linux-kernel - Re: [PATCH 3/3] vfio/pci: Enable VFIO_PCI

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Date: Thu, 23 May 2024 10:24:30 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: 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>,
        Alex
 Williamson <alex.williamson@...hat.com>,
        Gerd Bayer <gbayer@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 3/3] vfio/pci: Enable VFIO_PCI_MMAP for s390

On Wed, 2024-05-22 at 20:20 -0300, Jason Gunthorpe wrote:
> On Tue, May 21, 2024 at 02:14:59PM +0200, Niklas Schnelle 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 VFIO_PCI_MMAP can be enabled
> > on all s390 systems with native PCI allowing vfio-pci user-space
> > applications direct access to mapped resources.
> > 
> > Link: https://lore.kernel.org/all/c5ba134a1d4f4465b5956027e6a4ea6f6beff969.camel@linux.ibm.com/
> > Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> > ---
> >  drivers/vfio/pci/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> > index 15821a2d77d2..814aa0941d61 100644
> > --- a/drivers/vfio/pci/Kconfig
> > +++ b/drivers/vfio/pci/Kconfig
> > @@ -8,7 +8,7 @@ config VFIO_PCI_CORE
> >  	select IRQ_BYPASS_MANAGER
> >  
> >  config VFIO_PCI_MMAP
> > -	def_bool y if !S390
> > +	def_bool y
> >  	depends on VFIO_PCI_CORE
> 
> Should we just purge this kconfig entirely? It is never meaningfully n now?
> 
> Jason

Makes sense to me. Will change this for v2. I'll also add a Suggested-
by for you if that's okay, should probably have been in this version
already.

Thanks,
Niklas