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Re: [PATCH] X86-64: Add _dl_runtime_resolve_avx[512]_opt [BZ #20508]

On 10/04/2016 08:13 PM, Adhemerval Zanella wrote:

I think 2.24 it is ok since it contains the BZ#20139 fix already.  For 2.23,
although it was not really explicit in NEWS, AVX512 is suppose to be supported
in a set of different implementation (memmove/memcpy/libmvec).  However my
understanding of this issue is limited to be a performance one, so I do not
see a pressing matter to change a release requirements for such change.
As far as I understand it, the issue is that the trampoline writes to the SSE/AVX/AVX2 registers, which clears the AVX-512F bits (which are not saved by the trampoline).
Intel introduced AVX512F in such a manner that you have to upgrade kernel and userspace in lock-step, which is of course unrealistic. 

Florian
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