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>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3e893cd..417f36b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -283,8 +283,13 @@
 
 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)