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 4bc9da9fcfb80d8ba4c8ecc95ba2327cc7c5ddd4..46111de1df53e043592fccf5b2d9481d2eee702c 100644 (file)
--- 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;
 }