Re: [Xen-devel] [PATCH] x86emul: support clzero

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.09.15 at 10:02, <JBeulich@xxxxxxxx> wrote:
>>>> On 23.09.15 at 19:37, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 22/09/15 14:06, Jan Beulich wrote:
>>> ... in anticipation of this possibly going to get used by guests for
>>> basic thinks like memset() or clearing or pages.
>>>
>>> Since the emulation doesn't use clzero itself, checking the guest's
>>> CPUID for the feature to be exposed is (intentionally) being avoided
>>> here. All that's required is sensible guest side data for the clflush
>>> line size.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> 
>> Where have you found this instruction?  Googling, I have found a
>> presentation talking about it being new in the new AMD Zen cores, but I
>> still can't locate any technical documentation on the matter.
> 
> Sadly no technical documentation so far, despite me pinging for it
> after the respective binutils patch
> (https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=029f 
> 3522619e8b77a7b848be23f4c13e50087d8b)
> got posted and went in.

Sherry,

any chance you could help out here making this make some forward
progress?

Jan


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