Re: [PATCH rc 4/5] iommupt: Check for missing PAGE_SIZE in the pgsize_bitmap

[Samiullah Khawaja <skhawaja@google.com>]

On Tue, May 12, 2026 at 01:46:16PM -0300, Jason Gunthorpe wrote:
>Sashiko pointed out that the driver could drop PAGE_SIZE from the
>pgsize_bitmap. That is technically allowed but nothing does it, and
>such an iommu_domain would not be used with the DMA API today.
>
>Still, it is against the design and it is trivial to fix up. Lift
>the PT_WARN_ON to the if branch and just skip the fast path.
>
>Fixes: dcd6a011a8d5 ("iommupt: Add map_pages op")
>Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
>---
> drivers/iommu/generic_pt/iommu_pt.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/iommu/generic_pt/iommu_pt.h b/drivers/iommu/generic_pt/iommu_pt.h
>index 19b6daf88f2ab1..4877b05291c9d4 100644
>--- a/drivers/iommu/generic_pt/iommu_pt.h
>+++ b/drivers/iommu/generic_pt/iommu_pt.h
>@@ -920,8 +920,8 @@ static int NS(map_range)(struct pt_iommu *iommu_table, dma_addr_t iova,
> 		return ret;
>
> 	/* Calculate target page size and level for the leaves */
>-	if (pt_has_system_page_size(common) && len == PAGE_SIZE) {
>-		PT_WARN_ON(!(pgsize_bitmap & PAGE_SIZE));
>+	if (pt_has_system_page_size(common) && len == PAGE_SIZE &&
>+		likely(pgsize_bitmap & PAGE_SIZE)) {
> 		if (log2_mod(iova | paddr, PAGE_SHIFT))
> 			return -ENXIO;
> 		map.leaf_pgsize_lg2 = PAGE_SHIFT;
>-- 
>2.43.0
>

Reviewed-by: Samiullah Khawaja <skhawaja@google.com>