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(-)

diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index bf50ffa10bde..c3bcb6911c53 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -7,10 +7,6 @@ config VFIO_PCI_CORE
 	select VFIO_VIRQFD
 	select IRQ_BYPASS_MANAGER
 
-config VFIO_PCI_MMAP
-	def_bool y if !S390
-	depends on VFIO_PCI_CORE
-
 config VFIO_PCI_INTX
 	def_bool y if !S390
 	depends on VFIO_PCI_CORE
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 0e9d46575776..c08d0f7bb500 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -120,9 +120,6 @@ static void vfio_pci_probe_mmaps(struct vfio_pci_core_device *vdev)
 
 		res = &vdev->pdev->resource[bar];
 
-		if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP))
-			goto no_mmap;
-
 		if (!(res->flags & IORESOURCE_MEM))
 			goto no_mmap;
 

-- 
2.40.1

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

> 
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index bf50ffa10bde..c3bcb6911c53 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -7,10 +7,6 @@ config VFIO_PCI_CORE
>  	select VFIO_VIRQFD
>  	select IRQ_BYPASS_MANAGER
>  
> -config VFIO_PCI_MMAP
> -	def_bool y if !S390
> -	depends on VFIO_PCI_CORE
> -
>  config VFIO_PCI_INTX
>  	def_bool y if !S390
>  	depends on VFIO_PCI_CORE
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 0e9d46575776..c08d0f7bb500 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -120,9 +120,6 @@ static void vfio_pci_probe_mmaps(struct vfio_pci_core_device *vdev)
>  
>  		res = &vdev->pdev->resource[bar];
>  
> -		if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP))
> -			goto no_mmap;
> -
>  		if (!(res->flags & IORESOURCE_MEM))
>  			goto no_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@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