KVM: x86/mmu: Handle KVM bookkeeping in page-track APIs, not callers

Get/put references to KVM when a page-track notifier is (un)registered
instead of relying on the caller to do so.  Forcing the caller to do the
bookkeeping is unnecessary and adds one more thing for users to get
wrong, e.g. see commit 9ed1fdee9ee3 ("drm/i915/gvt: Get reference to KVM
iff attachment to VM is successful").

Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Link: https://lore.kernel.org/r/20230729013535.1070024-29-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
index 4afab697e21ca8e1c46b65e3583b236ea85e227b..3d040741044b4142ce4c7c2f79608ac18b409c69 100644 (file)
--- a/arch/x86/include/asm/kvm_page_track.h
+++ b/arch/x86/include/asm/kvm_page_track.h
@@ -44,12 +44,11 @@ struct kvm_page_track_notifier_node {
                                    struct kvm_page_track_notifier_node *node);
 };
 
-void
-kvm_page_track_register_notifier(struct kvm *kvm,
-                                struct kvm_page_track_notifier_node *n);
-void
-kvm_page_track_unregister_notifier(struct kvm *kvm,
-                                  struct kvm_page_track_notifier_node *n);
+int kvm_page_track_register_notifier(struct kvm *kvm,
+                                    struct kvm_page_track_notifier_node *n);
+void kvm_page_track_unregister_notifier(struct kvm *kvm,
+                                       struct kvm_page_track_notifier_node *n);
+
 int kvm_write_track_add_gfn(struct kvm *kvm, gfn_t gfn);
 int kvm_write_track_remove_gfn(struct kvm *kvm, gfn_t gfn);
 #else

diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index c9ab8b587d25f93f72074c8a02bdaeb40a327f8f..c87da11f3a049b75e2dc6cae714b37e868666252 100644 (file)
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -157,17 +157,22 @@ int kvm_page_track_init(struct kvm *kvm)
  * register the notifier so that event interception for the tracked guest
  * pages can be received.
  */
-void
-kvm_page_track_register_notifier(struct kvm *kvm,
-                                struct kvm_page_track_notifier_node *n)
+int kvm_page_track_register_notifier(struct kvm *kvm,
+                                    struct kvm_page_track_notifier_node *n)
 {
        struct kvm_page_track_notifier_head *head;
 
+       if (!kvm || kvm->mm != current->mm)
+               return -ESRCH;
+
+       kvm_get_kvm(kvm);
+
        head = &kvm->arch.track_notifier_head;
 
        write_lock(&kvm->mmu_lock);
        hlist_add_head_rcu(&n->node, &head->track_notifier_list);
        write_unlock(&kvm->mmu_lock);
+       return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_page_track_register_notifier);
 
@@ -175,9 +180,8 @@ EXPORT_SYMBOL_GPL(kvm_page_track_register_notifier);
  * stop receiving the event interception. It is the opposed operation of
  * kvm_page_track_register_notifier().
  */
-void
-kvm_page_track_unregister_notifier(struct kvm *kvm,
-                                  struct kvm_page_track_notifier_node *n)
+void kvm_page_track_unregister_notifier(struct kvm *kvm,
+                                       struct kvm_page_track_notifier_node *n)
 {
        struct kvm_page_track_notifier_head *head;
 
@@ -187,6 +191,8 @@ kvm_page_track_unregister_notifier(struct kvm *kvm,
        hlist_del_rcu(&n->node);
        write_unlock(&kvm->mmu_lock);
        synchronize_srcu(&head->track_srcu);
+
+       kvm_put_kvm(kvm);
 }
 EXPORT_SYMBOL_GPL(kvm_page_track_unregister_notifier);
 

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 21342a93e4184c716342230633050e6114cc822e..eb50997dd369cbc1ac917ee6704466748a551bf5 100644 (file)
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -654,21 +654,19 @@ out:
 static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
 {
        struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
-
-       if (!vgpu->vfio_device.kvm ||
-           vgpu->vfio_device.kvm->mm != current->mm) {
-               gvt_vgpu_err("KVM is required to use Intel vGPU\n");
-               return -ESRCH;
-       }
+       int ret;
 
        if (__kvmgt_vgpu_exist(vgpu))
                return -EEXIST;
 
        vgpu->track_node.track_write = kvmgt_page_track_write;
        vgpu->track_node.track_remove_region = kvmgt_page_track_remove_region;
-       kvm_get_kvm(vgpu->vfio_device.kvm);
-       kvm_page_track_register_notifier(vgpu->vfio_device.kvm,
-                                        &vgpu->track_node);
+       ret = kvm_page_track_register_notifier(vgpu->vfio_device.kvm,
+                                              &vgpu->track_node);
+       if (ret) {
+               gvt_vgpu_err("KVM is required to use Intel vGPU\n");
+               return ret;
+       }
 
        set_bit(INTEL_VGPU_STATUS_ATTACHED, vgpu->status);
 
@@ -703,7 +701,6 @@ static void intel_vgpu_close_device(struct vfio_device *vfio_dev)
 
        kvm_page_track_unregister_notifier(vgpu->vfio_device.kvm,
                                           &vgpu->track_node);
-       kvm_put_kvm(vgpu->vfio_device.kvm);
 
        kvmgt_protect_table_destroy(vgpu);
        gvt_cache_destroy(vgpu);