Messages in this thread | | | Date | Thu, 30 Jun 2022 10:03:26 +0700 | Subject | Re: [PATCH v2 1/1] Documentation/x86: Add the AMX enabling example | From | Bagas Sanjaya <> |
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On 6/30/22 05:42, Chang S. Bae wrote: > Explain steps to enable the dynamic feature with a code example. > > Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> > Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> > Cc: linux-doc@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > --- > Changes from v1: > * Update the description without mentioning CPUID & XGETBV (Dave Hansen). > --- > Documentation/x86/xstate.rst | 42 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/Documentation/x86/xstate.rst b/Documentation/x86/xstate.rst > index 5cec7fb558d6..c439901419fb 100644 > --- a/Documentation/x86/xstate.rst > +++ b/Documentation/x86/xstate.rst > @@ -64,6 +64,48 @@ the handler allocates a larger xstate buffer for the task so the large > state can be context switched. In the unlikely cases that the allocation > fails, the kernel sends SIGSEGV. > > +AMX TILE_DATA enabling example > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +The following steps dynamically enable TILE_DATA: > +
This should be "Below is the example of how userspace applications enable TILE_DATA dynamically:"
> + 1. An application first needs to determine the feature support:: > +
Better say "The application first needs to query the kernel for AMX support".
> + #include <asm/prctl.h> > + #include <sys/syscall.h> > + #include <stdio.h> > + #include <unistd.h> > + > + #define ARCH_GET_XCOMP_SUPP 0x1021 > + > + #define XFEATURE_XTILECFG 17 > + #define XFEATURE_XTILEDATA 18 > + #define XFEATURE_MASK_XTILE ((1 << XFEATURE_XTILECFG) | (1 << XFEATURE_XTILEDATA)) > + > + unsigned long features; > + long rc; > + > + ... > + > + rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_SUPP, &features); > + > + if (!rc && (features & XFEATURE_MASK_XTILE) == XFEATURE_MASK_XTILE) > + printf("AMX is available.\n"); > + > + 2. After determining support for AMX, an application must explicitly ask > + permission to use it:: > +
Shorter is "After that,..."
> + #define ARCH_REQ_XCOMP_PERM 0x1023 > + > + ... > + > + rc = syscall(SYS_arch_prctl, ARCH_REQ_XCOMP_PERM, XFEATURE_XTILEDATA); > + > + if (!rc) > + printf("AMX is ready for use.\n"); > + > +Note this example does not include the sigaltstack preparation. > +
I guess "application" here means userspace application, right?
-- An old man doll... just what I always wanted! - Clara
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