Re: [PATCH] mm/x86/pat: Only untrack the pfn range if unmap region

Peter Xu
2024-07-17T18:12:54Z

On Wed, Jul 17, 2024 at 06:32:05PM +0200, David Hildenbrand wrote:
> On 17.07.24 18:30, Peter Xu wrote:
> > On Wed, Jul 17, 2024 at 04:17:12PM +0200, David Hildenbrand wrote:
> > > I'd be curious how a previous truncation on a file can tear down a PFNMAP
> > > mapping -- and if there are simple ways to forbid that (if possible).
> >
> > Unfortunately, forbiding it may not work for vfio, as vfio would like to
> > allow none (or partial) mapping on the bars.. at least so far that's the
> > plan.
>
> I think vfio should handle that memtype reservation manually, as you
> proposed. So that shouldn't block that IIUC.

Oh, so maybe I misunderstood here. As long as we can live with VFIO's vma
(with the pfn tracking on top, but without pgtable installed) I think it
should be fine.

Thanks,

--
Peter Xu