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>
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 15821a2d77d2..9c88e3a6d06b 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 23961299b695..35b8e8f214af 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -121,9 +121,6 @@ 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 5/23/24 7:10 AM, 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 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>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>

Also sanity tested on s390 with mlx, nvme, ISM over vfio-pci (the latter of which triggers the patch 2 scenario).

On Thu, May 23, 2024 at 01:10:16PM +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 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>
> 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(-)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason