On Wed, Feb 12, 2025 at 04:28:32PM +0100, Niklas Schnelle wrote: > On s390 there is a virtual PCI device called ISM which has a few > peculiarities. For one, it presents a 256 TiB PCI BAR whose size leads > to any attempt to ioremap() the whole BAR failing. This is problematic > since mapping the whole BAR is the default behavior of for example > vfio-pci in combination with QEMU and VFIO_PCI_MMAP enabled. > > Even if one tried to map this BAR only partially, the mapping would not > be usable without extra precautions on systems with MIO support enabled. > 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 through writeq()/readq() when MIO is in > use. > > In short the ISM device's BAR is not accessible through memory mappings. > Indicate this by introducing a new non_mappable_bars flag for the ISM > device and set it using a PCI quirk. Use this flag instead of the > VFIO_PCI_MMAP Kconfig option to block mapping with vfio-pci. This was > the only use of the Kconfig option so remove it. Note that there are no > PCI resource sysfs files on s390x already as HAVE_PCI_MMAP is currently > not set. If this were to be set in the future pdev->non_mappable_bars > can be used to prevent unusable resource files for ISM from being > created. > > As s390x has no PCI quirk handling add basic support modeled after x86's > arch/x86/pci/fixup.c and move the ISM device's PCI ID to the common > header to make it accessible. Also enable CONFIG_PCI_QUIRKS whenever > CONFIG_PCI is enabled. > > Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > +++ b/include/linux/pci_ids.h > @@ -518,6 +518,7 @@ > #define PCI_DEVICE_ID_IBM_ICOM_V2_ONE_PORT_RVX_ONE_PORT_MDM 0x0251 > #define PCI_DEVICE_ID_IBM_ICOM_V2_ONE_PORT_RVX_ONE_PORT_MDM_PCIE 0x0361 > #define PCI_DEVICE_ID_IBM_ICOM_FOUR_PORT_MODEL 0x252 > +#define PCI_DEVICE_ID_IBM_ISM 0x04ED Use lower-case hex to match other entries. > #define PCI_SUBVENDOR_ID_IBM 0x1014 > #define PCI_SUBDEVICE_ID_IBM_SATURN_SERIAL_ONE_PORT 0x03d4 > > -- > 2.45.2 >
