KVM: MMU: retry #PF for softmmu

Retry #PF for softmmu only when the current vcpu has the same cr3 as the time
when #PF occurs

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

arch/x86/include/asm/kvm_host.h

@@ -593,6 +593,7 @@ struct kvm_x86_ops {
 struct kvm_arch_async_pf {
 	u32 token;
 	gfn_t gfn;
+	unsigned long cr3;
 	bool direct_map;
 };