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 4afab69..3d04074 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 c9ab8b5..c87da11 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 21342a9..eb50997 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);