Re: [PATCH v2 08/22] iommufd: Abstract iopt_pin_pages and iopt_unpin_pages helpers

Nicolin Chen
2025-05-05T15:44:52Z

On Mon, May 05, 2025 at 12:01:09PM -0300, Jason Gunthorpe wrote:
> On Mon, Apr 28, 2025 at 10:41:45AM -0700, Nicolin Chen wrote:
> > > I'm uncertain, but perhaps pr_warn_ratelimited() would be a better
> > > alternative to WARN_ON() here? WARN_ON_ONCE() generates warning messages
> > > with kernel call traces in the kernel messages, which might lead users
> > > to believe that something serious has happened in the kernel.
> >
> > We already have similar practice, e.g. iommufd_hwpt_nested_alloc.
> >
> > In my review, a WARN_ON/WARN_ON_ONCE means there is a kernel bug,
> > which shouldn't occur in the first place and isn't something that
>
> Right, so it should never happen from any ioctl path and syzkaller
> should never trigger it based on system call randomization
>
> Is that what this achieves?

The functions would be still used in the kernel path. So, I think
we need to retain these warnings for that. But given that an ioctl
could trigger a series of WARN_ONs, WARN_ON_ONCE is something that
wouldn't bother user space a lot while it provides the kernel path
enough info to debug.

Thanks
Nicolin