linux-kernel - [PATCH v5 0/5] KVM: x86: Provide a cap to disable APERF/MPERF read intercepts

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Message-ID: <20250626001225.744268-1-seanjc@google.com>
Date: Wed, 25 Jun 2025 17:12:20 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, 
	Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v5 0/5] KVM: x86: Provide a cap to disable APERF/MPERF read intercepts

arm64 folks, y'all got pulled in because of selftests changes.  I deliberately
put that patch at the end of the series so that it can be discarded/ignored
without interfering with the x86 stuff.


Jim's series to 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).

v5:
 - Rebase on top of the MSR interception rework.
 - Support passthrough to L2 on VMX (it was there somewhat unintentionally
   for SVM).
 - Expand the selftest to cover the nested case.
 - Sanity check that the MSRs are inaccesible in the selftest.
 - Add selftests patches to expand the task=>CPU pinning APIs.
 - OR-in the new disabled exits in one batch.

v4:
 - https://lore.kernel.org/all/20250530185239.2335185-1-jmattson@google.com
 - Collect all disabled_exit flags in a u64 [Sean]
 - Improve documentation [Sean]
 - Add pin_task_to_one_cpu() to kvm selftests library [Sean]

v3:
 - https://lore.kernel.org/all/20250321221444.2449974-1-jmattson@google.com
 - Add a selftest

v2:
 - https://lore.kernel.org/all/20250314180117.740591-1-jmattson@google.com
 - Add {IA32_APERF,IA32_MPERF} to vmx_possible_passthrough_msrs[]

v1:
 - https://lore.kernel.org/all/20250225004708.1001320-1-jmattson@google.com

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

Sean Christopherson (2):
  KVM: selftests: Expand set of APIs for pinning tasks to a single CPU
  KVM: selftests: Convert arch_timer tests to common helpers to pin task

 Documentation/virt/kvm/api.rst                |  23 ++
 arch/x86/include/asm/kvm_host.h               |   5 +-
 arch/x86/kvm/svm/nested.c                     |   4 +-
 arch/x86/kvm/svm/svm.c                        |   7 +-
 arch/x86/kvm/vmx/nested.c                     |   6 +
 arch/x86/kvm/vmx/vmx.c                        |   6 +-
 arch/x86/kvm/x86.c                            |  15 +-
 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 +
 tools/testing/selftests/kvm/arch_timer.c      |   7 +-
 .../kvm/arm64/arch_timer_edge_cases.c         |  23 +-
 .../testing/selftests/kvm/include/kvm_util.h  |  31 ++-
 tools/testing/selftests/kvm/lib/kvm_util.c    |  15 +-
 tools/testing/selftests/kvm/lib/memstress.c   |   2 +-
 .../selftests/kvm/x86/aperfmperf_test.c       | 213 ++++++++++++++++++
 17 files changed, 321 insertions(+), 57 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86/aperfmperf_test.c


base-commit: 7ee45fdd644b138e7a213c6936474161b28d0e1a
-- 
2.50.0.727.gbf7dc18ff4-goog