Re: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values o

xen-devel

Re: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs u

To:	Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Subject:	Re: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits
From:	Keir Fraser <keir.xen@xxxxxxxxx>
Date:	Fri, 15 Apr 2011 18:28:09 +0100
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx, "winston.l.wang" <winston.l.wang@xxxxxxxxx>
Delivery-date:	Fri, 15 Apr 2011 10:28:44 -0700
Dkim-signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:user-agent:date:subject:from:to:cc:message-id :thread-topic:thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; bh=eSy0VMy/aTtd/CFJnK4QVdoC1LACKdyFc49T13puz4k=; b=vR4+NrlBeMj8uGIrg3sJDCUswA8F2D7FWDRS2veA0tmynzcbDwGmnt7n6YGGka4GDM CKroCUs55GvRD3SUoEvchhWCe4FOgk8wS/4oXczdehInzBs59bzPAc+LT/WUKk7/7/DW DgUDydLopw2Hr8dsI898/bLIVxExbYPRLO9GM=
Domainkey-signature:	a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=user-agent:date:subject:from:to:cc:message-id:thread-topic :thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; b=oo6IohgTvjdDAWJPE0NZJpjNqJQ2nGEBDDDvN4E7GC7H0kFnV6RVt6bd+S/BQhdmnk cZEeDuUuVWtmhDscEx1Fi8chIznDc2XDL12ihFZL/J6JU0Zz2uTDTiF31u5mgR8bIm6+ eX4sS067F/EdnkP8+q++kJ+zKZ5oEO3I/Vm7A=
Envelope-to:	www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to:	<e1e889c5-4d60-4162-a7d2-04423d8bbea9@default>
List-help:	<mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id:	Xen developer discussion <xen-devel.lists.xensource.com>
List-post:	<mailto:xen-devel@lists.xensource.com>
List-subscribe:	<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe:	<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender:	xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index:	Acv7knzuD8qiaBaO3U+XOv4orqRz1w==
Thread-topic:	[Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits
User-agent:	Microsoft-Entourage/12.28.0.101117

On 15/04/2011 15:34, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>>> Agreed.  In fact, maybe it should be asserted in write_tsc?
>> 
>> We still write_tsc on CPU physical hot-add.
> 
> Hmmm... IIRC the testing that Intel was doing for hot-add was
> not for processors that were actually electrically hot-plugged
> but only for processors that were powered-on at the same
> time as all other processors but left offline until needed
> (e.g. for capacity-on-demand).  For this situation, writing
> to tsc is still the wrong approach.  I don't think we finished
> the discussion about electrically hot-plugged processors
> because they didn't exist... don't know if they do yet either.
> IIRC I had proposed an unnamed boot parameter that said
> "this machine may add unsynchronized processors post-boot"
> and disallow hot-add processors if not specified (or if
> not specified AND a run-time check of a hot-add processor
> shows non-synchronization).

Well, I think the case I'm thinking of is electrical hot-plug. Not sure.
Either way I doubt anyone is actually using the feature.

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread]

Current Thread

[Next in Thread>

Previous by Date:

Re: [Xen-devel] Which kernel for dom0 with pv_ops, Pasi Kärkkäinen

Next by Date:

[Xen-devel] [xen-unstable test] 6854: regressions - FAIL, xen . org

Previous by Thread:

RE: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits, Dan Magenheimer

Next by Thread:

Re: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits, Jan Beulich

Indexes:

[Date] [Thread] [Top] [All Lists]

WARNING - OLD ARCHIVES

xen-devel

Re: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs u