linux-kernel - Re: [PATCH v2 1/1] Documentation/x86: Add the AMX enabling example

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Message-ID: <5c67d453-a162-b61d-4a27-c854f1ef3587@intel.com>
Date:   Thu, 30 Jun 2022 08:26:54 -0700
From:   "Chang S. Bae" <chang.seok.bae@...el.com>
To:     "Luck, Tony" <tony.luck@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
CC:     "corbet@....net" <corbet@....net>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-man@...r.kernel.org" <linux-man@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/1] Documentation/x86: Add the AMX enabling example

On 6/29/2022 4:30 PM, Luck, Tony wrote:
> +        #define ARCH_GET_XCOMP_SUPP  0x1021
> +
> +        #define XFEATURE_XTILECFG    17
> +        #define XFEATURE_XTILEDATA   18
> 
> What's the long-term plan for these #defines?  I see that ARCH_GET_XCOMP_SUPP
> is in arch/x86/include/uapi/asm/prctl.h ... so eventually that will show up in distribution
> /usr/include/asm/prctl.h courtesy of a glibc update.
> 
> But the XFEATURE bits aren't in a "uapi" file. They are an "enum" in:
> 
> arch/x86/include/asm/fpu/types.h
> 
> How will that get to /usr/include?

Perhaps I can think of something like this for AMX state:

diff --git a/arch/x86/include/uapi/asm/prctl.h 
b/arch/x86/include/uapi/asm/prctl.h
index 500b96e71f18..08b6c9155b8a 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -16,6 +16,9 @@
  #define ARCH_GET_XCOMP_GUEST_PERM      0x1024
  #define ARCH_REQ_XCOMP_GUEST_PERM      0x1025

+#define ARCH_XCOMP_XTILECFG            17
+#define ARCH_XCOMP_XTILEDATA           18
+
  #define ARCH_MAP_VDSO_X32              0x2001
  #define ARCH_MAP_VDSO_32               0x2002
  #define ARCH_MAP_VDSO_64               0x2003

But these state components are architectural. While this can help 
userspace anyway, saying "XSTATE component" here and on the man-page is 
probably it as they are already defined in the x86 spec.

Thanks,
Chang