+ drm-gpusvm-use-hmm_range_fault_unlocked_timeout-for-range-faults.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: drm/gpusvm: use hmm_range_fault_unlocked_timeout() for range faults
has been added to the -mm mm-unstable branch.  Its filename is
     drm-gpusvm-use-hmm_range_fault_unlocked_timeout-for-range-faults.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/drm-gpusvm-use-hmm_range_fault_unlocked_timeout-for-range-faults.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Stanislav Kinsburskii <skinsburskii@gmail.com>
Subject: drm/gpusvm: use hmm_range_fault_unlocked_timeout() for range faults
Date: Wed, 15 Jul 2026 11:16:52 -0700

Several GPU SVM paths take mmap_read_lock() only to call hmm_range_fault()
and open-code mmu interval sequence setup before each HMM walk.  They also
retry -EBUSY until HMM_RANGE_DEFAULT_TIMEOUT expires.

Use hmm_range_fault_unlocked_timeout() for those faults.  The HMM helper
now owns mmap_lock acquisition and refreshes range->notifier_seq for its
internal retries, while GPU SVM keeps its existing driver-lock validation
with mmu_interval_read_retry() after a successful fault.

Pass HMM_RANGE_DEFAULT_TIMEOUT as the helper retry budget for each HMM
fault attempt.  This scopes the timeout to repeated HMM notifier retries
while preserving the outer retry loops that restart when the interval is
invalidated before GPU SVM updates or consumes the mapping state.

Leave drm_gpusvm_check_pages() on hmm_range_fault() because that path is
called with the mmap lock already held by its caller.

Link: https://lore.kernel.org/178413941236.1155966.14485211391150425997.stgit@skinsburskii
Signed-off-by: Stanislav Kinsburskii <skinsburskii@gmail.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <kees@kernel.org>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lizhi Hou <lizhi.hou@amd.com>
Cc: Long Li <longli@microsoft.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Lyude <lyude@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oded Gabbay <ogabbay@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Zimemrmann <tzimmermann@suse.de>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/gpu/drm/drm_gpusvm.c |   61 +++------------------------------
 1 file changed, 7 insertions(+), 54 deletions(-)

--- a/drivers/gpu/drm/drm_gpusvm.c~drm-gpusvm-use-hmm_range_fault_unlocked_timeout-for-range-faults
+++ a/drivers/gpu/drm/drm_gpusvm.c
@@ -773,8 +773,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_s
 		.end = end,
 		.dev_private_owner = dev_private_owner,
 	};
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	enum drm_gpusvm_scan_result state = DRM_GPUSVM_SCAN_UNPOPULATED, new_state;
 	unsigned long *pfns;
 	unsigned long npages = npages_in_range(start, end);
@@ -788,22 +787,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_s
 	hmm_range.hmm_pfns = pfns;
 
 retry:
-	hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
-	mmap_read_lock(range->gpusvm->mm);
-
-	while (true) {
-		err = hmm_range_fault(&hmm_range);
-		if (err == -EBUSY) {
-			if (time_after(jiffies, timeout))
-				break;
-
-			hmm_range.notifier_seq =
-				mmu_interval_read_begin(notifier);
-			continue;
-		}
-		break;
-	}
-	mmap_read_unlock(range->gpusvm->mm);
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 	if (err)
 		goto err_free;
 
@@ -1406,8 +1390,7 @@ int drm_gpusvm_get_pages(struct drm_gpus
 		.dev_private_owner = ctx->device_private_page_owner,
 	};
 	void *zdd;
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	unsigned long i, j;
 	unsigned long npages = npages_in_range(pages_start, pages_end);
 	unsigned long num_dma_mapped;
@@ -1422,9 +1405,6 @@ int drm_gpusvm_get_pages(struct drm_gpus
 	struct dma_iova_state *state = &svm_pages->state;
 
 retry:
-	if (time_after(jiffies, timeout))
-		return -EBUSY;
-
 	hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
 	if (drm_gpusvm_pages_valid_unlocked(gpusvm, svm_pages))
 		goto set_seqno;
@@ -1439,21 +1419,7 @@ retry:
 	}
 
 	hmm_range.hmm_pfns = pfns;
-	while (true) {
-		mmap_read_lock(mm);
-		err = hmm_range_fault(&hmm_range);
-		mmap_read_unlock(mm);
-
-		if (err == -EBUSY) {
-			if (time_after(jiffies, timeout))
-				break;
-
-			hmm_range.notifier_seq =
-				mmu_interval_read_begin(notifier);
-			continue;
-		}
-		break;
-	}
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 	mmput(mm);
 	if (err)
 		goto err_free;
@@ -1720,8 +1686,7 @@ int drm_gpusvm_range_evict(struct drm_gp
 		.end = drm_gpusvm_range_end(range),
 		.dev_private_owner = NULL,
 	};
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	unsigned long *pfns;
 	unsigned long npages = npages_in_range(drm_gpusvm_range_start(range),
 					       drm_gpusvm_range_end(range));
@@ -1736,24 +1701,12 @@ int drm_gpusvm_range_evict(struct drm_gp
 		return -ENOMEM;
 
 	hmm_range.hmm_pfns = pfns;
-	while (!time_after(jiffies, timeout)) {
-		hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
-		if (time_after(jiffies, timeout)) {
-			err = -ETIME;
-			break;
-		}
-
-		mmap_read_lock(mm);
-		err = hmm_range_fault(&hmm_range);
-		mmap_read_unlock(mm);
-		if (err != -EBUSY)
-			break;
-	}
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 
 	kvfree(pfns);
 	mmput(mm);
 
-	return err;
+	return err == -EBUSY ? -ETIME : err;
 }
 EXPORT_SYMBOL_GPL(drm_gpusvm_range_evict);
 
_

Patches currently in -mm which might be from skinsburskii@gmail.com are

lib-test_hmm-use-device-devt-for-coherent-device-range-selection.patch
mm-hmm-move-page-fault-handling-out-of-walk-callbacks.patch
mm-hmm-add-hmm_range_fault_unlocked_timeout-for-mmap-lock-drop-support.patch
selftests-mm-add-hmm-test-for-mmap-lock-dropping-faults.patch
mshv-use-hmm_range_fault_unlocked_timeout-for-region-faults.patch
drm-nouveau-use-hmm_range_fault_unlocked_timeout-for-svm-faults.patch
rdma-umem-use-hmm_range_fault_unlocked_timeout-for-odp-faults.patch
accel-amdxdna-use-hmm_range_fault_unlocked_timeout-for-range-population.patch
drm-gpusvm-use-hmm_range_fault_unlocked_timeout-for-range-faults.patch