[v4,0/6] KVM: x86: Hyper-V invariant TSC control feature

Message

Vitaly Kuznetsov Sept. 22, 2022, 2:36 p.m. UTC

Changes since v3:
- Use cpuid_entry_override() for the newly introduces CPUID_8000_0007_EDX
  leaf in __do_cpuid_func(). [Sean]
- Add comments and reshuffle check in kvm_hv_invtsc_suppressed() [Sean]

Original description:

Normally, genuine Hyper-V doesn't expose architectural invariant TSC
(CPUID.80000007H:EDX[8]) to its guests by default. A special PV MSR
(HV_X64_MSR_TSC_INVARIANT_CONTROL, 0x40000118) and corresponding CPUID
feature bit (CPUID.0x40000003.EAX[15]) were introduced. When bit 0 of the
PV MSR is set, invariant TSC bit starts to show up in CPUID. When the 
feature is exposed to Hyper-V guests, reenlightenment becomes unneeded.

Note: strictly speaking, KVM doesn't have to have the feature as exposing
raw invariant TSC bit (CPUID.80000007H:EDX[8]) also seems to work for
modern Windows versions. The feature is, however, tiny and straitforward
and gives additional flexibility so why not.

Vitaly Kuznetsov (6):
  x86/hyperv: Add HV_INVARIANT_TSC_EXPOSED define
  KVM: x86: Introduce CPUID_8000_0007_EDX 'scattered' leaf
  KVM: x86: Hyper-V invariant TSC control
  KVM: selftests: Rename 'msr->availble' to 'msr->fault_exepected' in
    hyperv_features test
  KVM: selftests: Convert hyperv_features test to using
    KVM_X86_CPU_FEATURE()
  KVM: selftests: Test Hyper-V invariant TSC control

 arch/x86/include/asm/hyperv-tlfs.h            |   3 +
 arch/x86/include/asm/kvm_host.h               |   1 +
 arch/x86/kernel/cpu/mshyperv.c                |   2 +-
 arch/x86/kvm/cpuid.c                          |  11 +-
 arch/x86/kvm/hyperv.c                         |  19 ++
 arch/x86/kvm/hyperv.h                         |  27 +++
 arch/x86/kvm/reverse_cpuid.h                  |   9 +-
 arch/x86/kvm/x86.c                            |   4 +-
 .../selftests/kvm/include/x86_64/hyperv.h     | 144 ++++++++----
 .../selftests/kvm/include/x86_64/processor.h  |   1 +
 .../selftests/kvm/x86_64/hyperv_features.c    | 212 +++++++++++-------
 11 files changed, 295 insertions(+), 138 deletions(-)