linux-kernel - [PATCH 0/2] KVM: nVMX: Fix another case where KVM overrides VMX MSRs

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Message-ID: <20221110005706.1064832-1-seanjc@google.com>
Date:   Thu, 10 Nov 2022 00:57:04 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yu Zhang <yu.c.zhang@...ux.intel.com>
Subject: [PATCH 0/2] KVM: nVMX: Fix another case where KVM overrides VMX MSRs

Fix another case where KVM overrides the VMX MSRs (well, just the one MSR)
during KVM_SET_CPUID.  Similar to somewhat recent reverts

  8805875aa473 ("Revert "KVM: nVMX: Do not expose MPX VMX controls when guest MPX disabled"")
  9389d5774aca ("Revert "KVM: nVMX: Expose load IA32_PERF_GLOBAL_CTRL VM-{Entry,Exit} control"")

undo misguided KVM behavior where KVM overrides allowed-1 settings in the
secondary execution controls in response to changes to the guest's CPUID
model.  To avoid breaking userspace that doesn't take ownership of the
VMX MSRs, go hands off if and only if userpace sets the MSR in question

Sean Christopherson (2):
  KVM: nVMX: Don't muck with allowed sec exec controls on CPUID changes
  KVM: selftests: Test KVM's handling of VMX's sec exec MSR on
    KVM_SET_CPUID

 arch/x86/kvm/vmx/capabilities.h               |  1 +
 arch/x86/kvm/vmx/nested.c                     |  3 +
 arch/x86/kvm/vmx/vmx.c                        |  2 +-
 .../selftests/kvm/include/x86_64/processor.h  |  1 +
 .../selftests/kvm/include/x86_64/vmx.h        |  4 +-
 .../selftests/kvm/x86_64/vmx_msrs_test.c      | 92 +++++++++++++++++++
 6 files changed, 100 insertions(+), 3 deletions(-)


base-commit: d663b8a285986072428a6a145e5994bc275df994
-- 
2.38.1.431.g37b22c650d-goog