From: Robin Murphy <robin.murphy@arm.com>
To: David Stevens <stevensd@chromium.org>, Christoph Hellwig <hch@lst.de>
Cc: Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Lu Baolu <baolu.lu@linux.intel.com>, Tom Murphy <murphyt7@tcd.ie>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 3/7] dma-iommu: skip extra sync during unmap w/swiotlb
Date: Thu, 19 Aug 2021 09:59:47 +0100 [thread overview]
Message-ID: <c1febb7b-8a79-c94b-5358-b6fb38c5a194@arm.com> (raw)
In-Reply-To: <20210817013852.3222824-4-stevensd@google.com>
On 2021-08-17 02:38, David Stevens wrote:
> From: David Stevens <stevensd@chromium.org>
>
> Calling the iommu_dma_sync_*_for_cpu functions during unmap can cause
> two copies out of the swiotlb buffer. Do the arch sync directly in
> __iommu_dma_unmap_swiotlb instead to avoid this. This makes the call to
> iommu_dma_sync_sg_for_cpu for untrusted devices in iommu_dma_unmap_sg no
> longer necessary, so move that invocation later in the function.
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: David Stevens <stevensd@chromium.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/iommu/dma-iommu.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 8098ce593640..5dd2c517dbf5 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -504,6 +504,9 @@ static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr,
> if (WARN_ON(!phys))
> return;
>
> + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && !dev_is_dma_coherent(dev))
> + arch_sync_dma_for_cpu(phys, size, dir);
> +
> __iommu_dma_unmap(dev, dma_addr, size);
>
> if (unlikely(is_swiotlb_buffer(phys)))
> @@ -853,8 +856,6 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
> size_t size, enum dma_data_direction dir, unsigned long attrs)
> {
> - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> - iommu_dma_sync_single_for_cpu(dev, dma_handle, size, dir);
> __iommu_dma_unmap_swiotlb(dev, dma_handle, size, dir, attrs);
> }
>
> @@ -1062,14 +1063,14 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
> struct scatterlist *tmp;
> int i;
>
> - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> - iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir);
> -
> if (dev_is_untrusted(dev)) {
> iommu_dma_unmap_sg_swiotlb(dev, sg, nents, dir, attrs);
> return;
> }
>
> + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> + iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir);
> +
> /*
> * The scatterlist segments are mapped into a single
> * contiguous IOVA allocation, so this is incredibly easy.
>
next prev parent reply other threads:[~2021-08-19 8:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-17 1:38 [PATCH v6 0/7] Fixes for dma-iommu swiotlb bounce buffers David Stevens
2021-08-17 1:38 ` [PATCH v6 1/7] dma-iommu: fix sync_sg with swiotlb David Stevens
2021-08-17 1:38 ` [PATCH v6 2/7] dma-iommu: fix arch_sync_dma for map David Stevens
2021-08-19 8:59 ` Robin Murphy
2021-08-17 1:38 ` [PATCH v6 3/7] dma-iommu: skip extra sync during unmap w/swiotlb David Stevens
2021-08-19 8:59 ` Robin Murphy [this message]
2021-08-17 1:38 ` [PATCH v6 4/7] dma-iommu: fold _swiotlb helpers into callers David Stevens
2021-08-19 9:00 ` Robin Murphy
2021-08-17 1:38 ` [PATCH v6 5/7] dma-iommu: Check CONFIG_SWIOTLB more broadly David Stevens
2021-08-17 1:38 ` [PATCH v6 6/7] swiotlb: support aligned swiotlb buffers David Stevens
2021-08-17 1:38 ` [PATCH v6 7/7] dma-iommu: account for min_align_mask David Stevens
2021-08-19 9:03 ` Robin Murphy
2021-08-19 10:05 ` David Stevens
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=c1febb7b-8a79-c94b-5358-b6fb38c5a194@arm.com \
--to=robin.murphy@arm.com \
--cc=baolu.lu@linux.intel.com \
--cc=hch@lst.de \
--cc=iommu@lists.linux-foundation.org \
--cc=joro@8bytes.org \
--cc=linux-kernel@vger.kernel.org \
--cc=murphyt7@tcd.ie \
--cc=stevensd@chromium.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).