On 24/02/19 12:24PM, Bean Huo wrote:
> From: Bean Huo <beanhuo@xxxxxxxxxx>
>
> As per PCIe r6.2, sec 6.13 titled "Alternative Routing-ID Interpretation
> (ARI)", up to 8 [fn # 0..7] Physical Functions(PFs) are allowed in an
> non-ARI capable device. Previously, our implementation erroneously limited
> the maximum number of PFs to 7 for endpoints without ARI support.
>
> This patch corrects the maximum PF count to adhere to the PCIe specification
> by allowing up to 8 PFs on non-ARI capable devices. This change ensures better
> compliance with the standard and improves compatibility with devices relying
> on this specification.
The function "next_fn()" seems to provide the next valid function.
Therefore, if the current function is 0 (fn = 0), then the next valid
function will be 1 which is returned by next_fn(). It extends similarly
until the case where current function is 6 (fn = 6) which shall return
the next valid function as 7. So all 8 PFs are still treated as valid
and there doesn't seem to be any limitation. Only in the case where the
EP doesn't support ARI (there is no function 8 (fn = 8)), the call to
next_fn() with the fn parameter set to 7, will return -ENODEV which
seems to be the expected behavior.
Regards,
Siddharth.
>
> Fixes: c3df83e01a96 ("PCI: Clean up pci_scan_slot()")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Bean Huo <beanhuo@xxxxxxxxxx>
> ---
> Changelog:
> v2--v3:
> 1. Update commit messag
> v1--v2:
> 1. Add Fixes tag
> 2. Modify commit message
> ---
> drivers/pci/probe.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index ed6b7f48736a..8c3d0f63bc13 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2630,7 +2630,8 @@ static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)
> if (pci_ari_enabled(bus))
> return next_ari_fn(bus, dev, fn);
>
> - if (fn >= 7)
> + /* If EP does not support ARI, the maximum number of functions should be 7 */
> + if (fn > 7)
> return -ENODEV;
> /* only multifunction devices may have more functions */
> if (dev && !dev->multifunction)
> --
> 2.34.1
>
>
