Re: [PATCH] vfio/type1: Cleanup remaining vaddr removal/update fragments

Jason Gunthorpe
2022-12-12T23:09:07Z

On Mon, Dec 12, 2022 at 02:26:51PM -0700, Alex Williamson wrote:
> On Mon, 12 Dec 2022 15:59:11 -0500
> Steven Sistare <steven.sistare@oracle.com> wrote:
>
> > On 12/12/2022 10:58 AM, Alex Williamson wrote:
> > > On Mon, 12 Dec 2022 09:17:54 -0400
> > > Jason Gunthorpe <jgg@ziepe.ca> wrote:
> > >
> > >> On Sat, Dec 10, 2022 at 09:14:06AM -0500, Steven Sistare wrote:
> > >>
> > >>> Thank you for your thoughtful response. Rather than debate the degree of
> > >>> of vulnerability, I propose an alternate solution. The technical crux of
> > >>> the matter is support for mediated devices.
> > >>
> > >> I'm not sure I'm convinced about that. It is easy to make problematic
> > >> situations with mdevs, but that doesn't mean other cases don't exist
> > >> too eg what happens if userspace suspends and then immediately does
> > >> something to trigger a domain attachment? Doesn't it still deadlock
> > >> the kernel?
> > >
> > > The opportunity for that to deadlock isn't obvious to me, a replay
> > > would be stalled waiting for invalid vaddrs, but this is essentially
> > > the user deadlocking themselves. There's also code there to handle the
> > > process getting killed while waiting, making it interruptible. Thanks,
> >
> > I will submit new patches tomorrow to exclude mdevs. Almost done.
>
> I've dropped the removal commits from my next branch in the interim.

Woah, please don't do that - I already built and sent pull requests
assuming this, there are conflicts.

Why would we not revert everything from 6.2 - that is what we agreed
to do?

Jason