Re: [PATCH 5.2 073/131] dma-direct: correct the physical addr in dma_direct_sync_sg_for_cpu/device

[Robin Murphy]

On 06/08/2019 13:41, Sasha Levin wrote:
> 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@xxxxxxx>
> > Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> 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.

Given that the two commits touch entirely separate files I'm not sure 
what the imagined dependency could be :/

0036bc73ccbe is indeed not a fix (frankly I'm not convinced it's even a 
valid change at all) but even conceptually it bears no relation 
whatsoever to the genuine bug fixed by 449fa54d6815.

Robin.

> If someone wants it in the stable trees, please send a tested backport.
>
> --
> Thanks,
> Sasha