Re: [PATCH v2 3/3] arch/*/: remove CONFIG_VIRT_TO_BUS

Michael Schmitz
2022-06-28T23:09:15Z

Hi Arnd,

On 29/06/22 09:50, Arnd Bergmann wrote:
> On Tue, Jun 28, 2022 at 11:03 PM Michael Schmitz <schmitzmic@gmail.com> wrote:
>> On 28/06/22 19:03, Geert Uytterhoeven wrote:
>>>> The driver allocates bounce buffers using kmalloc if it hits an
>>>> unaligned data buffer - can such buffers still even happen these days?
>>> No idea.
>> Hmmm - I think I'll stick a WARN_ONCE() in there so we know whether this
>> code path is still being used.
> kmalloc() guarantees alignment to the next power-of-two size or
> KMALLOC_MIN_ALIGN, whichever is bigger. On m68k this means it
> is cacheline aligned.

And all SCSI buffers are allocated using kmalloc? No way at all for user
space to pass unaligned data?

(SCSI is a weird beast - I have used a SCSI DAT tape driver many many
years ago, which broke all sorts of assumptions about transfer block
sizes ... but that might actually have been in the v0.99 days, many
rewrites of SCSI midlevel ago).

Just being cautious, as getting any of this tested will be a stretch.

Cheers,

Michael

>
> Arnd