On 8/27/2026 3:30 PM, Matthew Brost wrote:
On Thu, Aug 27, 2026 at 03:14:45PM +0800, Honglei Huang wrote:
Make the HMM fault step of drm_gpusvm_get_pages(), including its -EBUSY
retry loop, into a helper drm_gpusvm_hmm_fault(). The existing logic of
the public drm_gpusvm_get_pages() is not changed, only relocated, so
there is no functional change. Keeping the retry loop in common code
also means drivers never have to open-code their own fault/retry loop.
A single fault can later be shared by several drm_gpusvm_pages instances
that mirror the same CPU range. This prepares get_pages() to split the
shared MM-level fault from the per-device DMA mapping. No functional
change intended.
I think you might want to just wait on this until Sunday for this
series. I think this patch [1] is in the core MM tree so when drm-tip
moves to 7.3.rc1, Sunday, we will have a version of this helper to core
MM used in gpusvm.
Got it, will wait until Sunday. Thanks for the information.
Regards,
Honglei
Matt
[1]
https://lore.freedesktop.org/nouveau/[email protected]/T/#m68f663ce3e802d7692363c70e6364569134cd6c7
Suggested-by: Matthew Brost <[email protected]>
Signed-off-by: Honglei Huang <[email protected]>
---
drivers/gpu/drm/drm_gpusvm.c | 67 ++++++++++++++++++++++++------------
1 file changed, 45 insertions(+), 22 deletions(-)
diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index fcfe635bc195..507ef6f0a60e 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -1442,6 +1442,50 @@ static bool drm_gpusvm_pages_valid_unlocked(struct
drm_gpusvm *gpusvm,
return pages_valid;
}
+/**
+ * drm_gpusvm_hmm_fault() - Run the shared HMM fault for a CPU range
+ * @gpusvm: Pointer to the GPU SVM structure
+ * @mm: The mm corresponding to the CPU range
+ * @hmm_range: The hmm_range to fault.
+ * @pfns: The pfn array to populate (size @npages)
+ * @timeout: jiffies deadline for the -EBUSY retry loop
+ *
+ * Fault the CPU pages of the range into @pfns. This is the MM level step.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int drm_gpusvm_hmm_fault(struct drm_gpusvm *gpusvm,
+ struct mm_struct *mm,
+ struct hmm_range *hmm_range,
+ unsigned long *pfns,
+ unsigned long timeout)
+{
+ int err;
+
+ if (!mmget_not_zero(mm))
+ return -EFAULT;
+
+ 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(hmm_range->notifier);
+ continue;
+ }
+ break;
+ }
+ mmput(mm);
+
+ return err;
+}
+
/**
* drm_gpusvm_get_pages() - Get pages and populate GPU SVM pages struct
* @gpusvm: Pointer to the GPU SVM structure
@@ -1503,28 +1547,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
if (!pfns)
return -ENOMEM;
- if (!mmget_not_zero(mm)) {
- err = -EFAULT;
- goto err_free;
- }
-
- 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;
- }
- mmput(mm);
+ err = drm_gpusvm_hmm_fault(gpusvm, mm, &hmm_range, pfns, timeout);
if (err)
goto err_free;
--
2.34.1
