Intel: 5G ISA: x86: Enumerate AVX512 FP16 CPUID feature flag

mainline inclusion
from mainline-5.11
commit e1b35da5
category: feature
feature: SPR New instructions
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I596EH


CVE: N/A

Intel-SIG: commit e1b35da5 x86: Enumerate AVX512 FP16 CPUID feature flag
Backport for SPR core 5G ISA support.

-------------------------------------

Enumerate AVX512 Half-precision floating point (FP16) CPUID feature
flag. Compared with using FP32, using FP16 cut the number of bits
required for storage in half, reducing the exponent from 8 bits to 5,
and the mantissa from 23 bits to 10. Using FP16 also enables developers
to train and run inference on deep learning models fast when all
precision or magnitude (FP32) is not needed.

A processor supports AVX512 FP16 if CPUID.(EAX=7,ECX=0):EDX[bit 23]
is present. The AVX512 FP16 requires AVX512BW feature be implemented
since the instructions for manipulating 32bit masks are associated with
AVX512BW.

The only in-kernel usage of this is kvm passthrough. The CPU feature
flag is shown as "avx512_fp16" in /proc/cpuinfo.

Signed-off-by: Kyung Min Park <kyung.min.park@intel.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Message-Id: 20201208033441.28207-2-kyung.min.park@intel.com
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Luming Yu <luming.yu@intel.com>