linux-kernel - [PATCH v4 0/3] KVM: x86: Provide a capability to disable APERF/MPERF read intercepts

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Message-ID: <20250530185239.2335185-1-jmattson@google.com>
Date: Fri, 30 May 2025 11:52:22 -0700
From: Jim Mattson <jmattson@...gle.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v4 0/3] KVM: x86: Provide a capability to disable APERF/MPERF
 read intercepts

Allow a guest to read IA32_APERF and IA32_MPERF, so that it can
determine the effective frequency multiplier for the physical LPU.

Commit b51700632e0e ("KVM: X86: Provide a capability to disable cstate
msr read intercepts") allowed the userspace VMM to grant a guest read
access to four core C-state residency MSRs. Do the same for IA32_APERF
and IA32_MPERF.

While this isn't sufficient to claim support for
CPUID.6:ECX.APERFMPERF[bit 0], it may suffice in a sufficiently
restricted environment (i.e. vCPUs pinned to LPUs, no TSC multiplier,
and no suspend/resume).

v1 -> v2: Add {IA32_APERF,IA32_MPERF} to vmx_possible_passthrough_msrs[]
v2 -> v3: Add a selftest
v3 -> v4: Collect all disabled_exit flags in a u64 [Sean]
          Improve documentation [Sean]
	  Add pin_task_to_one_cpu() to kvm selftests library [Sean]


Jim Mattson (3):
  KVM: x86: Replace growing set of *_in_guest bools with a u64
  KVM: x86: Provide a capability to disable APERF/MPERF read intercepts
  KVM: selftests: Test behavior of KVM_X86_DISABLE_EXITS_APERFMPERF

 Documentation/virt/kvm/api.rst                |  23 +++
 arch/x86/include/asm/kvm_host.h               |   5 +-
 arch/x86/kvm/svm/svm.c                        |   9 +-
 arch/x86/kvm/svm/svm.h                        |   2 +-
 arch/x86/kvm/vmx/vmx.c                        |   8 +-
 arch/x86/kvm/vmx/vmx.h                        |   2 +-
 arch/x86/kvm/x86.c                            |  16 ++-
 arch/x86/kvm/x86.h                            |  18 ++-
 include/uapi/linux/kvm.h                      |   1 +
 tools/include/uapi/linux/kvm.h                |   1 +
 tools/testing/selftests/kvm/Makefile.kvm      |   1 +
 .../testing/selftests/kvm/include/kvm_util.h  |   2 +
 tools/testing/selftests/kvm/lib/kvm_util.c    |  17 +++
 .../selftests/kvm/x86/aperfmperf_test.c       | 132 ++++++++++++++++++
 14 files changed, 220 insertions(+), 17 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86/aperfmperf_test.c

-- 
2.49.0.1204.g71687c7c1d-goog