On Mon, Jun 10, 2019 at 09:20:26PM +0200, Borislav Petkov wrote: > On Mon, Jun 10, 2019 at 10:02:38AM -0700, Fenghua Yu wrote: > > AVX512 Vector Neural Network Instructions (VNNI) in Intel Deep Learning > > Boost support bfloat16 format (BF16). BF16 is a short version of FP32 and > > has several advantages over FP16. BF16 offers more than enough range for > > deep learning training tasks and doesn't need to handle hardware exception > > as this is a performance optimization. FP32 accumulation after the > > multiply is essential to achieve sufficient numerical behavior on an > > application level. > > > > AVX512 bfloat16 instructions can be enumerated by: > > CPUID.(EAX=7,ECX=1):EAX[bit 5] AVX512_BF16 > > > > Detailed information of the CPUID bit and AVX512 bfloat16 instructions > > can be found in the latest Intel Architecture Instruction Set Extensions > > and Future Features Programming Reference. > > > > Signed-off-by: Fenghua Yu <fenghua...@intel.com> > > --- > > > > Since split lock feature (to-be-upstreamed) occupies the last bit > > of word 7, need to create a new word 19 to host AVX512_BF16 and other > > future features. > > Is CPUID.(EAX=7,ECX=1):EAX going to contain only feature bits? If so, > just make it a proper feature word instead of a linux-specific one.
AFAICT, there will be more features in the EAX register in the future. Ok. I will use a feature word for CPUID.(EAX=7,ECX=1):EAX. > > Also, while on the subject, you can recycle word 11 > > /* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:0 (EDX), word 11 */ > #define X86_FEATURE_CQM_LLC (11*32+ 1) /* LLC QoS if 1 */ > > and move it to scattered as it is a complete waste. Word 12 too, for > that matter. But do that in separate patches. So can I re-organize word 11 and 12 as follows? 1. Change word 11 to host scattered features. 2. Move the previos features in word 11 and word 12 to word 11: /* * Extended auxiliary flags: Linux defined - For features scattered in various * CPUID levels and sub-leaves like CPUID level 7 and sub-leaf 1, etc, word 19. */ #define X86_FEATURE_CQM_LLC (11*32+ 0) /* LLC QoS if 1 */ #define X86_FEATURE_CQM_OCCUP_LLC (11*32+ 1) /* LLC occupancy monitoring */ #define X86_FEATURE_CQM_MBM_TOTAL (11*32+ 2) /* LLC Total MBM monitoring */ #define X86_FEATURE_CQM_MBM_LOCAL (11*32+ 3) /* LLC Local MBM monitoring */ 3. Change word 12 to host CPUID.(EAX=7,ECX=1):EAX: /* Intel-defined CPU features, CPUID level 0x7:1 (EAX), word 12 */ #define X86_FEATURE_AVX512_BF16 (12*32+ 0) /* BFLOAT16 instructions */ 4. Do other necessary changes to match the new word 11 and word 12. Thanks. -Fenghua
