Re: [Xen-devel] [for-4.7] x86/emulate: synchronize LOCKed instruction emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.04.16 at 19:23, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 04/26/16 19:03, George Dunlap wrote:
>> On 19/04/16 17:35, Jan Beulich wrote:
>>>>>> Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> 04/19/16 1:01 PM >>>
>>>> I think this might be because the LOCK prefix should guarantee that the
>>>> instruction that follows it has exclusive use of shared memory (for both
>>>> reads and writes) but I might be misreading the docs:
>>>
>>> LOCK definitely has no effect on other than the instruction it gets applied
>>> to.
>> 
>> Sorry I wasn't involved in this discussion -- what was the conclusion here?
>> 
>> FWIW Andy's suggestion of using a stub seemed like the most robust
>> solution, if that could be made to work.
>> 
>> If you're going to submit a patch substantially similar to this one, let
>> me know so I can review the mm bits of the original patch.
> 
> I'm not really sure.
> 
> Regarding this version of the patch, Jan has asked for more information
> on the performance impact, but I'm not sure how to obtain it in a
> rigorous manner.

That was only one half, which Andrew has now answered. The
other was the not understood issue with a later variant you had
tried.

Jan


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