lkml.org 
[lkml]   [2019]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH] x86/cpufeatures: Enumerate new AVX512 bfloat16 instructions
On Tue, Jun 11, 2019 at 11:19:20AM -0700, Fenghua Yu wrote:
> 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 */

Yap.

> 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 */

This needs to be (12*32+ 5) if word 12 is going to map leaf
CPUID.(EAX=7,ECX=1):EAX.

At least judging from the arch extensions doc which lists EAX as:

Bits 04-00: Reserved.
Bit 05: AVX512_BF16. Vector Neural Network Instructions supporting BFLOAT16 inputs and conversion instructions from IEEE single precision.
Bits 31-06: Reserved.

> 4. Do other necessary changes to match the new word 11 and word 12.

But split in two patches: first does steps 1+2, second patch adds the
new leaf to word 12.

Thx.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

\
 
 \ /
  Last update: 2019-06-11 21:48    [W:0.119 / U:0.644 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site