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

On Wed, Jun 30, 2021 at 9:43 AM Nathan Chancellor [off-list ref] wrote:

On Thu, Jun 24, 2021 at 11:55:20PM +0800, Claire Chang wrote:

quoted

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 <redacted>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Will Deacon <will@kernel.org>
Acked-by: Stefano Stabellini <sstabellini@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