KVM: VMX: Drop guest CPUID check for VMXE in vmx_set_cr4()

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: 5e1746d ("KVM: nVMX: Allow setting the VMXE bit in CR4") Reported-by: Stas Sergeev <[email protected]> Signed-off-by: Sean Christopherson <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>
dabrace · Nov 15, 2020 · d3a9e41 · d3a9e41
1 parent c887c9b
commit d3a9e41
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
@@ -3129,9 +3129,10 @@ 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;
 	}