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Re: [Xen-devel] [PATCH v2 3/4] sysctl: Add sysctl interface for querying PCI topology



On 01/08/2015 04:50 AM, Jan Beulich wrote:
On 07.01.15 at 18:55, <dario.faggioli@xxxxxxxxxx> wrote:
There probably would not be too serious issues in converting everything
to PXM, or adding duplicates, but I don't see the reason why we should
do such a thing... Perhaps I'm missing what using PXM would actually buy
us?
As long as those node IDs don't get stored persistently for future
use, using them (despite being a Xen internal representation)
ought to be fine. My concern really is that such Xen internals may
easily get mis-used in the tool stack, e.g. assuming that they won't
change across reboots (perhaps after a hypervisor update).

Are PXMs guaranteed to be persistent across firmware upgrades? I don't see anything about this in the APCI spec. The only semi-relevant statement that I found was that PXM values are meaningless (i.e. they are much like cookies).

(FWIW, Linux exposes nodeIDs in the same manner as Xen. In fact, Xen's srat.c appears to be derived from Linux code.)

-boris

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