nouveau: use mmu_notifier directly for invalidate_range_start

There is no reason to get the invalidate_range_start() callback via an
indirection through hmm_mirror, just register a normal notifier directly.

Link: https://lore.kernel.org/r/20191112202231.3856-9-jgg@ziepe.caTested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/gpu/drm/nouveau/nouveau_svm.c

@@ -88,6 +88,7 @@ nouveau_ivmm_find(struct nouveau_svm *svm, u64 inst)
 }
 
 struct nouveau_svmm {
+	struct mmu_notifier notifier;
 	struct nouveau_vmm *vmm;
 	struct {
 		unsigned long start;
@@ -96,7 +97,6 @@ struct nouveau_svmm {
 
 	struct mutex mutex;
 
-	struct mm_struct *mm;
 	struct hmm_mirror mirror;
 };
 
@@ -251,10 +251,11 @@ nouveau_svmm_invalidate(struct nouveau_svmm *svmm, u64 start, u64 limit)
 }
 
 static int
-nouveau_svmm_sync_cpu_device_pagetables(struct hmm_mirror *mirror,
-					const struct mmu_notifier_range *update)
+nouveau_svmm_invalidate_range_start(struct mmu_notifier *mn,
+				    const struct mmu_notifier_range *update)
 {
-	struct nouveau_svmm *svmm = container_of(mirror, typeof(*svmm), mirror);
+	struct nouveau_svmm *svmm =
+		container_of(mn, struct nouveau_svmm, notifier);
 	unsigned long start = update->start;
 	unsigned long limit = update->end;
 
@@ -264,6 +265,9 @@ nouveau_svmm_sync_cpu_device_pagetables(struct hmm_mirror *mirror,
 	SVMM_DBG(svmm, "invalidate %016lx-%016lx", start, limit);
 
 	mutex_lock(&svmm->mutex);
+	if (unlikely(!svmm->vmm))
+		goto out;
+
 	if (limit > svmm->unmanaged.start && start < svmm->unmanaged.limit) {
 		if (start < svmm->unmanaged.start) {
 			nouveau_svmm_invalidate(svmm, start,
@@ -273,19 +277,31 @@ nouveau_svmm_sync_cpu_device_pagetables(struct hmm_mirror *mirror,
 	}
 
 	nouveau_svmm_invalidate(svmm, start, limit);
+
+out:
 	mutex_unlock(&svmm->mutex);
 	return 0;
 }
 
-static void
-nouveau_svmm_release(struct hmm_mirror *mirror)
+static void nouveau_svmm_free_notifier(struct mmu_notifier *mn)
+{
+	kfree(container_of(mn, struct nouveau_svmm, notifier));
+}
+
+static const struct mmu_notifier_ops nouveau_mn_ops = {
+	.invalidate_range_start = nouveau_svmm_invalidate_range_start,
+	.free_notifier = nouveau_svmm_free_notifier,
+};
+
+static int
+nouveau_svmm_sync_cpu_device_pagetables(struct hmm_mirror *mirror,
+					const struct mmu_notifier_range *update)
 {
+	return 0;
 }
 
-static const struct hmm_mirror_ops
-nouveau_svmm = {
+static const struct hmm_mirror_ops nouveau_svmm = {
 	.sync_cpu_device_pagetables = nouveau_svmm_sync_cpu_device_pagetables,
-	.release = nouveau_svmm_release,
 };
 
 void
@@ -294,7 +310,10 @@ nouveau_svmm_fini(struct nouveau_svmm **psvmm)
 	struct nouveau_svmm *svmm = *psvmm;
 	if (svmm) {
 		hmm_mirror_unregister(&svmm->mirror);
-		kfree(*psvmm);
+		mutex_lock(&svmm->mutex);
+		svmm->vmm = NULL;
+		mutex_unlock(&svmm->mutex);
+		mmu_notifier_put(&svmm->notifier);
 		*psvmm = NULL;
 	}
 }
@@ -320,7 +339,7 @@ nouveau_svmm_init(struct drm_device *dev, void *data,
 	mutex_lock(&cli->mutex);
 	if (cli->svm.cli) {
 		ret = -EBUSY;
-		goto done;
+		goto out_free;
 	}
 
 	/* Allocate a new GPU VMM that can support SVM (managed by the
@@ -335,24 +354,33 @@ nouveau_svmm_init(struct drm_device *dev, void *data,
 				.fault_replay = true,
 			    }, sizeof(struct gp100_vmm_v0), &cli->svm.vmm);
 	if (ret)
-		goto done;
+		goto out_free;
 
