On Wed, 2024-06-19 at 21:09 -0700, Christoph Hellwig wrote: > On Wed, Jun 19, 2024 at 12:56:47PM +0200, Niklas Schnelle wrote: > > In short, the ISM BAR 0 is stupidly large but this is intentional. It > > not fitting in the VMAP is simply the least crazy filter I could come > > up with to keep the ISM device from causing trouble for use of vfio-pci > > mmap() for other, normal, PCI devices. > > Then maybe add a PCI quirk to prevent mapping it. This would also > affect the sysfs resource0 file unless I'm missing something. > The resource<N> files are globally disabled on s390x due to lack of HAVE_PCI_MMAP/ARCH_GENERIC_PCI_MMAP_RESOURCE at the moment. I might change that in the future with a analogous argument as for VFIO_PCI_MMAP but for its not there. Once we add it we of course need the same special ISM treatment there too. Looking at the existing PCI quirks I don't see anything that would fit so I'm guessing you would want to add a new quirk? As I understand it we would then have to export something like a is_pci_mmap_broken(pdev) function while currently the only quirk function that seems to be exported is pxi_fixup_device(). But then what happens if CONFIG_PCI_QUIRKS=n? Also the header comment in drivers/pci/quirks.c says that platform specific devices shouldn't go in there and ISM is platform specific. Instead of exporting IOREMAP_START/IOREMAP_END maybe there is another reasonable maximum resource length? Or maybe we could create a size_t ioremap_area_size() helper similar to is_ioremap_addr() but not inlined. The latter already uses IOREMAP_START/IOREMAP_END so not sure how that works when IOREMAP_END is not exported? Thanks, Niklas
