Re: [PATCH] PCI/P2PDMA: Avoid returning a provider for non_mappable_bars

Leon Romanovsky
2026-04-22T15:19:11Z

On Wed, Apr 22, 2026 at 03:22:53PM +0100, Matt Evans wrote:
> Hi Leon,
>
> On 21/04/2026 20:49, Leon Romanovsky wrote:
> >
> > On Tue, Apr 21, 2026 at 10:43:51AM -0700, Matt Evans wrote:
> > > Extend pcim_p2pdma_provider()'s checks to exclude functions that have
> > > pdev->non_mappable_bars set.
> > >
> > > Consumers such as VFIO were previously able to map these for access by
> > > the CPU or P2P. Update the comment on non_mappable_bars to show it
> > > refers to any access, not just userspace CPU access.
> > >
> > > Fixes: 372d6d1b8ae3c ("PCI/P2PDMA: Refactor to separate core P2P functionality from memory allocation")
> >
> > I don't object to the patch, but this Fixes line doesn't look correct.
> > non_mappable_bars applies only to s390, which doesn't support p2p. That
> > wasn't prevented before 372d6d1b8ae3c refactoring too.
>
> Thanks; I'd chosen that commit as it adds the function that the additional
> test is being added to.

Can I suggest slightly different solution?
If CONFIG_..._S390 is set, we will unset CONFIG_PCI_P2PDMA and pcim_p2pdma_provider()
will be compiled to return NULL, without changing non_mappable_bars
description.

Thanks