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    Subject[PATCH 5.10 499/545] KVM: VMX: Drop guest CPUID check for VMXE in vmx_set_cr4()
    Date
    From: Sean Christopherson <sean.j.christopherson@intel.com>

    [ Upstream commit d3a9e4146a6f79f19430bca3f2a4d6ebaaffe36b ]

    Drop vmx_set_cr4()'s somewhat hidden guest_cpuid_has() check on VMXE now
    that common x86 handles the check by incorporating VMXE into the CR4
    reserved bits, i.e. in cr4_guest_rsvd_bits. This fixes a bug where KVM
    incorrectly rejects KVM_SET_SREGS with CR4.VMXE=1 if it's executed
    before KVM_SET_CPUID{,2}.

    Fixes: 5e1746d6205d ("KVM: nVMX: Allow setting the VMXE bit in CR4")
    Reported-by: Stas Sergeev <stsp@users.sourceforge.net>
    Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Message-Id: <20201007014417.29276-2-sean.j.christopherson@intel.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kvm/vmx/vmx.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    index 9b520da3f748..1b75847d8a49 100644
    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -3217,9 +3217,10 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
    * must first be able to turn on cr4.VMXE (see handle_vmon()).
    * So basically the check on whether to allow nested VMX
    * is here. We operate under the default treatment of SMM,
    - * so VMX cannot be enabled under SMM.
    + * so VMX cannot be enabled under SMM. Note, guest CPUID is
    + * intentionally ignored, it's handled by cr4_guest_rsvd_bits.
    */
    - if (!nested_vmx_allowed(vcpu) || is_smm(vcpu))
    + if (!nested || is_smm(vcpu))
    return 1;
    }

    --
    2.35.1


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