KVM: Trace failed msr reads and writes

Record failed msrs reads and writes, and the fact that they failed as well.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/svm.c

@@ -2177,9 +2177,10 @@ static int rdmsr_interception(struct vcpu_svm *svm)
 	u32 ecx = svm->vcpu.arch.regs[VCPU_REGS_RCX];
 	u64 data;
 
-	if (svm_get_msr(&svm->vcpu, ecx, &data))
+	if (svm_get_msr(&svm->vcpu, ecx, &data)) {
+		trace_kvm_msr_read_ex(ecx);
 		kvm_inject_gp(&svm->vcpu, 0);
-	else {
+	} else {
 		trace_kvm_msr_read(ecx, data);
 
 		svm->vcpu.arch.regs[VCPU_REGS_RAX] = data & 0xffffffff;
@@ -2271,13 +2272,15 @@ static int wrmsr_interception(struct vcpu_svm *svm)
 	u64 data = (svm->vcpu.arch.regs[VCPU_REGS_RAX] & -1u)
 		| ((u64)(svm->vcpu.arch.regs[VCPU_REGS_RDX] & -1u) << 32);
 
-	trace_kvm_msr_write(ecx, data);
 
 	svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
-	if (svm_set_msr(&svm->vcpu, ecx, data))
+	if (svm_set_msr(&svm->vcpu, ecx, data)) {
+		trace_kvm_msr_write_ex(ecx, data);
 		kvm_inject_gp(&svm->vcpu, 0);
-	else
+	} else {
+		trace_kvm_msr_write(ecx, data);
 		skip_emulated_instruction(&svm->vcpu);
+	}
 	return 1;
 }
 

arch/x86/kvm/trace.h

@@ -246,28 +246,33 @@ TRACE_EVENT(kvm_page_fault,
  * Tracepoint for guest MSR access.
  */
 TRACE_EVENT(kvm_msr,
-	TP_PROTO(unsigned write, u32 ecx, u64 data),
-	TP_ARGS(write, ecx, data),
+	TP_PROTO(unsigned write, u32 ecx, u64 data, bool exception),
+	TP_ARGS(write, ecx, data, exception),
 
 	TP_STRUCT__entry(
 		__field(	unsigned,	write		)
 		__field(	u32,		ecx		)
 		__field(	u64,		data		)
+		__field(	u8,		exception	)
 	),
 
 	TP_fast_assign(
 		__entry->write		= write;
 		__entry->ecx		= ecx;
 		__entry->data		= data;
+		__entry->exception	= exception;
 	),
 
-	TP_printk("msr_%s %x = 0x%llx",
+	TP_printk("msr_%s %x = 0x%llx%s",
 		  __entry->write ? "write" : "read",
-		  __entry->ecx, __entry->data)
+		  __entry->ecx, __entry->data,
+		  __entry->exception ? " (#GP)" : "")
 );
 
-#define trace_kvm_msr_read(ecx, data)		trace_kvm_msr(0, ecx, data)
-#define trace_kvm_msr_write(ecx, data)		trace_kvm_msr(1, ecx, data)
+#define trace_kvm_msr_read(ecx, data)      trace_kvm_msr(0, ecx, data, false)
+#define trace_kvm_msr_write(ecx, data)     trace_kvm_msr(1, ecx, data, false)
+#define trace_kvm_msr_read_ex(ecx)         trace_kvm_msr(0, ecx, 0, true)
+#define trace_kvm_msr_write_ex(ecx, data)  trace_kvm_msr(1, ecx, data, true)
 
 /*
  * Tracepoint for guest CR access.

arch/x86/kvm/vmx.c

@@ -3158,6 +3158,7 @@ static int handle_rdmsr(struct kvm_vcpu *vcpu)
 	u64 data;
 
 	if (vmx_get_msr(vcpu, ecx, &data)) {
+		trace_kvm_msr_read_ex(ecx);
 		kvm_inject_gp(vcpu, 0);
 		return 1;
 	}
@@ -3177,13 +3178,13 @@ static int handle_wrmsr(struct kvm_vcpu *vcpu)
 	u64 data = (vcpu->arch.regs[VCPU_REGS_RAX] & -1u)
 		| ((u64)(vcpu->arch.regs[VCPU_REGS_RDX] & -1u) << 32);
 
-	trace_kvm_msr_write(ecx, data);
-
 	if (vmx_set_msr(vcpu, ecx, data) != 0) {
+		trace_kvm_msr_write_ex(ecx, data);
 		kvm_inject_gp(vcpu, 0);
 		return 1;
 	}
 
+	trace_kvm_msr_write(ecx, data);
 	skip_emulated_instruction(vcpu);
 	return 1;
 }