[PATCH v2 2/2] KVM: nVMX: Do eVMCS consistency check on VMFUNC controls iff they're enable

[Sean Christopherson <seanjc@google.com>]

Check that the VM-function controls are actually enabled before performing
eVMCS-specific consistency checks, as the VMFUNC controls are supposed to
be completely ignored if they're not enabled.  Per the SDM:

  If the "enable VM functions" processor-based VM-execution control is 0,
  no checks are performed on the VM-function controls.

Fixes: 3ff8a13d41b2 ("KVM: nVMX: WARN once and fail VM-Enter if eVMCS sees VMFUNC[63:32] != 0")
Fixes: a83502314ce3 ("x86/kvm/hyper-v: don't allow to turn on unsupported VMX controls for nested guests")
Cc: stable@vger.kernel.org
Reported-by: Manuel Andreas <manuel.andreas@tum.de>
Closes: https://lore.kernel.org/all/f1f39118-2e1b-476b-9a84-ef7d56412bdc@tum.de
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/hyperv.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx/hyperv.c b/arch/x86/kvm/vmx/hyperv.c
index 2b40ac32ff06..a1daf8f2ec5a 100644
--- a/arch/x86/kvm/vmx/hyperv.c
+++ b/arch/x86/kvm/vmx/hyperv.c
@@ -187,11 +187,10 @@ int nested_evmcs_check_controls(struct vmcs12 *vmcs12)
 	 * controls in bits 63:32, i.e. dropping those bits on the consistency
 	 * check is intentional.
 	 */
-	if (WARN_ON_ONCE(vmcs12->vm_function_control >> 32))
-		return -EINVAL;
-
-	if (CC(!nested_evmcs_is_valid_controls(EVMCS_VMFUNC,
-					       vmcs12->vm_function_control)))
+	if (nested_cpu_has_vmfunc(vmcs12) &&
+	    (WARN_ON_ONCE(vmcs12->vm_function_control >> 32) ||
+	     CC(!nested_evmcs_is_valid_controls(EVMCS_VMFUNC,
+						vmcs12->vm_function_control))))
 		return -EINVAL;
 
 	return 0;
-- 
2.56.0.567.gdb80ae8cd5-goog