Re: [PATCH V4 1/1] Intel Sky Lake-E host root ports check.

Jason Gunthorpe
2022-03-30T19:12:25Z

On Wed, Mar 30, 2022 at 02:10:17PM -0500, Bjorn Helgaas wrote:
> On Wed, Mar 30, 2022 at 12:37:20PM -0300, Jason Gunthorpe wrote:
> > On Wed, Mar 30, 2022 at 05:08:23PM +0300, Shlomo Pongratz wrote:
> > > @@ -350,7 +353,10 @@ static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)
> > >
> > > if (!root)
> > > return NULL;
> > > - if (root->devfn != PCI_DEVFN(0, 0))
> > > +
> > > + /* Is it a host bridge or a root port? */
> >
> > This is a better comment:
> >
> > /* host bridges must have a 0 devfn, but some of the entries in the
> > whilelist are root ports that can have any devfn */
>
> Is this something in the spec or is it just common practice? The PCIe
> spec says very little about "host bridges" and I don't remember
> anything about them having to be devfn 0 or even that they have to be
> materialized as PCI devices.

I think we are relying on common practice here, but I don't know why
this check was added in the first place? Logan?

Jason