On Fri, 01 May 2020 15:41:24 -0600 Alex Williamson <[email protected]> wrote:
> There is no PCI spec defined capability with ID 0, therefore we don't > expect to find it in a capability chain and we use this index in an > internal array for tracking the sizes of various capabilities to handle > standard config space. Therefore if a device does present us with a > capability ID 0, we mark our capability map with nonsense that can > trigger conflicts with other capabilities in the chain. Ignore ID 0 > when walking the capability chain, handling it as a hidden capability. > > Seen on an NVIDIA Tesla T4. > > Signed-off-by: Alex Williamson <[email protected]> > --- > drivers/vfio/pci/vfio_pci_config.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/vfio/pci/vfio_pci_config.c > b/drivers/vfio/pci/vfio_pci_config.c > index 87d0cc8c86ad..5935a804cb88 100644 > --- a/drivers/vfio/pci/vfio_pci_config.c > +++ b/drivers/vfio/pci/vfio_pci_config.c > @@ -1487,7 +1487,7 @@ static int vfio_cap_init(struct vfio_pci_device *vdev) > if (ret) > return ret; > > - if (cap <= PCI_CAP_ID_MAX) { Maybe add a comment: /* no PCI spec defined capability with ID 0: hide it */ ? > + if (cap && cap <= PCI_CAP_ID_MAX) { > len = pci_cap_length[cap]; > if (len == 0xFF) { /* Variable length */ > len = vfio_cap_len(vdev, cap, pos); > Is there a requirement for caps to be strictly ordered? If not, could len hold a residual value from a previous iteration?
