Re: [PATCH 1/1] Add AVX512 support for xbzrle_encode_buffer function

[Daniel P . Berrangé]

On Fri, Jul 22, 2022 at 02:23:13AM +0000, Zhao, Zhou wrote:
> 1 we need gcc machined options to tirgger gcc enable SIMD
> instructions(https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html).
> Or it will trigger a compile error. This is the reason why we
> change the config file.

Take a look at util/bufferiszero.c   - that uses '#pragma GCC target'
to selectively change the compule target of individual functions.

This is what is njeeded here, because most distros are going to
compile QEMU with a very old x86_64 baseline, never turn on avx512
for the whole QEMU build. It needs to be very selective to make
it usable for typical deployments.

With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|