4 files changed, 29 insertions, 1 deletions
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1df95f10c903..1bab87a444d7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1263,7 +1263,7 @@ struct kvm_arch_async_pf {
 };
 
 extern u64 __read_mostly host_efer;
-
+extern bool __read_mostly allow_smaller_maxphyaddr;
 extern struct kvm_x86_ops kvm_x86_ops;
 
 #define __KVM_HAVE_ARCH_VM_ALLOC
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2371b1e40f39..783330d0e7b8 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -924,6 +924,21 @@ static __init int svm_hardware_setup(void)
 
 	svm_set_cpu_caps();
 
+	/*
+	 * It seems that on AMD processors PTE's accessed bit is
+	 * being set by the CPU hardware before the NPF vmexit.
+	 * This is not expected behaviour and our tests fail because
+	 * of it.
+	 * A workaround here is to disable support for
+	 * GUEST_MAXPHYADDR < HOST_MAXPHYADDR if NPT is enabled.
+	 * In this case userspace can know if there is support using
+	 * KVM_CAP_SMALLER_MAXPHYADDR extension and decide how to handle
+	 * it
+	 * If future AMD CPU models change the behaviour described above,
+	 * this variable can be changed accordingly
+	 */
+	allow_smaller_maxphyaddr = !npt_enabled;
+
 	return 0;
 
 err:
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 962a78c7dde5..1bb59ae5016d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8309,6 +8309,13 @@ static int __init vmx_init(void)
 #endif
 	vmx_check_vmcs12_offsets();
 
+	/*
+	 * Intel processors don't have problems with
+	 * GUEST_MAXPHYADDR < HOST_MAXPHYADDR so enable
+	 * it for VMX by default
+	 */
+	allow_smaller_maxphyaddr = true;
+
 	return 0;
 }
 module_init(vmx_init);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 35abe69aad28..95ef62922869 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -187,6 +187,9 @@ static struct kvm_shared_msrs __percpu *shared_msrs;
 u64 __read_mostly host_efer;
 EXPORT_SYMBOL_GPL(host_efer);
 
+bool __read_mostly allow_smaller_maxphyaddr;
+EXPORT_SYMBOL_GPL(allow_smaller_maxphyaddr);
+
 static u64 __read_mostly host_xss;
 u64 __read_mostly supported_xss;
 EXPORT_SYMBOL_GPL(supported_xss);
@@ -3574,6 +3577,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
 		r = kvm_x86_ops.nested_ops->enable_evmcs != NULL;
 		break;
+	case KVM_CAP_SMALLER_MAXPHYADDR:
+		r = (int) allow_smaller_maxphyaddr;
+		break;
 	default:
 		break;
 	}