Hello Thomas, I'm inlining the diff you posted so I can comment on it directly before it's officially posted to the list.
On Wed, 27 May 2026 08:56:33 +0200 Thomas Zimmermann <[email protected]> wrote: > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c > b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 545933c7f712..07e117673124 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -554,21 +554,6 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, > struct drm_device *dev, > } > EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create); > > -static void drm_gem_shmem_record_mkwrite(struct vm_fault *vmf) > -{ > - struct vm_area_struct *vma = vmf->vma; > - struct drm_gem_object *obj = vma->vm_private_data; > - struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); > - loff_t num_pages = obj->size >> PAGE_SHIFT; > - pgoff_t page_offset = vmf->pgoff - vma->vm_pgoff; /* page offset within > VMA */ > - > - if (drm_WARN_ON(obj->dev, !shmem->pages || page_offset >= num_pages)) > - return; > - > - file_update_time(vma->vm_file); > - folio_mark_dirty(page_folio(shmem->pages[page_offset])); > -} > - > static vm_fault_t try_insert_pfn(struct vm_fault *vmf, unsigned int order, > unsigned long pfn) > { > @@ -581,23 +566,16 @@ static vm_fault_t try_insert_pfn(struct vm_fault *vmf, > unsigned int order, > > if (aligned && > folio_test_pmd_mappable(page_folio(pfn_to_page(pfn)))) { > - vm_fault_t ret; > - > pfn &= PMD_MASK >> PAGE_SHIFT; > > - /* Unlike PTEs which are automatically upgraded to > + /* > + * Unlike PTEs which are automatically upgraded to > * writeable entries, the PMD upgrades go through > * .huge_fault(). Make sure we pass the "write" info > * along in that case. > - * This also means we have to record the write fault > - * here, instead of in .pfn_mkwrite(). > */ > - ret = vmf_insert_pfn_pmd(vmf, pfn, > - vmf->flags & FAULT_FLAG_WRITE); > - if (ret == VM_FAULT_NOPAGE && (vmf->flags & > FAULT_FLAG_WRITE)) > - drm_gem_shmem_record_mkwrite(vmf); > - > - return ret; > + return vmf_insert_pfn_pmd(vmf, pfn, > + vmf->flags & > FAULT_FLAG_WRITE); I believe we can go back to return vmf_insert_pfn_pmd(vmf, pfn, false); if the mappings are no longer adjusted to catch write accesses. > } > #endif > } > @@ -635,8 +613,15 @@ static vm_fault_t drm_gem_shmem_any_fault(struct > vm_fault *vmf, unsigned int ord > pfn = page_to_pfn(page); > > ret = try_insert_pfn(vmf, order, pfn); > - if (ret == VM_FAULT_NOPAGE) > + if (ret == VM_FAULT_NOPAGE) { > folio_mark_accessed(folio); > + /* > + * Always record write access to the buffer. The natural > + * place would be pfn_mkwrite, but this breaks KVM. > + */ > + file_update_time(vma->vm_file); > + folio_mark_dirty(folio); We can be a bit smarter here: /* * Always record write access to the buffer if the * mapping is writeable. The natural place would be * pfn_mkwrite, but this breaks KVM. */ if (vma->vm_flags & VM_WRITE) { file_update_time(vma->vm_file); folio_mark_dirty(folio); } > + } The rest looks good to me. Regards, Boris
