From: David Woodhouse <dwmw@amazon.co.uk>
Date: Thu, 21 Jan 2021 11:28:42 +0000 (+0000)
Subject: KVM: x86/xen: Fix initialisation of gfn caches for Xen shared pages
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3eadbaba08f380d0b870928f19a40e9a1f6e826c;p=users%2Fdwmw2%2Flinux.git

KVM: x86/xen: Fix initialisation of gfn caches for Xen shared pages

When kvm_gfn_to_hva_cache_init() is used to cache the address of the
guest pages which KVM needs to access, it uses kvm_memslots(). For
which an RCU read lock is required. Add that around the whole of
the kvm_xen_hvm_set_attr() function.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 4bc9da9fcfb80..46111de1df53e 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -219,11 +219,14 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 {
 	struct kvm_vcpu *v;
 	int r = -ENOENT;
+	int idx = srcu_read_lock(&vcpu->kvm->srcu);
 
 	switch (data->type) {
 	case KVM_XEN_ATTR_TYPE_LONG_MODE:
-		if (!IS_ENABLED(CONFIG_64BIT) && data->u.long_mode)
-			return -EINVAL;
+		if (!IS_ENABLED(CONFIG_64BIT) && data->u.long_mode) {
+			r = -EINVAL;
+			goto out;
+		}
 
 		kvm->arch.xen.long_mode = !!data->u.long_mode;
 		r = 0;
@@ -235,8 +238,11 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 
 	case KVM_XEN_ATTR_TYPE_VCPU_INFO:
 		v = kvm_get_vcpu_by_id(kvm, data->u.vcpu_attr.vcpu_id);
-		if (!v)
-			return -EINVAL;
+		if (!v) {
+			r = -EINVAL;
+			goto out;
+		}
+
 		/* No compat necessary here. */
 		BUILD_BUG_ON(sizeof(struct vcpu_info) !=
 			     sizeof(struct compat_vcpu_info));
@@ -247,7 +253,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 					      data->u.vcpu_attr.gpa,
 					      sizeof(struct vcpu_info));
 		if (r)
-			return r;
+			goto out;
 
 		v->arch.xen.vcpu_info_set = true;
 		kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
@@ -255,14 +261,16 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 
 	case KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO:
 		v = kvm_get_vcpu_by_id(kvm, data->u.vcpu_attr.vcpu_id);
-		if (!v)
-			return -EINVAL;
+		if (!v) {
+			r = -EINVAL;
+			goto out;
+		}
 
 		r = kvm_gfn_to_hva_cache_init(kvm, &v->arch.xen.vcpu_time_info_cache,
 					      data->u.vcpu_attr.gpa,
 					      sizeof(struct pvclock_vcpu_time_info));
 		if (r)
-			return r;
+			goto out;
 
 		v->arch.xen.vcpu_time_info_set = true;
 		kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
@@ -270,14 +278,16 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 
 	case KVM_XEN_ATTR_TYPE_VCPU_RUNSTATE:
 		v = kvm_get_vcpu_by_id(kvm, data->u.vcpu_attr.vcpu_id);
-		if (!v)
-			return -EINVAL;
+		if (!v) {
+			r = -EINVAL;
+			goto out;
+		}
 
 		r = kvm_gfn_to_hva_cache_init(kvm, &v->arch.xen.runstate_cache,
 					      data->u.vcpu_attr.gpa,
 					      sizeof(struct vcpu_runstate_info));
 		if (r)
-			return r;
+			goto out;
 
 		v->arch.xen.runstate_set = true;
 		v->arch.xen.current_runstate = RUNSTATE_blocked;
@@ -285,8 +295,10 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 		break;
 
 	case KVM_XEN_ATTR_TYPE_UPCALL_VECTOR:
-		if (data->u.vector < 0x10)
-			return -EINVAL;
+		if (data->u.vector < 0x10) {
+			r = -EINVAL;
+			goto out;
+		}
 
 		kvm->arch.xen.upcall_vector = data->u.vector;
 		r = 0;
@@ -296,6 +308,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 		break;
 	}
 
+	srcu_read_unlock(&kvm->srcu, idx);
 	return r;
 }