diff mbox series

[v3,3/3] swiotlb: Honour dma_alloc_coherent() alignment in swiotlb_alloc()

Message ID 20240205190127.20685-4-will@kernel.org
State New
Headers
Series Fix double allocation in swiotlb_alloc() |

Commit Message

Will Deacon Feb. 5, 2024, 7:01 p.m. UTC 
  core-api/dma-api-howto.rst states the following properties of
dma_alloc_coherent():

  | The CPU virtual address and the DMA address are both guaranteed to
  | be aligned to the smallest PAGE_SIZE order which is greater than or
  | equal to the requested size.

However, swiotlb_alloc() passes zero for the 'alloc_align_mask'
parameter of swiotlb_find_slots() and so this property is not upheld.
Instead, allocations larger than a page are aligned to PAGE_SIZE,

Calculate the mask corresponding to the page order suitable for holding
the allocation and pass that to swiotlb_find_slots().

Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Petr Tesarik <petr.tesarik1@huawei-partners.com>
Cc: Dexuan Cui <decui@microsoft.com>
Fixes: e81e99bacc9f ("swiotlb: Support aligned swiotlb buffers")
Signed-off-by: Will Deacon <will@kernel.org>
---
 kernel/dma/swiotlb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Petr Tesařík Feb. 19, 2024, 12:41 p.m. UTC | #1 
On Mon,  5 Feb 2024 19:01:27 +0000
Will Deacon <will@kernel.org> wrote:

> core-api/dma-api-howto.rst states the following properties of
> dma_alloc_coherent():
> 
>   | The CPU virtual address and the DMA address are both guaranteed to
>   | be aligned to the smallest PAGE_SIZE order which is greater than or
>   | equal to the requested size.
> 
> However, swiotlb_alloc() passes zero for the 'alloc_align_mask'
> parameter of swiotlb_find_slots() and so this property is not upheld.
> Instead, allocations larger than a page are aligned to PAGE_SIZE,
> 
> Calculate the mask corresponding to the page order suitable for holding
> the allocation and pass that to swiotlb_find_slots().
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Petr Tesarik <petr.tesarik1@huawei-partners.com>
> Cc: Dexuan Cui <decui@microsoft.com>
> Fixes: e81e99bacc9f ("swiotlb: Support aligned swiotlb buffers")
> Signed-off-by: Will Deacon <will@kernel.org>

Reviewed-by: Petr Tesarik <petr.tesarik1@huawei-partners.com>

Petr T

> ---
>  kernel/dma/swiotlb.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index adbb3143238b..283eea33dd22 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -1633,12 +1633,14 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
>  	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
>  	struct io_tlb_pool *pool;
>  	phys_addr_t tlb_addr;
> +	unsigned int align;
>  	int index;
>  
>  	if (!mem)
>  		return NULL;
>  
> -	index = swiotlb_find_slots(dev, 0, size, 0, &pool);
> +	align = (1 << (get_order(size) + PAGE_SHIFT)) - 1;
> +	index = swiotlb_find_slots(dev, 0, size, align, &pool);
>  	if (index == -1)
>  		return NULL;
>
diff mbox series

Patch

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index adbb3143238b..283eea33dd22 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1633,12 +1633,14 @@  struct page *swiotlb_alloc(struct device *dev, size_t size)
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
 	struct io_tlb_pool *pool;
 	phys_addr_t tlb_addr;
+	unsigned int align;
 	int index;
 
 	if (!mem)
 		return NULL;
 
-	index = swiotlb_find_slots(dev, 0, size, 0, &pool);
+	align = (1 << (get_order(size) + PAGE_SHIFT)) - 1;
+	index = swiotlb_find_slots(dev, 0, size, align, &pool);
 	if (index == -1)
 		return NULL;