KVM: nVMX: Pull exit_reason from vcpu_vmx in nested_vmx_reflect_vmexit()

Grab the exit reason from the vcpu struct in nested_vmx_reflect_vmexit()
instead of having the exit reason explicitly passed from the caller.
This fixes a discrepancy between VM-Fail and VM-Exit handling, as the
VM-Fail case is already handled by checking vcpu_vmx, e.g. the exit
reason previously passed on the stack is bogus if vmx->fail is set.

Not taking the exit reason on the stack also avoids having to document
that nested_vmx_reflect_vmexit() requires the full exit reason, as
opposed to just the basic exit reason, which is not at all obvious since
the only usages of the full exit reason are for tracing and way down in
prepare_vmcs12() where it's propagated to vmcs12.

No functional change intended.
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200415175519.14230-8-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -5826,9 +5826,10 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, u32 exit_reason)
  * Conditionally reflect a VM-Exit into L1.  Returns %true if the VM-Exit was
  * reflected into L1.
  */
-bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason)
+bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	u32 exit_reason = vmx->exit_reason;
 	u32 exit_intr_info, exit_qual;
 
 	WARN_ON_ONCE(vmx->nested.nested_run_pending);

arch/x86/kvm/vmx/nested.h

@@ -25,7 +25,7 @@ void nested_vmx_set_vmcs_shadowing_bitmap(void);
 void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu);
 enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 						     bool from_vmentry);
-bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason);
+bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu);
 void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
 		       u32 exit_intr_info, unsigned long exit_qualification);
 void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu);

arch/x86/kvm/vmx/vmx.c

@@ -5905,7 +5905,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
 		 */
 		nested_mark_vmcs12_pages_dirty(vcpu);
 
-		if (nested_vmx_reflect_vmexit(vcpu, exit_reason))
+		if (nested_vmx_reflect_vmexit(vcpu))
 			return 1;
 	}