Re: [PATCH v11 04/13] PCI: Allow PASID only when ACS enforced on upstreaming path

[Baolu Lu]

On 2022/8/18 21:04, Jason Gunthorpe wrote:
> On Wed, Aug 17, 2022 at 09:20:15AM +0800, Lu Baolu wrote:
> > Some configurations of the PCI fabric will route device originated TLP
> > packets based on the memory addresses. These configurations are
> > incompatible with PASID as the PASID packets form a distinct address
> > space. For instance, any configuration where switches are present
> > without ACS enabled is incompatible.
> >
> > This enhances the pci_enable_pasid() interface by requiring the ACS to
> > support Source Validation, Request Redirection, Completer Redirection,
> > and Upstream Forwarding. This effectively means that devices cannot
> > spoof their requester ID, requests and completions cannot be redirected,
> > and all transactions are forwarded upstream, even as it passes through a
> > bridge where the target device is downstream.
> >
> > Suggested-by: Jason Gunthorpe<jgg@xxxxxxxxxx>
> > Suggested-by: Kevin Tian<kevin.tian@xxxxxxxxx>
> > Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/pci/ats.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> > index c967ad6e2626..0715e48e7973 100644
> > --- a/drivers/pci/ats.c
> > +++ b/drivers/pci/ats.c
> > @@ -382,6 +382,11 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
> >   	if (!pasid)
> >   		return -EINVAL;
> >   
> > +	if (!pci_acs_path_enabled(pdev, NULL,
> > +				  PCI_ACS_SV | PCI_ACS_RR |
> > +				  PCI_ACS_CR | PCI_ACS_UF))
> I think we only need RR and UF here?
>
> Source Validation causes the switch to validate the requestor RID in
> each TLP which has nothing to do with address based routing
>
> Completion Redirect changes how RID routing works, and has nothing to
> do with address based routing.
>
> Yes, both of those are usually set for virtualization scenarios but we
> shouldn't check it here as a basic requirement to enable PASID.

Yes. Here only requires RR and UF.

Best regards,
baolu