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Date:   Sun, 10 May 2020 10:46:25 +0200
From:   Borislav Petkov <>
To:     Yu-cheng Yu <>
        "H. Peter Anvin" <>,
        Thomas Gleixner <>,
        Ingo Molnar <>,
        Dave Hansen <>,
        Tony Luck <>,
        Andy Lutomirski <>,
        Rik van Riel <>,
        "Ravi V. Shankar" <>,
        Sebastian Andrzej Siewior <>,
        Fenghua Yu <>,
        Peter Zijlstra <>
Subject: Re: [PATCH v3 09/10] x86/fpu/xstate: Preserve supervisor states for
 slow path of __fpu__restore_sig()

On Sat, Mar 28, 2020 at 09:43:06AM -0700, Yu-cheng Yu wrote:
> The signal return code is responsible for taking an XSAVE buffer present
> in user memory and loading it into the hardware registers.  This
> operation only affects user XSAVE state and never affects supervisor state.
> The fast path through this code simply points XRSTOR directly at the
> user buffer.  However, due to page faults, this XRSTOR can fail.  If it

"However, since user memory is not guaranteed to be always mapped, ... "

> fails, the signal return code falls back to a slow path which can
> tolerate page faults.
> That slow path copies the xfeatures one by one out of the user buffer
> into the task's fpu state area.  However, by being in a context where it
> can handle page faults, the code can also schedule.  That exposes us to
Pls use passive voice in your commit message: no "we" or "I", etc, and
describe your changes in imperative mood.

Fix this in all your commit messages pls.


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