Re: [PATCH v2 2/3] vfio/pci: Tolerate oversized BARs by disallowing mmap

Matthew Rosato
2024-05-28T15:13:42Z

On 5/23/24 7:10 AM, 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().
>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---

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