linux-kernel - Re: [PATCH 5.2 073/131] dma-direct: correct the physical addr in dma_direct_sync_sg_for

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Date:   Tue, 6 Aug 2019 08:41:43 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Fugang Duan <fugang.duan@....com>,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 5.2 073/131] dma-direct: correct the physical addr in
 dma_direct_sync_sg_for_cpu/device

On Mon, Aug 05, 2019 at 03:02:40PM +0200, Greg Kroah-Hartman wrote:
>[ Upstream commit 449fa54d6815be8c2c1f68fa9dbbae9384a7c03e ]
>
>dma_map_sg() may use swiotlb buffer when the kernel command line includes
>"swiotlb=force" or the dma_addr is out of dev->dma_mask range.  After
>DMA complete the memory moving from device to memory, then user call
>dma_sync_sg_for_cpu() to sync with DMA buffer, and copy the original
>virtual buffer to other space.
>
>So dma_direct_sync_sg_for_cpu() should use swiotlb physical addr, not
>the original physical addr from sg_phys(sg).
>
>dma_direct_sync_sg_for_device() also has the same issue, correct it as
>well.
>
>Fixes: 55897af63091("dma-direct: merge swiotlb_dma_ops into the dma_direct code")
>Signed-off-by: Fugang Duan <fugang.duan@....com>
>Reviewed-by: Robin Murphy <robin.murphy@....com>
>Signed-off-by: Christoph Hellwig <hch@....de>
>Signed-off-by: Sasha Levin <sashal@...nel.org>

I'm going to drop this one. There's a fix to it upstream, but the fix
also seems to want 0036bc73ccbe ("drm/msm: stop abusing dma_map/unmap for
cache") which we're not taking, so I'm just going to drop this one as
well.

If someone wants it in the stable trees, please send a tested backport.

--
Thanks,
Sasha