Commit 7e0548525abd for kernel

commit 7e0548525abd2bff9694e016b6a469ccd2d5a053
Author: Robin Murphy <robin.murphy@arm.com>
Date:   Wed Apr 8 15:40:57 2026 +0100

    iommu: Ensure .iotlb_sync is called correctly

    Many drivers have no reason to use the iotlb_gather mechanism, but do
    still depend on .iotlb_sync being called to properly complete an unmap.
    Since the core code is now relying on the gather to detect when there
    is legitimately something to sync, it should also take care of encoding
    a successful unmap when the driver does not touch the gather itself.

    Fixes: 90c5def10bea ("iommu: Do not call drivers for empty gathers")
    Reported-by: Jon Hunter <jonathanh@nvidia.com>
    Closes: https://lore.kernel.org/r/8800a38b-8515-4bbe-af15-0dae81274bf7@nvidia.com
    Signed-off-by: Robin Murphy <robin.murphy@arm.com>
    Tested-by: Jon Hunter <jonathanh@nvidia.com>
    Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
    Tested-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
    Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 50718ab810a4..ee83850c7060 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2717,6 +2717,12 @@ static size_t __iommu_unmap(struct iommu_domain *domain,

 		pr_debug("unmapped: iova 0x%lx size 0x%zx\n",
 			 iova, unmapped_page);
+		/*
+		 * If the driver itself isn't using the gather, make sure
+		 * it looks non-empty so iotlb_sync will still be called.
+		 */
+		if (iotlb_gather->start >= iotlb_gather->end)
+			iommu_iotlb_gather_add_range(iotlb_gather, iova, size);

 		iova += unmapped_page;
 		unmapped += unmapped_page;