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Message-Id: <20240131122543.14791-4-will@kernel.org>
Date: Wed, 31 Jan 2024 12:25:43 +0000
From: Will Deacon <will@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: kernel-team@...roid.com,
Will Deacon <will@...nel.org>,
iommu@...ts.linux.dev,
Christoph Hellwig <hch@....de>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>,
Petr Tesarik <petr.tesarik1@...wei-partners.com>,
Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v2 3/3] swiotlb: Honour dma_alloc_coherent() alignment in swiotlb_alloc()
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@....de>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Petr Tesarik <petr.tesarik1@...wei-partners.com>
Cc: Dexuan Cui <decui@...rosoft.com>
Signed-off-by: Will Deacon <will@...nel.org>
---
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 4485f216e620..8ec37006ac70 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1632,12 +1632,14 @@ 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;
--
2.43.0.429.g432eaa2c6b-goog
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