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SubjectRe: [PATCH v2 2/2] dma-iommu: Check that swiotlb is active before trying to use it
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On 2022-04-04 21:47, Mario Limonciello via iommu wrote:
> If the IOMMU is in use and an untrusted device is connected to an external
> facing port but the address requested isn't page aligned will cause the
> kernel to attempt to use bounce buffers.
>
> If for some reason the bounce buffers have not been allocated this is a
> problem that should be made apparent to the user.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> v1->v2:
> * Move error message into the caller
>
> drivers/iommu/dma-iommu.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 09f6e1c0f9c0..1ca85d37eeab 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -971,6 +971,11 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> void *padding_start;
> size_t padding_size, aligned_size;
>
> + if (!is_swiotlb_active(dev)) {
> + dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
> + return DMA_MAPPING_ERROR;
> + }
> +
> aligned_size = iova_align(iovad, size);
> phys = swiotlb_tbl_map_single(dev, phys, size, aligned_size,
> iova_mask(iovad), dir, attrs);

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