Re: [PATCH V1 1/2] drm/gpusvm: add drm_gpusvm_pages unmapped and retry helpers

[Matthew Brost]

On Mon, Nov 09, 2026 at 11:53:37AM -0800, Lizhi Hou wrote:
> Hi Matthew,
> 
> 
> How do we converge on this?  Both 2 patches are reviewed, is it good to
> merge them to drm-misc-next?
> 

I also gave an RB, feel free to merge or if you need help merging, let
me know and I can merge them.

Matt

> Honglei, Thanks a lot for reviewing the code.
> 
> 
> Lizhi
> 
> On 11/9/26 00:56, Huang, Honglei1 wrote:
> > AMD General
> > 
> > Reviewed-by: Honglei Huang <honghuan@xxxxxxx>
> > 
> > -----Original Message-----
> > From: Lizhi Hou <lizhi.hou@xxxxxxx>
> > Sent: Saturday, November 7, 2026 2:42 AM
> > To: ogabbay@xxxxxxxxxx; quic_jhugo@xxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Limonciello, Mario <Mario.Limonciello@xxxxxxx>; karol.wachowski@xxxxxxxxxxxxxxx; Zhen, Max <Max.Zhen@xxxxxxx>; thomas.hellstrom@xxxxxxxxxxxxxxx; himal.prasad.ghimiray@xxxxxxxxx; Huang, Honglei1 <Honglei1.Huang@xxxxxxx>
> > Cc: Matthew Brost <matthew.brost@xxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Santan, Sonal <sonal.santan@xxxxxxx>; Hou, Lizhi <lizhi.hou@xxxxxxx>
> > Subject: [PATCH V1 1/2] drm/gpusvm: add drm_gpusvm_pages unmapped and retry helpers
> > 
> > From: Matthew Brost <matthew.brost@xxxxxxxxx>
> > 
> > Drivers which only use the drm_gpusvm_pages API (no drm_gpusvm_range) have no way to mark pages unmapped from their MMU notifier, as
> > drm_gpusvm_range_set_unmapped() requires a range. They also have to open code the mmu_interval_read_retry() check on the recorded notifier_seq to commit pages faulted with &drm_gpusvm_ctx.no_dma_map.
> > 
> > Split the pages part of drm_gpusvm_range_set_unmapped() into drm_gpusvm_pages_set_unmapped(), and add drm_gpusvm_pages_read_retry() which performs the commit side check with a lockdep assert on the notifier lock.
> > 
> > Assisted-by: LLM
> > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> > Signed-off-by: Lizhi Hou <lizhi.hou@xxxxxxx>
> > ---
> >   drivers/gpu/drm/drm_gpusvm.c | 49 +++++++++++++++++++++++++-----------
> >   include/drm/drm_gpusvm.h     | 29 +++++++++++++++++++++
> >   2 files changed, 64 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c index 03dbe304e4b8f..63a26919f59db 100644
> > --- a/drivers/gpu/drm/drm_gpusvm.c
> > +++ b/drivers/gpu/drm/drm_gpusvm.c
> > @@ -1761,9 +1761,8 @@ static int drm_gpusvm_dma_map_pages(struct drm_gpusvm *gpusvm,
> >    *
> >    * With &drm_gpusvm_ctx.no_dma_map no mapping state is recorded, so
> >    * drm_gpusvm_pages_valid() never returns true and success is only a snapshot:
> > - * the caller must recheck mmu_interval_read_retry() against the recorded
> > - * &drm_gpusvm_pages.notifier_seq under the notifier lock, and hold it until
> > - * its work is visible to invalidation.
> > + * the caller must recheck drm_gpusvm_pages_read_retry() under the
> > + notifier
> > + * lock, and hold it until its work is visible to invalidation.
> >    *
> >    * Return: 0 on success, negative error code on failure.
> >    */
> > @@ -2021,6 +2020,38 @@ bool drm_gpusvm_has_mapping(struct drm_gpusvm *gpusvm, unsigned long start,  }  EXPORT_SYMBOL_GPL(drm_gpusvm_has_mapping);
> > 
> > +/**
> > + * drm_gpusvm_pages_set_unmapped() - Mark GPU SVM pages as unmapped
> > + * @gpusvm: Pointer to the GPU SVM structure.
> > + * @pages: Pointer to the GPU SVM pages structure(s).
> > + * @pages_count: Number of GPU SVM pages structure(s) passed in.
> > + *
> > + * Mark @pages as unmapped, after which drm_gpusvm_get_pages() fails
> > +with
> > + * -EFAULT for them. Intended to be called from the driver's MMU
> > +notifier on
> > + * MMU_NOTIFY_UNMAP, and usable without a &drm_gpusvm_range by drivers
> > +that
> > + * only use the drm_gpusvm_pages API. The caller must hold the notifier
> > +lock
> > + * in write mode.
> > + */
> > +void drm_gpusvm_pages_set_unmapped(struct drm_gpusvm *gpusvm,
> > +                                  struct drm_gpusvm_pages *pages,
> > +                                  unsigned int pages_count)
> > +{
> > +       unsigned int i;
> > +
> > +       lockdep_assert_held_write(&gpusvm->notifier_lock);
