linux-kernel - Re: [PATCH 0/6] x86/fpu: don't abuse x86_task_fpu(PF_USER_WORKER) in .regset

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Message-ID: <f8aaa8a3-e4aa-4958-a147-9a40385ebd8d@intel.com>
Date: Fri, 15 Aug 2025 09:32:00 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: Oleg Nesterov <oleg@...hat.com>, Dave Hansen <dave.hansen@...el.com>
CC: Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>, Jens Axboe
	<axboe@...nel.dk>, Peter Zijlstra <peterz@...radead.org>, Rick Edgecombe
	<rick.p.edgecombe@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
	<linux-kernel@...r.kernel.org>, <x86@...nel.org>, Mark Brown
	<broonie@...nel.org>
Subject: Re: [PATCH 0/6] x86/fpu: don't abuse x86_task_fpu(PF_USER_WORKER) in
 .regset_get() paths

On 8/15/2025 9:02 AM, Oleg Nesterov wrote:
>>> Dave, Sohil, what do you think?

Thank you for doing this series.

I think it would be useful to categorize the impact of the "abuse" in
the cover letter. Is it going to cause kernel crashes, userspace crashes
or just incorrect reporting?

Are there any "must do" fixes that need to be backported in comparison
with the "good to have" optimizations? I am wondering if it might be
possible to structure the series that way to make the separation clear.

> I agree about the cover letter, but what else do you think the changelog
> in 1/6 could say? ;)
> 

For folks like me who are barely familiar with the FPU code, some
additional context or reasoning would be surely be useful.

For example, I don't know why PKRU needs to be passed separately. I know
there is some history there but a line or two in the changelog might help.