Re: [Xen-devel] Re: [PATCH] xen: drop anti-dependency on X86_VISWS

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

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@xxxxxxxx> 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.



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