Re: [PATCH] i386: Add syscall to enable AMX for latest kernels

[Uros Bizjak <ubizjak@gmail.com>]

On Mon, Jun 20, 2022 at 10:04 AM Haochen Jiang <haochen.jiang@intel.com> wrote:
>
> From: "Jiang, Haochen" <haochen.jiang@intel.com>
>
> Hi all,
>
> We need syscall to enable AMX for kernels>=5.4. It is missing in current
> amx tests, which will cause test fail.

So this new code is only valid for linux & co?

Uros.

>
> This patch aims to add them to fix this bug.
>
> BRs,
> Haochen
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/i386/amx-check.h (request_perm_xtile_data):
>         New function to check if AMX is usable and enable AMX.
>         (main): Run test if AMX is usable.
> ---
>  gcc/testsuite/gcc.target/i386/amx-check.h | 24 +++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/gcc/testsuite/gcc.target/i386/amx-check.h b/gcc/testsuite/gcc.target/i386/amx-check.h
> index 434b0e59703..92ed8669304 100644
> --- a/gcc/testsuite/gcc.target/i386/amx-check.h
> +++ b/gcc/testsuite/gcc.target/i386/amx-check.h
> @@ -4,11 +4,22 @@
>  #include <stdlib.h>
>  #include <string.h>
>  #include <stdint.h>
> +#include <unistd.h>
> +#include <sys/syscall.h>
>  #ifdef DEBUG
>  #include <stdio.h>
>  #endif
>  #include "cpuid.h"
>
> +#define XFEATURE_XTILECFG      17
> +#define XFEATURE_XTILEDATA     18
> +#define XFEATURE_MASK_XTILECFG (1 << XFEATURE_XTILECFG)
> +#define XFEATURE_MASK_XTILEDATA        (1 << XFEATURE_XTILEDATA)
> +#define XFEATURE_MASK_XTILE    (XFEATURE_MASK_XTILECFG | XFEATURE_MASK_XTILEDATA)
> +
> +#define ARCH_GET_XCOMP_PERM    0x1022
> +#define ARCH_REQ_XCOMP_PERM    0x1023
> +
>  /* TODO: The tmm emulation is temporary for current
>     AMX implementation with no tmm regclass, should
>     be changed in the future. */
> @@ -44,6 +55,18 @@ typedef struct __tile
>  /* Stride (colum width in byte) used for tileload/store */
>  #define _STRIDE 64
>
> +/* We need syscall to use amx functions */
> +int request_perm_xtile_data()
> +{
> +  unsigned long bitmask;
> +
> +  if (syscall (SYS_arch_prctl, ARCH_REQ_XCOMP_PERM, XFEATURE_XTILEDATA) ||
> +      syscall (SYS_arch_prctl, ARCH_GET_XCOMP_PERM, &bitmask))
> +    return 0;
> +
> +  return (bitmask & XFEATURE_MASK_XTILE) != 0;
> +}
> +
>  /* Initialize tile config by setting all tmm size to 16x64 */
>  void init_tile_config (__tilecfg_u *dst)
>  {
> @@ -186,6 +209,7 @@ main ()
>  #ifdef AMX_BF16
>        && __builtin_cpu_supports ("amx-bf16")
>  #endif
> +      && request_perm_xtile_data ()
>        )
>      {
>        DO_TEST ();
> --
> 2.18.2
>