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| author |   Sean Christopherson <seanjc@google.com> | 2022-06-08 22:45:12 +0000 |
|---|---|---|
| committer |   Paolo Bonzini <pbonzini@redhat.com> | 2022-06-20 11:50:42 -0400 |
| commit | bfbcc81bb82cbbad8bf4e40cea274f42b50674e2 (patch) | |
| tree | 644d8901c84e9720c22a819b706773951201e31c /Documentation/virt/kvm | |
| parent | KVM: x86: Ignore benign host writes to "unsupported" F15H_PERF_CTL MSRs (diff) | |
| download | linux-dev-bfbcc81bb82cbbad8bf4e40cea274f42b50674e2.tar.xz linux-dev-bfbcc81bb82cbbad8bf4e40cea274f42b50674e2.zip | |
KVM: x86: Add a quirk for KVM's "MONITOR/MWAIT are NOPs!" behavior
Add a quirk for KVM's behavior of emulating intercepted MONITOR/MWAIT
instructions a NOPs regardless of whether or not they are supported in
guest CPUID. KVM's current behavior was likely motiviated by a certain
fruity operating system that expects MONITOR/MWAIT to be supported
unconditionally and blindly executes MONITOR/MWAIT without first checking
CPUID. And because KVM does NOT advertise MONITOR/MWAIT to userspace,
that's effectively the default setup for any VMM that regurgitates
KVM_GET_SUPPORTED_CPUID to KVM_SET_CPUID2.
Note, this quirk interacts with KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT. The
behavior is actually desirable, as userspace VMMs that want to
unconditionally hide MONITOR/MWAIT from the guest can leave the
MISC_ENABLE quirk enabled.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220608224516.3788274-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt/kvm')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 84c486ce6279..320cb04f7bd9 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -7522,6 +7522,19 @@ The valid bits in cap.args[0] are: hypercall instructions. Executing the incorrect hypercall instruction will generate a #UD within the guest. + +KVM_X86_QUIRK_MWAIT_NEVER_FAULTS By default, KVM emulates MONITOR/MWAIT (if + they are intercepted) as NOPs regardless of + whether or not MONITOR/MWAIT are supported + according to guest CPUID. When this quirk + is disabled and KVM_X86_DISABLE_EXITS_MWAIT + is not set (MONITOR/MWAIT are intercepted), + KVM will inject a #UD on MONITOR/MWAIT if + they're unsupported per guest CPUID. Note, + KVM will modify MONITOR/MWAIT support in + guest CPUID on writes to MISC_ENABLE if + KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT is + disabled. =================================== ============================================ 7.32 KVM_CAP_MAX_VCPU_ID |