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@linux.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
 
 config VFIO_PCI_INTX

-- 
2.40.1

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@linux.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

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@linux.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