The size field of the IGD OpRegion table is supposed to indicate table size in KB, but we've seen at least one report of a BIOS that appears to incorrectly report size in bytes. The default size is 8 (*1024 = 8KB), but an incorrect implementation may report 8192 (*1024 = 8MB) and can cause a variety of mapping errors. It's believed that 8MB would be an implausible, if not absurd, actual size, so we can probably be pretty safe in assuming this is a BIOS bug where the intended size is likely 8KB. Reported-by: Travis Faulhaber <tkffaul@xxxxxxxxxxx> Tested-by: Travis Faulhaber <tkffaul@xxxxxxxxxxx> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> --- drivers/vfio/pci/vfio_pci_igd.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/pci/vfio_pci_igd.c b/drivers/vfio/pci/vfio_pci_igd.c index 228df565e9bc..c89a4797cd18 100644 --- a/drivers/vfio/pci/vfio_pci_igd.c +++ b/drivers/vfio/pci/vfio_pci_igd.c @@ -86,7 +86,16 @@ static int vfio_pci_igd_opregion_init(struct vfio_pci_device *vdev) return -EINVAL; } - size *= 1024; /* In KB */ + /* + * The OpRegion size field is specified as size in KB, but there have been + * user reports where this field appears to report size in bytes. If we + * read 8192, assume this is the case. + */ + if (size == OPREGION_SIZE) + pci_warn(vdev->pdev, + "BIOS Bug, IGD OpRegion reports invalid size, assuming default 8KB\n"); + else + size *= 1024; /* In KB */ /* * Support opregion v2.1+
