Re: [PATCH v4 4/4] vfio/pci: Enable PCI resource mmap() on s390 and remove VFIO_PCI_MMAP

Niklas Schnelle
2024-07-11T10:20:35Z

On Thu, 2024-07-04 at 10:16 -0600, Alex Williamson wrote:
> On Wed, 26 Jun 2024 13:15:51 +0200
> Niklas Schnelle <schnelle@linux.ibm.com> wrote:
>
> > With the introduction of memory I/O (MIO) instructions enbaled in commit
> > 71ba41c9b1d9 ("s390/pci: provide support for MIO instructions") s390
> > gained support for direct user-space access to mapped PCI resources.
> > Even without those however user-space can access mapped PCI resources
> > via the s390 specific MMIO syscalls. Thus mmap() can and should be
> > supported on all s390 systems with native PCI. Since VFIO_PCI_MMAP
> > enablement for s390 would make it unconditionally true and thus
> > pointless just remove it entirely.
> >
> > Link: https://lore.kernel.org/all/c5ba134a1d4f4465b5956027e6a4ea6f6beff969.camel@linux.ibm.com/
> > Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> > Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
> > Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> > ---
> > drivers/vfio/pci/Kconfig | 4 ----
> > drivers/vfio/pci/vfio_pci_core.c | 3 ---
> > 2 files changed, 7 deletions(-)
>
> I think you're planning a v5 which drops patch 3/ of this series and
> finesses the commit log of patch 2/ a bit. This has become much less a
> vfio series, so if you want to commit through s390,
>
> Acked-by: Alex Williamson <alex.williamson@redhat.com>
>
> Thanks,
> Alex
>

Thank you! Yes I will send a v5. I actually already pushed a changed
version to my git.kernel.org branch but we're still discussing
internally because pdev->non_compliant_bars respectively the resulting
removal of the resources is interfering with future work on user-space
vfio-pci use of the ISM device with a vfio-pci-ism variant driver.

Thanks,
Niklas