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

arch/x86/include/asm/cpufeatures.h

@@ -376,6 +376,7 @@
 #define X86_FEATURE_TSXLDTRK		(18*32+16) /* TSX Suspend Load Address Tracking */
 #define X86_FEATURE_PCONFIG		(18*32+18) /* Intel PCONFIG */
 #define X86_FEATURE_ARCH_LBR		(18*32+19) /* Intel ARCH LBR */
+#define X86_FEATURE_AVX512_FP16		(18*32+23) /* AVX512 FP16 */
 #define X86_FEATURE_SPEC_CTRL		(18*32+26) /* "" Speculation Control (IBRS + IBPB) */
 #define X86_FEATURE_INTEL_STIBP		(18*32+27) /* "" Single Thread Indirect Branch Predictors */
 #define X86_FEATURE_FLUSH_L1D		(18*32+28) /* Flush L1D cache */

arch/x86/kernel/cpu/cpuid-deps.c

@@ -69,6 +69,7 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_CQM_MBM_TOTAL,		X86_FEATURE_CQM_LLC   },
 	{ X86_FEATURE_CQM_MBM_LOCAL,		X86_FEATURE_CQM_LLC   },
 	{ X86_FEATURE_AVX512_BF16,		X86_FEATURE_AVX512VL  },
+	{ X86_FEATURE_AVX512_FP16,		X86_FEATURE_AVX512BW  },
 	{ X86_FEATURE_ENQCMD,			X86_FEATURE_XSAVES    },
 	{ X86_FEATURE_PER_THREAD_MBA,		X86_FEATURE_MBA       },
 	{}