linux-kernel - Re: [PATCH] x86: add /proc/cpuinfo/physical id quirks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 14 Aug 2009 13:27:30 -0600
From:	Alex Chiang <achiang@...com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	"hpa@...or.com" <hpa@...or.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: add /proc/cpuinfo/physical id quirks

* Suresh Siddha <suresh.b.siddha@...el.com>:
> On Fri, 2009-08-14 at 09:36 -0700, Alex Chiang wrote:
> > As systems become larger and more complex, it is not always possible
> > to assume that an APIC ID maps directly to a given physical slot.
> > 
> > From a UI point-of-view, it's nice if the 'physical id' field in
> > /proc/cpuinfo matches the silk-screening or labelling on the system
> > chassis.
> > 
> > Add a quirk that allows oddball platforms to ensure that what the kernel
> > displays in /proc/cpuinfo matches the physical reality.
> 
> Alex, Does it makes sense to add a new entry in /proc/cpuinfo rather
> than overloading the 'physical id' by modifying phys_proc_id.

Hm, I'm not entirely sure about that, for two reasons.

First (and this is the weaker reason), I'd prefer not to keep
adding new fields to /proc/cpuinfo if we can help it, as it just
makes for a continually more complicated ABI/API for userspace.

Second, I guess I'm not sure what else 'physical id' /should/
represent. I'm willing to be corrected on this point, so if I'm
wrong, just call it simple ignorance. :)

> That way, even if there is a mis-match between the bios and the
> OS fixup tables, we won't screw up other topology setup etc in
> the kernel that are dependent on the phys_proc_id.

My quick grep earlier led me to believe that as long as the
phys_proc_ids were /consistent/ then it didn't seem to matter
what their /values/ were.

In other words, my patch simply says, "all cores that had
phys_proc_id X now have phys_proc_id Y". All the cores on a
physical package have identical phys_proc_ids, and cores on a
different physical package do /not/ collide.

But again, that just might be my ignorance again. If we do indeed
care about the values of phys_proc_ids, please let me know and
I'd be happy to rework the patch.

Thanks.

/ac

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/