From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <Ian.Campbell@eu.citrix.com>
Subject: Re: Re: [PATCH] xen: drop anti-dependency on X86_VISWS
Date: Sat, 9 Apr 2011 11:34:52 +0100
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To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: "randy.dunlap@oracle.com" <randy.dunlap@oracle.com>, Jeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com>, "eric.dumazet@gmail.com" <eric.dumazet@gmail.com>, "konrad.wilk@oracle.com" <konrad.wilk@oracle.com>, Miller <davem@davemloft.net>, Jan Beulich <JBeulich@novell.com>, "virtualization@lists.linux-foundation.org" <virtualization@lists.linux-foundation.org>, "mingo@redhat.com" <mingo@redhat.com>, "hpa@zytor.com" <hpa@zytor.com>, "tglx@linutronix.de" <tglx@linutronix.de>, "mirq-linux@rere.qmqm.pl" <mirq-linux@rere.qmqm.pl>, "pazke@donpac.ru" <pazke@donpac.ru>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, David
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On Fri, 2011-04-08 at 11:24 -0700, Jeremy Fitzhardinge wrote:
> On 04/08/2011 08:42 AM, Jan Beulich wrote:
> >>>> On 08.04.11 at 17:25, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> >> On 04/07/2011 11:38 PM, Ian Campbell wrote:
> >>> Is there any downside to this patch (is X86_CMPXCHG in the same sort of
> >>> boat?)
> >> Only if we don't use cmpxchg in shared memory with other domains or the
> >> hypervisor.  (I don't think it will dynamically switch between real and
> >> emulated cmpxchg depending on availability.)

We do use cmpxchg in the grant table code at least (actually,
sync_cmpxchng in that case).

> > Actually it does - see the "#ifndef CONFIG_X86_CMPXCHG" section
> > in asm/cmpxchg_32.h.
> 
> Hm, OK.  Still, I'm happiest with that dependency in case someone
> knobbles the cpu to exclude cmpxchg and breaks things.

Dropping the TSC patch is sensible though?

Ian.