Re: [PATCH v6 3/3] mm/gup: disallow FOLL_LONGTERM GUP-fast writing to file-backed mappings

[David Hildenbrand]

On 02.05.23 15:10, Jason Gunthorpe wrote:
> On Tue, May 02, 2023 at 03:04:27PM +0200, Christian Borntraeger wrote:
> \> > We can reintroduce a flag to permit exceptions if this is really broken, are you
> > > able to test? I don't have an s390 sat around :)
> >
> > Matt (Rosato on cc) probably can. In the end, it would mean having
> >    <memoryBacking>
> >      <source type="file"/>
> >    </memoryBacking>
>
> This s390 code is the least of the problems, after this series VFIO
> won't startup at all with this configuration.

Good question if the domain would fail to start. I recall that IOMMUs 
for zPCI are special on s390x. [1]

Well, zPCI is special. I cannot immediately tell when we would trigger 
long-term pinning.

[1] https://www.mail-archive.com/qemu-devel@xxxxxxxxxx/msg875728.html

--
Thanks,

David / dhildenb