KVM: MMU: fix apf prefault if nested guest is enabled

If apf is generated in L2 guest and is completed in L1 guest, it will
prefault this apf in L1 guest's mmu context.
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -600,6 +600,7 @@ struct kvm_x86_ops {
 struct kvm_arch_async_pf {
 	u32 token;
 	gfn_t gfn;
+	bool direct_map;
 };
 
 extern struct kvm_x86_ops *kvm_x86_ops;

arch/x86/kvm/mmu.c

@@ -2609,6 +2609,7 @@ static int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn)
 	struct kvm_arch_async_pf arch;
 	arch.token = (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id;
 	arch.gfn = gfn;
+	arch.direct_map = vcpu->arch.mmu.direct_map;
 
 	return kvm_setup_async_pf(vcpu, gva, gfn, &arch);
 }

arch/x86/kvm/x86.c

@@ -6168,7 +6168,8 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
 {
 	int r;
 
-	if (!vcpu->arch.mmu.direct_map || is_error_page(work->page))
+	if (!vcpu->arch.mmu.direct_map || !work->arch.direct_map ||
+	      is_error_page(work->page))
 		return;
 
 	r = kvm_mmu_reload(vcpu);