Re: [PATCH 1/2] x86/amd_node: Fix AMD root device caching

Yazen Ghannam
2025-10-21T14:25:14Z

On Tue, Oct 21, 2025 at 04:15:00PM +0200, Borislav Petkov wrote:
> On Tue, Oct 21, 2025 at 09:37:45AM -0400, Yazen Ghannam wrote:
> > It's correct that one of the root devices will be on bus 0x0. But that
> > device will be part of AMD node 0. So we still need to pick a root
> > device for the other, if any, AMD nodes in the system.
> >
> > For example, a system with 2 AMD nodes could have this:
> > Node 0 : 0x00 0x07 0x0e 0x15
> > Node 1 : 0x1c 0x23 0x2a 0x31
>
> Aha, so next question: isn't there a way to figure out which is the *first*
> PCI bus of a AMD node? My gut feeling tells me there should be some info
> somewhere which we can use...
>

Yep, that was one of the goals of the recent rework. I thought the DF
register held that info, but I was mistaken.

I haven't been able to find anything else. We can keep looking, but I
wanted to send out this patch as a fix in the meantime.

Thanks,
Yazen