On 2021.05.07 12:53:17 -0600, Alex Williamson wrote: > 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+ > Reviewed-by: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx> thanks
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