Re: [Xen-devel] [PATCH v8 02/17] Add cmpxchg16b support for x86-64

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Wednesday, October 14, 2015 5:46 PM
> To: Wu, Feng <feng.wu@xxxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxx;
> Keir Fraser <keir@xxxxxxx>
> Subject: RE: [PATCH v8 02/17] Add cmpxchg16b support for x86-64
> 
> >>> On 14.10.15 at 11:29, <feng.wu@xxxxxxxxx> wrote:
> > I understand your comments above. My understanding about the gcc
> > online doc is we don't need to add memory clobber when the variable
> > is either an input _or_ output one. However, seems your options is
> > memory clobber can be removed only when it is an input _and_ output
> > one. It would be highly appreciated if you can correct me if I understand
> > the doc incorrectly.
> 
> Yes, I'm pretty convinced you read it wrong: "performs memory
> reads or writes to items other than those listed in the input and
> output operands" means _any_ operation not expressed by the
> ams operands. The two sentence following that actually explain
> this in more detail. IOW - unless your operands correctly express
> _everything_ the assembly instruction(s) do(es), you need a
> clobber (and this is not limited to memory).

Thanks for the clarification. So do you think it is better to send only
this single patch after fixing the issue in your comments, or wait
for the next version of this whole patch set?

Thanks,
Feng

> 
> Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel