# Re: \[PATCH v6 15/20\] iommu/dma: Check atomic pool allocation result directly

- From: Petr Tesarik \<hidden\>
- Date: 2026-06-09 13:27:01 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2026/06/17109423
- Thread: https://ratatoskr.run/linux-iommu/2026/06/17087574/t.md

```text
On Thu,  4 Jun 2026 14:09:54 +0530
"Aneesh Kumar K.V (Arm)" [ref] wrote:

> The non-blocking, non-coherent allocation path uses dma_alloc_from_pool(),
> which returns the allocated page and fills cpu_addr only on success.
> 
> Do not rely on cpu_addr to detect allocation failure in this path. Check
> the returned page directly before using it for the IOMMU mapping.
> 
> Fixes: 9420139f516d ("dma-pool: fix coherent pool allocations for IOMMU mappings")
> Tested-by: Michael Kelley <redacted>
> Tested-by: Mostafa Saleh <smostafa@google.com>
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>

Reviewed-by: Petr Tesarik <redacted>

Petr T

> ---
>  drivers/iommu/dma-iommu.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 725c7adb0a8d..52c599f4472c 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1671,13 +1671,16 @@ void *iommu_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
>  	}
>  
>  	if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
> -	    !gfpflags_allow_blocking(gfp) && !coherent)
> +	    !gfpflags_allow_blocking(gfp) && !coherent) {
>  		page = dma_alloc_from_pool(dev, PAGE_ALIGN(size), &cpu_addr,
>  					   gfp, attrs, NULL);
> -	else
> +		if (!page)
> +			return NULL;
> +	} else {
>  		cpu_addr = iommu_dma_alloc_pages(dev, size, &page, gfp, attrs);
> -	if (!cpu_addr)
> -		return NULL;
> +		if (!cpu_addr)
> +			return NULL;
> +	}
>  
>  	*handle = __iommu_dma_map(dev, page_to_phys(page), size, ioprot,
>  			dev->coherent_dma_mask);


```