[PATCH 5.10 499/545] KVM: VMX: Drop guest CPUID check for VMXE in vmx_set_cr4()

Greg Kroah-Hartman
2022-08-19T16:46:27Z

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