KVM: Trace exception injection

Often an exception can help point out where things start to go wrong.

Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/trace.h

@@ -219,6 +219,38 @@ TRACE_EVENT(kvm_inj_virq,
 	TP_printk("irq %u", __entry->irq)
 );
 
+#define EXS(x) { x##_VECTOR, "#" #x }
+
+#define kvm_trace_sym_exc						\
+	EXS(DE), EXS(DB), EXS(BP), EXS(OF), EXS(BR), EXS(UD), EXS(NM),	\
+	EXS(DF), EXS(TS), EXS(NP), EXS(SS), EXS(GP), EXS(PF),		\
+	EXS(MF), EXS(MC)
+
+/*
+ * Tracepoint for kvm interrupt injection:
+ */
+TRACE_EVENT(kvm_inj_exception,
+	TP_PROTO(unsigned exception, bool has_error, unsigned error_code),
+	TP_ARGS(exception, has_error, error_code),
+
+	TP_STRUCT__entry(
+		__field(	u8,	exception	)
+		__field(	u8,	has_error	)
+		__field(	u32,	error_code	)
+	),
+
+	TP_fast_assign(
+		__entry->exception	= exception;
+		__entry->has_error	= has_error;
+		__entry->error_code	= error_code;
+	),
+
+	TP_printk("%s (0x%x)",
+		  __print_symbolic(__entry->exception, kvm_trace_sym_exc),
+		  /* FIXME: don't print error_code if not present */
+		  __entry->has_error ? __entry->error_code : 0)
+);
+
 /*
  * Tracepoint for page fault.
  */

arch/x86/kvm/x86.c

@@ -4237,6 +4237,9 @@ static void inject_pending_event(struct kvm_vcpu *vcpu)
 {
 	/* try to reinject previous events if any */
 	if (vcpu->arch.exception.pending) {
+		trace_kvm_inj_exception(vcpu->arch.exception.nr,
+					vcpu->arch.exception.has_error_code,
+					vcpu->arch.exception.error_code);
 		kvm_x86_ops->queue_exception(vcpu, vcpu->arch.exception.nr,
 					  vcpu->arch.exception.has_error_code,
 					  vcpu->arch.exception.error_code);