On Fri, 28 Jul 2017 11:50:43 -0700
Feng Kan <fkan@xxxxxxx> wrote:
> The APM X-Gene PCIe root port does not support ACS at this point.
> However, the hw provides isolation and source validation through
> the SMMU. The stream ID generated by the PCIe ports contain both
> the BDF as well as the port ID in its 3 most significant bits.
> Turn on ACS but disable all the peer to peer features.
>
> Signed-off-by: Feng Kan <fkan@xxxxxxx>
> ---
> V3 Change: Add comment regarding unique port id in stream ID
> V2 Change: Move XGene ACS quirk to unique XGene function
>
> drivers/pci/quirks.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 085fb78..0f8f1cd 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4120,6 +4120,19 @@ static int pci_quirk_cavium_acs(struct pci_dev *dev, u16 acs_flags)
> return acs_flags ? 0 : 1;
> }
>
> +static int pci_quirk_xgene_acs(struct pci_dev *dev, u16 acs_flags)
> +{
> + /*
> + * XGene root matching this quirk do not allow peer-to-peer
> + * transactions with others, allowing masking out these bits as if they
> + * were unimplemented in the ACS capability.
> + */
> + acs_flags &= ~(PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR |
> + PCI_ACS_CR | PCI_ACS_UF | PCI_ACS_DT);
> +
> + return acs_flags ? 0 : 1;
> +}
> +
> /*
> * Many Intel PCH root ports do provide ACS-like features to disable peer
> * transactions and validate bus numbers in requests, but do not provide an
> @@ -4368,6 +4381,8 @@ static int pci_quirk_mf_endpoint_acs(struct pci_dev *dev, u16 acs_flags)
> { 0x10df, 0x720, pci_quirk_mf_endpoint_acs }, /* Emulex Skyhawk-R */
> /* Cavium ThunderX */
> { PCI_VENDOR_ID_CAVIUM, PCI_ANY_ID, pci_quirk_cavium_acs },
> + /* APM XGene */
> + { PCI_VENDOR_ID_AMCC, 0xE004, pci_quirk_xgene_acs },
> { 0 }
> };
>
Hi Feng,
Sorry, I have one more question as I happened to spend some time
looking at PCI_ACS_DT this week. DT specifies that peer-to-peer should
occur normally between egress ports for transactions which are
pre-translated by an ATS unit on the endpoint. Therefore if a root
port doesn't allow peer-to-peer, it seems like it should not claim to
support PCI_ACS_DT. I know your quirk is just a copy of the Cavium
one, but we should also go back and verify this question with them, or
perhaps I'm misinterpreting this capability. AIUI this is also a
performance capability, not an isolation capability, so it shouldn't
affect the ability to consider a device isolated, it only gets
confusing if we expect a performance benefit from this but don't
actually see one. Does your root port have this ability to
selectively allow peer-to-peer of pre-translated transactions? Thanks,
Alex
