Re: [PATCH v14 06/12] swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing

[Claire Chang <tientzu@xxxxxxxxxxxx>]

On Thu, Jun 24, 2021 at 1:43 PM Christoph Hellwig <hch@xxxxxx> wrote:
>
> On Wed, Jun 23, 2021 at 02:44:34PM -0400, Qian Cai wrote:
> > is_swiotlb_force_bounce at /usr/src/linux-next/./include/linux/swiotlb.h:119
> >
> > is_swiotlb_force_bounce() was the new function introduced in this patch 
> > here.
> >
> > +static inline bool is_swiotlb_force_bounce(struct device *dev)
> > +{
> > +     return dev->dma_io_tlb_mem->force_bounce;
> > +}
>
> To me the crash looks like dev->dma_io_tlb_mem is NULL.  Can you
> turn this into :
>
>         return dev->dma_io_tlb_mem && dev->dma_io_tlb_mem->force_bounce;
>
> for a quick debug check?

I just realized that dma_io_tlb_mem might be NULL like Christoph
pointed out since swiotlb might not get initialized.
However,  `Unable to handle kernel paging request at virtual address
dfff80000000000e` looks more like the address is garbage rather than
NULL?
I wonder if that's because dev->dma_io_tlb_mem is not assigned
properly (which means device_initialize is not called?).