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

[Will Deacon]

On Wed, Jun 30, 2021 at 08:56:51AM -0700, Nathan Chancellor wrote:
> On Wed, Jun 30, 2021 at 12:43:48PM +0100, Will Deacon wrote:
> > On Wed, Jun 30, 2021 at 05:17:27PM +0800, Claire Chang wrote:
> > > `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'm less sure about this. 'dma_io_tlb_mem' should be pointing at
> > 'io_tlb_default_mem', which is a page-aligned allocation from memblock.
> > The spinlock is at offset 0x24 in that structure, and looking at the
> > register dump from the crash:
> > 
> > Jun 29 18:28:42 hp-4300G kernel: RSP: 0018:ffffadb4013db9e8 EFLAGS: 00010006
> > Jun 29 18:28:42 hp-4300G kernel: RAX: 00000000003a8290 RBX: 0000000000000000 RCX: ffff8900572ad580
> > Jun 29 18:28:42 hp-4300G kernel: RDX: ffff89005653f024 RSI: 00000000000c0000 RDI: 0000000000001d17
> > Jun 29 18:28:42 hp-4300G kernel: RBP: 000000000a20d000 R08: 00000000000c0000 R09: 0000000000000000
> > Jun 29 18:28:42 hp-4300G kernel: R10: 000000000a20d000 R11: ffff89005653f000 R12: 0000000000000212
> > Jun 29 18:28:42 hp-4300G kernel: R13: 0000000000001000 R14: 0000000000000002 R15: 0000000000200000
> > Jun 29 18:28:42 hp-4300G kernel: FS:  00007f1f8898ea40(0000) GS:ffff890057280000(0000) knlGS:0000000000000000
> > Jun 29 18:28:42 hp-4300G kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > Jun 29 18:28:42 hp-4300G kernel: CR2: 00000000003a8290 CR3: 00000001020d0000 CR4: 0000000000350ee0
> > Jun 29 18:28:42 hp-4300G kernel: Call Trace:
> > Jun 29 18:28:42 hp-4300G kernel:  _raw_spin_lock_irqsave+0x39/0x50
> > Jun 29 18:28:42 hp-4300G kernel:  swiotlb_tbl_map_single+0x12b/0x4c0
> > 
> > Then that correlates with R11 holding the 'dma_io_tlb_mem' pointer and
> > RDX pointing at the spinlock. Yet RAX is holding junk :/
> > 
> > I agree that enabling KASAN would be a good idea, but I also think we
> > probably need to get some more information out of swiotlb_tbl_map_single()
> > to see see what exactly is going wrong in there.
> 
> I can certainly enable KASAN and if there is any debug print I can add
> or dump anything, let me know!

I bit the bullet and took v5.13 with swiotlb/for-linus-5.14 merged in, built
x86 defconfig and ran it on my laptop. However, it seems to work fine!

Please can you share your .config?

Will