I noticed that after kernel commit abafbc55 'vfio-pci: Invalidate mmaps and block MMIO access on disabled memory' vfio-pci via qemu on s390x fails spectacularly, with errors in qemu like:
qemu-system-s390x: vfio_region_read(0001:00:00.0:region0+0x0, 4) failed: Input/output error >From read to bar 0 originating out of hw/s390x/s390-pci-inst.c:zpci_read_bar(). So, I'm trying to figure out how to get vfio-pci happy again on s390x. From a bit of tracing, we seem to be triggering the new trap in __vfio_pci_memory_enabled(). Sure enough, if I just force this function to return 'true' as a test case, things work again. The included patch attempts to enforce the setting, which restores everything to working order but also triggers vfio_bar_restore() in the process.... So this isn't the right answer, more of a proof-of-concept. @Alex: Any guidance on what needs to happen to make qemu-s390x happy with this recent kernel change? @Nilkas/@Pierre: I wonder if this might be related to host device is_virtfn? I note that my host device lspci output looks like: 0000:00:00.0 Ethernet controller: Mellanox Technologies MT27710 Family [ConnectX-4 Lx Virtual Function] But the device is not marked as is_virtfn.. Otherwise, Alex's fix from htps://lkml.org/lkml/2020/6/25/628 should cover the case. Matthew Rosato (1): s390x/pci: Enforce PCI_COMMAND_MEMORY for vfio-pci hw/s390x/s390-pci-inst.c | 10 ++++++++++ 1 file changed, 10 insertions(+) -- 1.8.3.1