[PATCH v4 0/2] block: Enable proper MMIO memory handling for P2P DMA

[Leon Romanovsky]

On Thu, Nov 13, 2025 at 01:40:50PM -0700, Jens Axboe wrote:
> On 11/13/25 12:52 PM, Keith Busch wrote:
> > On Thu, Nov 13, 2025 at 10:45:53AM -0700, Jens Axboe wrote:
> >> I took a look, and what happens here is that iter.p2pdma.map is 0 as it
> >> never got set to anything. That is the same as PCI_P2PDMA_MAP_UNKNOWN,
> >> and hence we just end up in a BLK_STS_RESOURCE. First of all, returning
> >> BLK_STS_RESOURCE for that seems... highly suspicious. That should surely
> >> be a fatal error. And secondly, this just further backs up that there's
> >> ZERO testing done on this patchset at all. WTF?
> >>
> >> FWIW, the below makes it boot just fine, as expected, as a default zero
> >> filled iter then matches the UNKNOWN case.
> > 
> > I think this must mean you don't have CONFIG_PCI_P2PDMA enabled. The
> 
> Right, like most normal people :-)

It depends how you are declaring normal people :).
In my Fedora OS, installed on my laptop, CONFIG_PCI_P2PDMA is enabled by default.
https://src.fedoraproject.org/rpms/kernel/blob/rawhide/f/kernel-x86_64-fedora.config#_5567
and in RHEL too
https://src.fedoraproject.org/rpms/kernel/blob/rawhide/f/kernel-x86_64-rhel.config#_4964

Thanks