On Wed, 29 May 2024 13:36:25 +0200
Niklas Schnelle <schnelle@xxxxxxxxxxxxx> wrote:
> On s390 there is a virtual PCI device called ISM which has a few rather
> annoying oddities. For one it claims to have a 256 TiB PCI BAR (not
> a typo) which leads to any attempt to mmap() it failing during vmap.
>
> Even if one tried to map this "BAR" only partially the mapping would not
> be usable on systems with MIO support enabled however. This is because
> of another oddity in that this virtual PCI device does not support the
> newer memory I/O (MIO) PCI instructions and legacy PCI instructions are
> not accessible by user-space when MIO is in use. If this device needs to
> be accessed by user-space it will thus need a vfio-pci variant driver.
> Until then work around both issues by excluding resources which don't
> fit between IOREMAP_START and IOREMAP_END in vfio_pci_probe_mmaps().
>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Reviewed-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
> Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
> ---
> drivers/vfio/pci/vfio_pci_core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 80cae87fff36..0f1ddf2d3ef2 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -28,6 +28,7 @@
> #include <linux/nospec.h>
> #include <linux/sched/mm.h>
> #include <linux/iommufd.h>
> +#include <linux/ioremap.h>
> #if IS_ENABLED(CONFIG_EEH)
> #include <asm/eeh.h>
> #endif
> @@ -129,9 +130,12 @@ static void vfio_pci_probe_mmaps(struct vfio_pci_core_device *vdev)
> /*
> * The PCI core shouldn't set up a resource with a
> * type but zero size. But there may be bugs that
> - * cause us to do that.
> + * cause us to do that. There is also at least one
> + * device which advertises a resource too large to
> + * ioremap().
> */
> - if (!resource_size(res))
> + if (!resource_size(res) ||
> + resource_size(res) > (IOREMAP_END + 1 - IOREMAP_START))
> goto no_mmap;
>
> if (resource_size(res) >= PAGE_SIZE) {
>
A powerpc build reports:
ERROR: modpost: "__kernel_io_end" [drivers/vfio/pci/vfio-pci-core.ko] undefined!
Looks like only __kernel_io_start is exported. Thanks,
Alex
