From: Christoph Hellwig <hch@infradead.org>
To: David Stevens <stevensd@chromium.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org, Tom Murphy <murphyt7@tcd.ie>,
iommu@lists.linux-foundation.org
Subject: Re: [PATCH v3 1/5] dma-iommu: fix sync_sg with swiotlb
Date: Wed, 11 Aug 2021 06:57:25 +0100 [thread overview]
Message-ID: <YRNmxU9Ou2OcvBq2@infradead.org> (raw)
In-Reply-To: <20210811024247.1144246-2-stevensd@google.com>
On Wed, Aug 11, 2021 at 11:42:43AM +0900, David Stevens wrote:
> From: David Stevens <stevensd@chromium.org>
>
> The is_swiotlb_buffer function takes the physical address of the swiotlb
> buffer, not the physical address of the original buffer. The sglist
> contains the physical addresses of the original buffer, so for the
> sync_sg functions to work properly when a bounce buffer might have been
> used, we need to use iommu_iova_to_phys to look up the physical address.
> This is what sync_single does, so call that function on each sglist
> segment.
>
> The previous code mostly worked because swiotlb does the transfer on map
> and unmap. However, any callers which use DMA_ATTR_SKIP_CPU_SYNC with
> sglists or which call sync_sg would not have had anything copied to the
> bounce buffer.
>
> Fixes: 82612d66d51d ("iommu: Allow the dma-iommu api to use bounce buffers")
> Signed-off-by: David Stevens <stevensd@chromium.org>
> ---
> drivers/iommu/dma-iommu.c | 27 +++++++++++++--------------
> 1 file changed, 13 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 98ba927aee1a..54e103b989d9 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -813,14 +813,13 @@ static void iommu_dma_sync_sg_for_cpu(struct device *dev,
> if (dev_is_dma_coherent(dev) && !dev_is_untrusted(dev))
> return;
>
> + if (dev_is_untrusted(dev))
> + for_each_sg(sgl, sg, nelems, i)
> + iommu_dma_sync_single_for_cpu(dev, sg_dma_address(sg),
> + sg->length, dir);
> + else
> + for_each_sg(sgl, sg, nelems, i)
> arch_sync_dma_for_cpu(sg_phys(sg), sg->length, dir);
> }
I'd remove the above check and fold the if (!dev_is_dma_coherent(dev))
into the else line. Same for iommu_dma_sync_sg_for_device.
next prev parent reply other threads:[~2021-08-11 5:58 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 2:42 [PATCH v3 0/5] Fixes for dma-iommu swiotlb bounce buffers David Stevens
2021-08-11 2:42 ` [PATCH v3 1/5] dma-iommu: fix sync_sg with swiotlb David Stevens
2021-08-11 5:57 ` Christoph Hellwig [this message]
2021-08-11 18:22 ` Robin Murphy
2021-08-11 2:42 ` [PATCH v3 2/5] dma-iommu: fix arch_sync_dma for map David Stevens
2021-08-11 6:01 ` Christoph Hellwig
2021-08-11 18:47 ` Robin Murphy
2021-08-12 9:21 ` David Stevens
2021-08-12 10:38 ` Robin Murphy
2021-08-11 2:42 ` [PATCH v3 3/5] dma-iommu: add SKIP_CPU_SYNC after syncing David Stevens
2021-08-11 6:07 ` Christoph Hellwig
2021-08-11 19:00 ` Robin Murphy
2021-08-11 2:42 ` [PATCH v3 4/5] dma-iommu: Check CONFIG_SWIOTLB more broadly David Stevens
2021-08-11 19:02 ` Robin Murphy
2021-08-11 2:42 ` [PATCH v3 5/5] dma-iommu: account for min_align_mask David Stevens
2021-08-11 9:26 ` Mi, Dapeng1
2021-08-11 19:12 ` Robin Murphy
2021-08-12 1:45 ` David Stevens
2021-08-12 9:57 ` Robin Murphy
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