On Wed, 28 Oct 2020 16:15:45 -0700
Rajat Jain <raja...@google.com> wrote:
> Some devices may have have anomalies with the ACS cpability structure,
> and they may be using quirks to support ACS functionality via other
> registers. For such devices, it is important we always call
> pci_enable_acs() to give the quirks a chance to enable ACS in other ways.
>
> For Eg:
> There seems a class of Intel devices quirked with *_intel_pch_acs_*
> functions, that do not expose the standard ACS capability structure. But
> these quirks help support ACS on these devices using other registers:
> pci_quirk_enable_intel_pch_acs() -> doesn't use acs_cap to enable ACS
>
> This has already been taken care of in the quirks, in the other direction
> i.e. when checking if the ACS is enabled or not. So no need to do
> anything there.
>
> Reported-by: Boris V <bori...@bstnet.org>
> Fixes: 52fbf5bdeeef ("PCI: Cache ACS capability offset in device")
> Signed-off-by: Rajat Jain <raja...@google.com>
> ---
> drivers/pci/pci.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 6d4d5a2f923d..ab398226c55e 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3516,8 +3516,13 @@ void pci_acs_init(struct pci_dev *dev)
> {
> dev->acs_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
>
> - if (dev->acs_cap)
> - pci_enable_acs(dev);
> + /*
> + * Attempt to enable ACS regardless of capability because some rootports
> + * (e.g. the ones quirked with *_intel_pch_acs_*) may not expose
> + * standard rootport capability structure, but still may support ACS via
> + * those quirks.
> + */
> + pci_enable_acs(dev);
> }
>
> /**
Much needed regression fix for v5.9:
Reviewed-by: Alex Williamson <alex.william...@redhat.com>
