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

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Message-ID: <71c0b3b3-f9a7-378d-89bb-3035a7b0b494@intel.com>
Date:   Thu, 30 Jun 2022 09:17:26 -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 6/30/2022 9:07 AM, Luck, Tony wrote:
>> 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.
> 
> An application writer can't use:
> 
> # include {x86 spec}"
> 
> to get these values ... if applications need them to find out if AMX is present,
> and to enable it, then they need an API.

Yeah, you're right.

> 
> Maybe your example code should just be a library routine? So application writers
> can just do:
> 
> if (!intel_amx_enable()) {
> error message, or fall back to non-AMX implementation
> }
> 
> without having to worry about those #defines.

I guess we cannot assume this. Given the arch_prctl() options, they can 
do this by themselves.

Let me include those defines on the next version.

Thanks,
Chang