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

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Message-ID: <15f117b4a9e0481aaa6fd5848a58d16900a65679.camel@linux.ibm.com>
Date: Thu, 11 Jul 2024 12:20:14 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: Bjorn Helgaas <helgaas@...nel.org>, Christoph Hellwig <hch@....de>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens
 <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>,
        Christian Borntraeger
 <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Gerd
 Bayer <gbayer@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v4 4/4] vfio/pci: Enable PCI resource mmap() on s390 and
 remove VFIO_PCI_MMAP

On Thu, 2024-07-04 at 10:16 -0600, Alex Williamson wrote:
> On Wed, 26 Jun 2024 13:15:51 +0200
> Niklas Schnelle <schnelle@...ux.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@...dia.com>
> > Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> > Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> > Signed-off-by: Niklas Schnelle <schnelle@...ux.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@...hat.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