> > +
> > +       for (i = 0; i < pages_count; ++i) {
> > +               struct drm_gpusvm_pages_flags flags = {
> > +                       .__flags = pages[i].flags.__flags,
> > +               };
> > +
> > +               flags.unmapped = true;
> > +               /* WRITE_ONCE pairs with READ_ONCE for opportunistic checks */
> > +               WRITE_ONCE(pages[i].flags.__flags, flags.__flags);
> > +       }
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_pages_set_unmapped);
> > +
> >   /**
> >    * drm_gpusvm_range_set_unmapped() - Mark a GPU SVM range as unmapped
> >    * @range: Pointer to the GPU SVM range structure.
> > @@ -2039,20 +2070,10 @@ void drm_gpusvm_range_set_unmapped(struct drm_gpusvm_range *range,
> >          struct drm_gpusvm_range_flags range_flags = {
> >                  .__flags = range->flags.__flags,
> >          };
> > -       unsigned int i;
> > 
> > -       lockdep_assert_held_write(&range->gpusvm->notifier_lock);
> > +       drm_gpusvm_pages_set_unmapped(range->gpusvm, pages, pages_count);
> > 
> >          range_flags.unmapped = true;
> > -       for (i = 0; i < pages_count; ++i) {
> > -               struct drm_gpusvm_pages_flags flags = {
> > -                       .__flags = pages[i].flags.__flags,
> > -               };
> > -
> > -               flags.unmapped = true;
> > -               /* WRITE_ONCE pairs with READ_ONCE for opportunistic checks */
> > -               WRITE_ONCE(pages[i].flags.__flags, flags.__flags);
> > -       }
> >          if (drm_gpusvm_range_start(range) < mmu_range->start ||
> >              drm_gpusvm_range_end(range) > mmu_range->end)
> >                  range_flags.partial_unmap = true;
> > diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h index 4d31c6bba7455..b43432af56377 100644
> > --- a/include/drm/drm_gpusvm.h
> > +++ b/include/drm/drm_gpusvm.h
> > @@ -349,6 +349,10 @@ void drm_gpusvm_range_set_unmapped(struct drm_gpusvm_range *range,
> >                                     unsigned int pages_count,
> >                                     const struct mmu_notifier_range *mmu_range);
> > 
> > +void drm_gpusvm_pages_set_unmapped(struct drm_gpusvm *gpusvm,
> > +                                  struct drm_gpusvm_pages *pages,
> > +                                  unsigned int pages_count);
> > +
> >   int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
> >                           struct drm_gpusvm_pages *svm_pages,
> >                           unsigned int num_pages,
> > @@ -383,6 +387,31 @@ static inline void drm_gpusvm_init_pages(struct drm_gpusvm_pages *svm_pages,
> >          svm_pages->notifier_seq = LONG_MAX;
> >   }
> > 
> > +/**
> > + * drm_gpusvm_pages_read_retry() - Check whether GPU SVM pages went
> > +stale
> > + * @gpusvm: Pointer to the GPU SVM structure.
> > + * @svm_pages: Pointer to the drm_gpusvm_pages.
> > + * @notifier: The notifier passed to drm_gpusvm_get_pages() for @svm_pages.
> > + *
> > + * Check whether @notifier was invalidated since the last successful
> > + * drm_gpusvm_get_pages() for @svm_pages. This is the commit side check
> > +for
> > + * pages faulted with &drm_gpusvm_ctx.no_dma_map, where no mapping
> > +state is
> > + * tracked. Pages that were never faulted always report as stale. The
> > +caller
> > + * must hold the notifier lock and keep holding it until its use of the
> > +pages
> > + * is visible to the invalidation path.
> > + *
> > + * Return: True if the pages must be faulted again, false otherwise.
> > + */
> > +static inline bool
> > +drm_gpusvm_pages_read_retry(struct drm_gpusvm *gpusvm,
> > +                           struct drm_gpusvm_pages *svm_pages,
> > +                           struct mmu_interval_notifier *notifier) {
> > +       lockdep_assert_held(&gpusvm->notifier_lock);
> > +
> > +       return mmu_interval_read_retry(notifier, svm_pages->notifier_seq); }
> > +
> >   /**
> >    * drm_gpusvm_pages_first_dma() - Resolve the device address array
> >    * @svm_pages: Pointer to the drm_gpusvm_pages.
> > 
> > base-commit: d2a8cee91bfa8616f713c7c8f539a81e8e3554ea
> > --
> > 2.34.1
> >