-	/* Enable HMM mirroring of CPU address-space to VMM. */
-	svmm->mm = get_task_mm(current);
-	down_write(&svmm->mm->mmap_sem);
+	down_write(&current->mm->mmap_sem);
 	svmm->mirror.ops = &nouveau_svmm;
-	ret = hmm_mirror_register(&svmm->mirror, svmm->mm);
-	if (ret == 0) {
-		cli->svm.svmm = svmm;
-		cli->svm.cli = cli;
-	}
-	up_write(&svmm->mm->mmap_sem);
-	mmput(svmm->mm);
+	ret = hmm_mirror_register(&svmm->mirror, current->mm);
+	if (ret)
+		goto out_mm_unlock;
 
-done:
+	svmm->notifier.ops = &nouveau_mn_ops;
+	ret = __mmu_notifier_register(&svmm->notifier, current->mm);
 	if (ret)
-		nouveau_svmm_fini(&svmm);
+		goto out_hmm_unregister;
+	/* Note, ownership of svmm transfers to mmu_notifier */
+
+	cli->svm.svmm = svmm;
+	cli->svm.cli = cli;
+	up_write(&current->mm->mmap_sem);
 	mutex_unlock(&cli->mutex);
+	return 0;
+
+out_hmm_unregister:
+	hmm_mirror_unregister(&svmm->mirror);
+out_mm_unlock:
+	up_write(&current->mm->mmap_sem);
+out_free:
+	mutex_unlock(&cli->mutex);
+	kfree(svmm);
 	return ret;
 }
 
@@ -494,12 +522,12 @@ nouveau_range_fault(struct nouveau_svmm *svmm, struct hmm_range *range)
 
 	ret = hmm_range_register(range, &svmm->mirror);
 	if (ret) {
-		up_read(&svmm->mm->mmap_sem);
+		up_read(&svmm->notifier.mm->mmap_sem);
 		return (int)ret;
 	}
 
 	if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
-		up_read(&svmm->mm->mmap_sem);
+		up_read(&svmm->notifier.mm->mmap_sem);
 		return -EBUSY;
 	}
 
@@ -507,7 +535,7 @@ nouveau_range_fault(struct nouveau_svmm *svmm, struct hmm_range *range)
 	if (ret <= 0) {
 		if (ret == 0)
 			ret = -EBUSY;
-		up_read(&svmm->mm->mmap_sem);
+		up_read(&svmm->notifier.mm->mmap_sem);
 		hmm_range_unregister(range);
 		return ret;
 	}
@@ -587,12 +615,15 @@ nouveau_svm_fault(struct nvif_notify *notify)
 	args.i.p.version = 0;
 
 	for (fi = 0; fn = fi + 1, fi < buffer->fault_nr; fi = fn) {
+		struct mm_struct *mm;
+
 		/* Cancel any faults from non-SVM channels. */
 		if (!(svmm = buffer->fault[fi]->svmm)) {
 			nouveau_svm_fault_cancel_fault(svm, buffer->fault[fi]);
 			continue;
 		}
 		SVMM_DBG(svmm, "addr %016llx", buffer->fault[fi]->addr);
+		mm = svmm->notifier.mm;
 
 		/* We try and group handling of faults within a small
 		 * window into a single update.
@@ -609,11 +640,11 @@ nouveau_svm_fault(struct nvif_notify *notify)
 		/* Intersect fault window with the CPU VMA, cancelling
 		 * the fault if the address is invalid.
 		 */
-		down_read(&svmm->mm->mmap_sem);
-		vma = find_vma_intersection(svmm->mm, start, limit);
+		down_read(&mm->mmap_sem);
+		vma = find_vma_intersection(mm, start, limit);
 		if (!vma) {
 			SVMM_ERR(svmm, "wndw %016llx-%016llx", start, limit);
-			up_read(&svmm->mm->mmap_sem);
+			up_read(&mm->mmap_sem);
 			nouveau_svm_fault_cancel_fault(svm, buffer->fault[fi]);
 			continue;
 		}
@@ -623,7 +654,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
 
 		if (buffer->fault[fi]->addr != start) {
 			SVMM_ERR(svmm, "addr %016llx", buffer->fault[fi]->addr);
-			up_read(&svmm->mm->mmap_sem);
+			up_read(&mm->mmap_sem);
 			nouveau_svm_fault_cancel_fault(svm, buffer->fault[fi]);
 			continue;
 		}
@@ -704,7 +735,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
 						NULL);
 			svmm->vmm->vmm.object.client->super = false;
 			mutex_unlock(&svmm->mutex);
-			up_read(&svmm->mm->mmap_sem);
+			up_read(&mm->mmap_sem);
 		}
 
 		/* Cancel any faults in the window whose pages didn't manage