[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 11 Oct 2011 00:15:48 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: Borislav Petkov <bp@...64.org>
CC: "tj@...nel.org" <tj@...nel.org>,
Alan Stern <stern@...land.harvard.edu>,
"rjw@...k.pl" <rjw@...k.pl>, "pavel@....cz" <pavel@....cz>,
"len.brown@...el.com" <len.brown@...el.com>,
"mingo@...e.hu" <mingo@...e.hu>,
"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"suresh.b.siddha@...el.com" <suresh.b.siddha@...el.com>,
"lucas.demarchi@...fusion.mobi" <lucas.demarchi@...fusion.mobi>,
"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
"rdunlap@...otime.net" <rdunlap@...otime.net>,
"vatsa@...ux.vnet.ibm.com" <vatsa@...ux.vnet.ibm.com>,
"ashok.raj@...el.com" <ashok.raj@...el.com>,
"tigran@...azian.fsnet.co.uk" <tigran@...azian.fsnet.co.uk>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"hpa@...or.com" <hpa@...or.com>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v2 0/3] Freezer, CPU hotplug, x86 Microcode: Fix task
freezing failures
On 10/11/2011 12:04 AM, Borislav Petkov wrote:
> Hi Tejun,
>
> On Mon, Oct 10, 2011 at 02:08:48PM -0400, tj@...nel.org wrote:
>> Maybe I'm confused but is that patch correct for actual CPU hotplug
>> case? If not, what's the point in doing that? What are we gonna do
>> after six month some people come up with "CPU hotplug fails to load
>> new microcode for the new CPU"?
>
[...]
>
>> If somebody is sure that microcode don't need to be changed once
>> loaded, then all's good and dandy but that's not the case here, right?
>
> Well, basically the current situation didn't change the ucode - it
> simply reloaded the same image from before going offline.
>
> See, there's this another problem with what we have right now: imagine
> you've just updated the ucode image on disk and offline only a subset of
> the cores. Then you online them again and they now get the newer ucode
> image while the others still run the old ucode. This could explode or
> could not, one thing's for sure: all bets are off. If we don't reload it
> on hotplug, we're fine - only module reload triggers the ucode update in
> a fairly synchronized manner.
>
This one makes a lot of sense to me. I hadn't thought of it before.
>> If you want to optimize away microcode unloading during
>> suspend/resume, the RTTD is doing revalidation / reload during
>> CPU_ONLINE as necessary.
>
> see above.
>
>> If this use case doesn't really matter too much to anyone, just
>> leaving it alone would be better than adding band aid which can lead
>> to very obscure issues down the road (oooh, that microcode shouldn't
>> have been loaded to that cpu).
>
> I'd like to actually hear someone justify such a requirement.
>
> I hope I'm making some sense here.
>
--
Regards,
Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Linux Technology Center,
IBM India Systems and Technology Lab
--
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/
Powered by blists - more mailing lists