Re: [PATCH v2 00/10] x86: support AVX512-FP16

[Jan Beulich <jbeulich@xxxxxxxx>]

On 22.05.2023 18:25, Andrew Cooper wrote:
> On 03/04/2023 3:56 pm, Jan Beulich wrote:
>> While I (quite obviously) don't have any suitable hardware, Intel's
>> SDE allows testing the implementation. And since there's no new
>> state (registers) associated with this ISA extension, this should
>> suffice for integration.
> 
> I've given this a spin on a Sapphire Rapids system.
> 
> Relevant (AFAICT) bits of the log:
> 
> Testing vfpclasspsz $0x46,64(%edx),%k2...okay
> Testing vfpclassphz $0x46,128(%ecx),%k3...okay
> ...
> Testing avx512_fp16/all disp8 handling...okay
> Testing avx512_fp16/128 disp8 handling...okay
> ...
> Testing AVX512_FP16 f16 scal native execution...okay
> Testing AVX512_FP16 f16 scal 64-bit code sequence...okay
> Testing AVX512_FP16 f16 scal 32-bit code sequence...okay
> Testing AVX512_FP16 f16x32 native execution...okay
> Testing AVX512_FP16 f16x32 64-bit code sequence...okay
> Testing AVX512_FP16 f16x32 32-bit code sequence...okay
> Testing AVX512_FP16+VL f16x8 native execution...okay
> Testing AVX512_FP16+VL f16x8 64-bit code sequence...okay
> Testing AVX512_FP16+VL f16x8 32-bit code sequence...okay
> Testing AVX512_FP16+VL f16x16 native execution...okay
> Testing AVX512_FP16+VL f16x16 64-bit code sequence...okay
> Testing AVX512_FP16+VL f16x16 32-bit code sequence...okay
> 
> and it exits zero, so everything seems fine.
> 
> 
> One thing however, this series ups the minimum GCC version required to
> build the emulator at all:
> 
> make: Entering directory '/local/xen.git/tools/tests/x86_emulator'
> gcc: error: unrecognized command-line option ‘-mavx512fp16’; did you
> mean ‘-mavx512bf16’?
> Makefile:121: Test harness not built, use newer compiler than "gcc"
> (version 10) and an "{evex}" capable assembler
> 
> and I'm not sure we want to do this.  When upping the version of GCC but
> leaving binutils as-was does lead to a build of the harness without
> AVX512-FP16 active, which is the preferred behaviour here.

Well, this series on its own does, but I did notice the issue already.
Hence "x86emul: rework compiler probing in the test harness" [1].

Jan

[1] https://lists.xen.org/archives/html/xen-devel/2023-03/msg00123.html