[PATCH v15 06/12] swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing

[Claire Chang]

On Wed, Jun 30, 2021 at 9:43 AM Nathan Chancellor <nathan at kernel.org> wrote:
>
> On Thu, Jun 24, 2021 at 11:55:20PM +0800, Claire Chang wrote:
> > Propagate the swiotlb_force into io_tlb_default_mem->force_bounce and
> > use it to determine whether to bounce the data or not. This will be
> > useful later to allow for different pools.
> >
> > Signed-off-by: Claire Chang <tientzu at chromium.org>
> > Reviewed-by: Christoph Hellwig <hch at lst.de>
> > Tested-by: Stefano Stabellini <sstabellini at kernel.org>
> > Tested-by: Will Deacon <will at kernel.org>
> > Acked-by: Stefano Stabellini <sstabellini at kernel.org>
>
> This patch as commit af452ec1b1a3 ("swiotlb: Use is_swiotlb_force_bounce
> for swiotlb data bouncing") causes my Ryzen 3 4300G system to fail to
> get to an X session consistently (although not every single time),
> presumably due to a crash in the AMDGPU driver that I see in dmesg.
>
> I have attached logs at af452ec1b1a3 and f127c9556a8e and I am happy
> to provide any further information, debug, or test patches as necessary.

Are you using swiotlb=force? or the swiotlb_map is called because of
!dma_capable? (https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/kernel/dma/direct.h#n93)

`BUG: unable to handle page fault for address: 00000000003a8290` and
the fact it crashed at `_raw_spin_lock_irqsave` look like the memory
(maybe dev->dma_io_tlb_mem) was corrupted?
The dev->dma_io_tlb_mem should be set here
(https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/pci/probe.c#n2528)
through device_initialize.

I can't tell what happened from the logs, but maybe we could try KASAN
to see if it provides more clue.

Thanks,
Claire

>
> Cheers,
> Nathan