linux-kernel - Re: [patch V4 part 3 01/29] x86/traps: Mark fixup_bad

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Date:   Tue, 12 May 2020 21:51:08 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 3 01/29] x86/traps: Mark fixup_bad_iret()
 noinstr

On Fri, 8 May 2020 17:39:00 -0700
Andy Lutomirski <luto@...nel.org> wrote:

> On Tue, May 5, 2020 at 7:15 AM Thomas Gleixner <tglx@...utronix.de> wrote:
> >
> > This is called from deep entry ASM in a situation where instrumentation
> > will cause more harm than providing useful information.
> >  
> 
> Acked-by: Andy Lutomirski <luto@...nel.org>
> 
> Maybe add to changelog:
> 
> Switch from memmove() to memcpy() because memmove() can't be called
> from noinstr code.

Yes please, because I was about to say that there was changes that
didn't seem to fit the change log.

I would also add a comment in the code saying that we need the temp
variable to use memcpy as memmove can't be used in noinstr code.

-- Steve