KVM: MMU: add tracepoint for check_mmio_spte

It is useful for debug mmio spte invalidation

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.c

@@ -283,8 +283,13 @@ static bool set_mmio_spte(struct kvm *kvm, u64 *sptep, gfn_t gfn,
 
 static bool check_mmio_spte(struct kvm *kvm, u64 spte)
 {
-	return likely(get_mmio_spte_generation(spte) ==
-			kvm_current_mmio_generation(kvm));
+	unsigned int kvm_gen, spte_gen;
+
+	kvm_gen = kvm_current_mmio_generation(kvm);
+	spte_gen = get_mmio_spte_generation(spte);
+
+	trace_check_mmio_spte(spte, kvm_gen, spte_gen);
+	return likely(kvm_gen == spte_gen);
 }
 
 static inline u64 rsvd_bits(int s, int e)

arch/x86/kvm/mmutrace.h

@@ -298,6 +298,30 @@ TRACE_EVENT(
 		  __entry->mmu_valid_gen, __entry->mmu_used_pages
 	)
 );
+
+
+TRACE_EVENT(
+	check_mmio_spte,
+	TP_PROTO(u64 spte, unsigned int kvm_gen, unsigned int spte_gen),
+	TP_ARGS(spte, kvm_gen, spte_gen),
+
+	TP_STRUCT__entry(
+		__field(unsigned int, kvm_gen)
+		__field(unsigned int, spte_gen)
+		__field(u64, spte)
+	),
+
+	TP_fast_assign(
+		__entry->kvm_gen = kvm_gen;
+		__entry->spte_gen = spte_gen;
+		__entry->spte = spte;
+	),
+
+	TP_printk("spte %llx kvm_gen %x spte-gen %x valid %d", __entry->spte,
+		  __entry->kvm_gen, __entry->spte_gen,
+		  __entry->kvm_gen == __entry->spte_gen
+	)
+);
 #endif /* _TRACE_KVMMMU_H */
 
 #undef TRACE_INCLUDE_PATH