On Thu, 14 Feb 2019 19:27:15 +0100 Auger Eric <[email protected]> wrote:
> Hi Alex, > > On 2/13/19 6:52 PM, Alex Williamson wrote: > > On Wed, 13 Feb 2019 12:06:10 +0100 > > Eric Auger <[email protected]> wrote: > > > >> pci_map_rom/pci_get_rom_size() performs memory access in the ROM. > >> In case the Memory Space accesses were disabled, readw() is likely to > >> crash the host with a synchronous external abort (aarch64). > > > > As implied in response to Konrad, the likeliness really depends on the > > whole platform, not just the CPU architecture. It's a class of > > problems that depends on OS control or error handling, which we simply > > don't have on many systems. But we can fix this instance of it. > > Agreed, I just hit this issue on one specific aarch64 machine > > > >> In case memory accesses were disabled, re-enable them before the call > >> and disable them back again just after. > >> > >> Signed-off-by: Eric Auger <[email protected]> > > > > This has been around since the beginning, but maybe a Fixes tag would > > be useful: > > > > Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver") > OK > > > >> > >> --- > >> > >> v1 -> v2: > >> - also re-enable in case of error > >> --- > >> drivers/vfio/pci/vfio_pci.c | 17 ++++++++++++++++- > >> 1 file changed, 16 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c > >> index ff60bd1ea587..721aa55424a4 100644 > >> --- a/drivers/vfio/pci/vfio_pci.c > >> +++ b/drivers/vfio/pci/vfio_pci.c > >> @@ -706,8 +706,10 @@ static long vfio_pci_ioctl(void *device_data, > >> break; > >> case VFIO_PCI_ROM_REGION_INDEX: > >> { > >> + bool mem_access_disabled; > >> void __iomem *io; > >> size_t size; > >> + u16 cmd; > >> > >> info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index); > >> info.flags = 0; > >> @@ -723,15 +725,28 @@ static long vfio_pci_ioctl(void *device_data, > >> break; > >> } > >> > >> + pci_read_config_word(pdev, PCI_COMMAND, &cmd); > >> + mem_access_disabled = !(cmd & PCI_COMMAND_MEMORY); > >> + if (mem_access_disabled) { > >> + cmd |= PCI_COMMAND_MEMORY; > >> + pci_write_config_word(pdev, PCI_COMMAND, cmd); > >> + } > >> + > >> /* Is it really there? */ > >> io = pci_map_rom(pdev, &size); > >> if (!io || !size) { > >> info.size = 0; > >> - break; > >> + goto rom_info_out; > >> } > >> pci_unmap_rom(pdev, io); > >> > >> info.flags = VFIO_REGION_INFO_FLAG_READ; > >> +rom_info_out: > >> + if (mem_access_disabled) { > >> + cmd &= ~PCI_COMMAND_MEMORY; > >> + pci_write_config_word(pdev, PCI_COMMAND, cmd); > >> + } > >> + > >> break; > >> } > >> case VFIO_PCI_VGA_REGION_INDEX: > > > > I don't think we need to be so timid about the command register and we > > can also avoid the goto by modifying the test (testing io and size in > > the original is probably overly paranoid), perhaps simply: > Yes looks fine. > > Do you want to respin or do you prefer I do? Please take it, test it, and repost it, I haven't tested it at all. Thanks, Alex
