KVM: SVM: Fix the svm vmexit code for WRMSR

In svm, exit_code for MSR writes is not EXIT_REASON_MSR_WRITE which
belongs to vmx.

According to amd manual, SVM_EXIT_MSR(7ch) is the exit_code of VMEXIT_MSR
due to RDMSR or WRMSR access to protected MSR. Additionally, the processor
indicates in the VMCB's EXITINFO1 whether a RDMSR(EXITINFO1=0) or
WRMSR(EXITINFO1=1) was intercepted.

Signed-off-by: Haiwei Li <lihaiwei@tencent.com>
Fixes: 1e9e2622a1 ("KVM: VMX: FIXED+PHYSICAL mode single target IPI fastpath", 2019-11-21)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm.c

@@ -6312,7 +6312,8 @@ static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu,
 	enum exit_fastpath_completion *exit_fastpath)
 {
 	if (!is_guest_mode(vcpu) &&
-		to_svm(vcpu)->vmcb->control.exit_code == EXIT_REASON_MSR_WRITE)
+	    to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_MSR &&
+	    to_svm(vcpu)->vmcb->control.exit_info_1)
 		*exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu);
 }