Re: [PATCH 2/3] vfio/pci: Tolerate oversized BARs by disallowing mmap

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, May 21, 2024 at 02:14:58PM +0200, Niklas Schnelle 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().
> 
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

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

Jason