linux-kernel - Re: [tip: x86/fpu] x86/fpu/xstate: Define new functions for clearing fpregs and xstates

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Date:   Thu, 1 Dec 2022 06:04:45 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Ivan Zahariev <famzah@...soft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Yu, Yu-cheng" <yu-cheng.yu@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     linux-tip-commits@...r.kernel.org,
        Fenghua Yu <fenghua.yu@...el.com>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>, x86 <x86@...nel.org>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>
Subject: Re: [tip: x86/fpu] x86/fpu/xstate: Define new functions for clearing
 fpregs and xstates

On 12/1/22 04:58, Ivan Zahariev wrote:
> We are running 5.15.75 (LTS) but the problem started when we upgraded
> from 5.15.31 to 5.15.59 and is present ever since. I erroneously said
> that it's present into every 5.15.
> I didn't do my homework well and blamed the commit by Yu-cheng Yu. 
> But this commit never landed into 5.15, nor the fix commit that you>
> referred. There are no functions fpu__clear_all(), 
> copy_init_fpstate_to_fpregs(), copy_user_to_xstate() anywhere in the>
> sources of 5.15.75 or 5.15.31, so the 5.15 kernel is running with a 
> different FPU implementation.
It's also possible that the Ubuntu kernel folks pulled some FPU patches
into their 5.15 kernel from later upstream kernels, which is adding to
the confusion.  I think there may have been some effort to backport the
AMX work.

You might want to file a bug report with the Ubuntu folks.