On Thu, Sep 17, 2026 at 02:33:46PM +0200, Boris Brezillon wrote: > With the recent changes to iova_mapped_as_huge_page(), the check for > huge-page mapping of sparse BOs is actually simple: > > - for a sparse mapping, we know the BO offset any VA in this regions is > va & (SZ_2M - 1) > - the VA we're searching the BO offset for is the 2M-aligned > aligned_va value > > This guarantees that the BO offset to check is always zero in that case. > > This is simple enough to let the code check if page 0 is a huge page > and save the unmap+map dance when the dummy BO is not backed by a > a huge page. So let's do that and kill the comment that says it's too > complicated. > > Signed-off-by: Boris Brezillon <[email protected]>
Reviewed-by: Liviu Dudau <[email protected]> Best regards, Liviu > --- > drivers/gpu/drm/panthor/panthor_mmu.c | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c > b/drivers/gpu/drm/panthor/panthor_mmu.c > index d2897099763e..01564d250adf 100644 > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > @@ -2337,18 +2337,18 @@ iova_mapped_as_huge_page(struct drm_gpuva *mapping, > u64 va) > > return false; > } else { > - const struct page *pg = bo->backing.pages[bo_offset >> > PAGE_SHIFT]; > struct panthor_vma *vma = container_of(mapping, struct > panthor_vma, base); > bool is_sparse = vma->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE; > + const struct page *pg; > > - /* If the unmapped VMA stands for a sparse mapping, always > - * assume the backing storage is a THP, since the overhead of > - * unmapping 2MiB worth of 4KiB pages and remapping some of > - * them is offset by the logic of working out whether it's > - * the opposite case right below. > + /* BO offset on a sparse mapping is chosen so that 2M-aligned > + * VAs point to the start of the BO. Since aligned_va (the > + * address we check huge-page against) is 2M-aligned, the BO > + * offset is guaranteed to be zero. > + * Check panthor_fix_sparse_map_offset() for more details. > */ > if (is_sparse) > - return true; > + bo_offset = 0; > > /* In case of shmem backing, we know we can only have a huge > * mapping if the bo_offset is 2M aligned, meaning we can skip > @@ -2357,6 +2357,7 @@ iova_mapped_as_huge_page(struct drm_gpuva *mapping, u64 > va) > if (!IS_ALIGNED(bo_offset, SZ_2M)) > return false; > > + pg = bo->backing.pages[bo_offset >> PAGE_SHIFT]; > return folio_size(page_folio(pg)) >= SZ_2M; > } > } > > -- > 2.55.0 > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯
