On Tue, 7 Oct 2025 16:01:47 +0100 Adrián Larumbe <[email protected]> wrote:
> In the MMU's page fault ISR for a heap object, determine whether the > faulting address belongs to a 2MiB block that was already mapped by > checking its corresponding sgt in the Panfrost BO. > > Also avoid retrieving pages from the shmem file if last one in the block > was already present, as this means all of them had already been fetched. > > This is done in preparation for a future commit in which the MMU mapping > helper might fail, but the page array is left populated, so this cannot > be used as a check for an early bail-out. > > Signed-off-by: Adrián Larumbe <[email protected]> > --- > drivers/gpu/drm/panfrost/panfrost_mmu.c | 41 +++++++++++++++---------- > 1 file changed, 24 insertions(+), 17 deletions(-) > > diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c > b/drivers/gpu/drm/panfrost/panfrost_mmu.c > index cf272b167feb..72864d0d478e 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c > +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c > @@ -600,32 +600,39 @@ static int panfrost_mmu_map_fault_addr(struct > panfrost_device *pfdev, int as, > refcount_set(&bo->base.pages_use_count, 1); > } else { > pages = bo->base.pages; > - if (pages[page_offset]) { > - /* Pages are already mapped, bail out. */ > - goto out; > - } > + } > + > + sgt = &bo->sgts[page_offset / (SZ_2M / PAGE_SIZE)]; > + if (sgt->sgl) { > + /* Pages are already mapped, bail out. */ > + goto out; > } > > mapping = bo->base.base.filp->f_mapping; > mapping_set_unevictable(mapping); > > - for (i = page_offset; i < page_offset + NUM_FAULT_PAGES; i++) { > - /* Can happen if the last fault only partially filled this > - * section of the pages array before failing. In that case > - * we skip already filled pages. > + if (!pages[page_offset + NUM_FAULT_PAGES - 1]) { > + /* Pages are retrieved sequentially, so if the very last > + * one in the subset we want to map is already assigned, then > + * there's no need to further iterate. > */ I don't think we care about optimizing the page range walk in the unlikely case of a double fault on the same section, so I'd just keep the existing loop unchanged. > - if (pages[i]) > - continue; > - > - pages[i] = shmem_read_mapping_page(mapping, i); > - if (IS_ERR(pages[i])) { > - ret = PTR_ERR(pages[i]); > - pages[i] = NULL; > - goto err_unlock; > + for (i = page_offset; i < page_offset + NUM_FAULT_PAGES; i++) { > + /* Can happen if the last fault only partially filled > this > + * section of the pages array before failing. In that > case > + * we skip already filled pages. > + */ > + if (pages[i]) > + continue; > + > + pages[i] = shmem_read_mapping_page(mapping, i); > + if (IS_ERR(pages[i])) { > + ret = PTR_ERR(pages[i]); > + pages[i] = NULL; > + goto err_unlock; > + } > } > } > > - sgt = &bo->sgts[page_offset / (SZ_2M / PAGE_SIZE)]; > ret = sg_alloc_table_from_pages(sgt, pages + page_offset, > NUM_FAULT_PAGES, 0, SZ_2M, GFP_KERNEL); > if (ret)
