linux-kernel - Re: [PATCH RFC v1 00/11] x86: Support Intel Advanced Performance Extensions

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Message-ID: <afa6abf6-83d8-45d1-9e05-64e95680e7c8@intel.com>
Date: Thu, 27 Feb 2025 19:10:51 -0800
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: Dave Hansen <dave.hansen@...el.com>, Ingo Molnar <mingo@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>, "Linus
 Torvalds" <torvalds@...ux-foundation.org>
Subject: Re: [PATCH RFC v1 00/11] x86: Support Intel Advanced Performance
 Extensions

On 2/27/2025 11:36 AM, Dave Hansen wrote:
> On 2/27/25 11:15, Ingo Molnar wrote:
>>> by userspace applications, with no intended use in kernel mode. More
>>                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> details on its use cases can be found in the published documentation [1].
>> I strongly suspect this won't remain so, unless there's some horrible
>> ISA limitation or other quirk that makes APX unsuitable for kernel use.
> 
> I think Chang was trying to say that this series is completely focused
> on userspace AMX and basically ignores the idea of using it in the kernel.
> 
> That said, we honestly talk all the time about using it in the kernel. A
> kernel compiled to use APX everywhere obviously won't run on older CPUs
> but it _should_ have some really nice advantages. I completely expect
> the kernel to be able to be compiled to use APX at _some_ point.

Yes, exactly. My primary intent was to clarify that this posting is for 
supporting userspace APX usage. At the same time, I don’t want this to 
imply little or no potential for in-kernel use.

Thanks,
Chang