean Christopherson <seanjc@...gle.com>
Subject: [GIT PULL] KVM: x86: PMU changes for 6.8

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@google.com

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)

----------------------------------------------------------------
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(-)