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Date:   Thu, 19 Nov 2020 21:08:03 -0800
From:   Andy Lutomirski <>
To:     "Chang S. Bae" <>
Cc:     Thomas Gleixner <>,
        Ingo Molnar <>, Borislav Petkov <>,
        Andrew Lutomirski <>, X86 ML <>,
        Len Brown <>,
        Dave Hansen <>,
        "Liu, Jing2" <>,
        "Ravi V. Shankar" <>,
        LKML <>
Subject: Re: [PATCH v2 14/22] x86/fpu/xstate: Inherit dynamic user state when
 used in the parent

On Thu, Nov 19, 2020 at 3:37 PM Chang S. Bae <> wrote:
> When a new task is created, the kernel copies all the states from the
> parent. If the parent already has any dynamic user state in use, the new
> task has to expand the XSAVE buffer to save them. Also, disable the
> associated first-use fault.

This seems like a mistake.  If init uses AMX for some misguided
reason, ever task on the whole system will end up with AMX state

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