KVM: MMU: trace fast page fault

To see what happen on this path and help us to optimize it

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 8637bff..28c8fbc 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2776,6 +2776,8 @@
 	 */
 	ret = fast_pf_fix_direct_spte(vcpu, iterator.sptep, spte);
 exit:
+	trace_fast_page_fault(vcpu, gva, error_code, iterator.sptep,
+			      spte, ret);
 	walk_shadow_page_lockless_end(vcpu);
 
 	return ret;