Re: [PATCH v3 12/16] PCI: Obey iomem restrictions for procfs mmap

[Jason Gunthorpe]

On Wed, Oct 21, 2020 at 09:24:08PM +0200, Daniel Vetter wrote:
> On Wed, Oct 21, 2020 at 6:37 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote:
> >
> > On Wed, Oct 21, 2020 at 05:54:54PM +0200, Daniel Vetter wrote:
> >
> > > The trouble is that io_remap_pfn adjust vma->pgoff, so we'd need to
> > > split that. So ideally ->mmap would never set up any ptes.
> >
> > /dev/mem makes pgoff == pfn so it doesn't get changed by remap.
> >
> > pgoff doesn't get touched for MAP_SHARED either, so there are other
> > users that could work like this - eg anyone mmaping IO memory is
> > probably OK.
> 
> I was more generally thinking for io_remap_pfn_users because of the
> mkwrite use-case we might have in fbdev emulation in drm.

You have a use case for MAP_PRIVATE and io_remap_pfn_range()??

Jason