On Fri, 01 May 2020 15:41:24 -0600
Alex Williamson <alex.williamson@xxxxxxxxxx> 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 <alex.williamson@xxxxxxxxxx>
> ---
> 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?
