KVM: x86/xen: Add KVM_XEN_INVALID_GPA and KVM_XEN_INVALID_GFN to uapi

These are (uint64_t)-1 magic values are a userspace ABI, allowing the
shared info pages and other enlightenments to be disabled. This isn't
a Xen ABI because Xen doesn't let the guest turn these off except with
the full SHUTDOWN_soft_reset mechanism. Under KVM, the userspace VMM is
expected to handle soft reset, and tear down the kernel parts of the
enlightenments accordingly.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20221226120320.1125390-5-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/xen.c

@@ -41,7 +41,7 @@ static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
 	int ret = 0;
 	int idx = srcu_read_lock(&kvm->srcu);
 
-	if (gfn == GPA_INVALID) {
+	if (gfn == KVM_XEN_INVALID_GFN) {
 		kvm_gpc_deactivate(gpc);
 		goto out;
 	}
@@ -659,7 +659,7 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 		if (kvm->arch.xen.shinfo_cache.active)
 			data->u.shared_info.gfn = gpa_to_gfn(kvm->arch.xen.shinfo_cache.gpa);
 		else
-			data->u.shared_info.gfn = GPA_INVALID;
+			data->u.shared_info.gfn = KVM_XEN_INVALID_GFN;
 		r = 0;
 		break;
 
@@ -705,7 +705,7 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
 			     offsetof(struct compat_vcpu_info, time));
 
-		if (data->u.gpa == GPA_INVALID) {
+		if (data->u.gpa == KVM_XEN_INVALID_GPA) {
 			kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
 			r = 0;
 			break;
@@ -719,7 +719,7 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		break;
 
 	case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
-		if (data->u.gpa == GPA_INVALID) {
+		if (data->u.gpa == KVM_XEN_INVALID_GPA) {
 			kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);
 			r = 0;
 			break;
@@ -739,7 +739,7 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 			r = -EOPNOTSUPP;
 			break;
 		}
-		if (data->u.gpa == GPA_INVALID) {
+		if (data->u.gpa == KVM_XEN_INVALID_GPA) {
 			r = 0;
 		deactivate_out:
 			kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
@@ -937,7 +937,7 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		if (vcpu->arch.xen.vcpu_info_cache.active)
 			data->u.gpa = vcpu->arch.xen.vcpu_info_cache.gpa;
 		else
-			data->u.gpa = GPA_INVALID;
+			data->u.gpa = KVM_XEN_INVALID_GPA;
 		r = 0;
 		break;
 
@@ -945,7 +945,7 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		if (vcpu->arch.xen.vcpu_time_info_cache.active)
 			data->u.gpa = vcpu->arch.xen.vcpu_time_info_cache.gpa;
 		else
-			data->u.gpa = GPA_INVALID;
+			data->u.gpa = KVM_XEN_INVALID_GPA;
 		r = 0;
 		break;
 

include/uapi/linux/kvm.h

@@ -1767,6 +1767,7 @@ struct kvm_xen_hvm_attr {
 		__u8 runstate_update_flag;
 		struct {
 			__u64 gfn;
+#define KVM_XEN_INVALID_GFN ((__u64)-1)
 		} shared_info;
 		struct {
 			__u32 send_port;
@@ -1798,6 +1799,7 @@ struct kvm_xen_hvm_attr {
 	} u;
 };
 
+
 /* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO */
 #define KVM_XEN_ATTR_TYPE_LONG_MODE		0x0
 #define KVM_XEN_ATTR_TYPE_SHARED_INFO		0x1
@@ -1823,6 +1825,7 @@ struct kvm_xen_vcpu_attr {
 	__u16 pad[3];
 	union {
 		__u64 gpa;
+#define KVM_XEN_INVALID_GPA ((__u64)-1)
 		__u64 pad[8];
 		struct {
 			__u64 state;