KVM: MMU: cache mmio info on page fault path

If the page fault is caused by mmio, we can cache the mmio info, later, we do
not need to walk guest page table and quickly know it is a mmio fault while we
emulate the mmio instruction

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -424,6 +424,11 @@ struct kvm_vcpu_arch {
 	u64 mcg_ctl;
 	u64 *mce_banks;
 
+	/* Cache MMIO info */
+	u64 mmio_gva;
+	unsigned access;
+	gfn_t mmio_gfn;
+
 	/* used for guest single stepping over the given code position */
 	unsigned long singlestep_rip;