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

On 5/2/23 9:28 AM, David Hildenbrand wrote:

On 02.05.23 15:10, Jason Gunthorpe wrote:

quoted

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

quoted

quoted

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]

Eh, well what you referenced there never merged.  We will eventually do something like this, but via iommufd.  But right now s390 is still using vfio type1 iommu

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

Enabling a zPCI device in a QEMU guest when using zPCI interpretation facilities

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