Re: [PATCH V7 5/9] PCI/IOV: Enable 10-Bit tag support for PCIe VF devices

Bjorn Helgaas
2021-08-06T22:59:20Z

On Thu, Aug 05, 2021 at 04:03:58PM +0800, Dongdong Liu wrote:
>
> On 2021/8/5 7:29, Bjorn Helgaas wrote:
> > On Wed, Aug 04, 2021 at 09:47:04PM +0800, Dongdong Liu wrote:
> > > Enable VF 10-Bit Tag Requester when it's upstream component support
> > > 10-bit Tag Completer.
> >
> > I think "upstream component" here means the PF, doesn't it? I don't
> > think the PF is really an *upstream* component; there's no routing
> > like with a switch.
>
> I want to say the switch and root port devices that support 10-Bit
> Tag Completer. Sure, VF also needs to have 10-bit Tag Requester
> Supported capability.

OK. IIUC we're not talking about P2PDMA here; we're talking about
regular DMA to host memory, which means I *think* only the Root Port
is important, since it is the completer for DMA to host memory. We're
not talking about P2PDMA to a switch BAR, where the switch would be
the completer.