linux-kernel - Re: [PATCH v4 05/27] x86: Replace ist_enter() with nmi

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Date:   Fri, 21 Feb 2020 21:22:46 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Greg KH <gregkh@...uxfoundation.org>, gustavo@...eddedor.com,
        Thomas Gleixner <tglx@...utronix.de>, paulmck@...nel.org,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Tony Luck <tony.luck@...el.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH v4 05/27] x86: Replace ist_enter() with nmi_enter()

On Fri, Feb 21, 2020 at 11:05:36AM -0800, Andy Lutomirski wrote:

> > -       /*
> > -        * Use ist_enter despite the fact that we don't use an IST stack.
> > -        * We can be called from a kprobe in non-CONTEXT_KERNEL kernel
> > -        * mode or even during context tracking state changes.
> > -        *
> > -        * This means that we can't schedule.  That's okay.
> > -        */
> > -       ist_enter(regs);
> > +       nmi_enter();
> 
> I agree with the change, but some commentary might be nice.  Maybe
> copy from here:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/idtentry&id=061eaa900b4f63601ab6381ab431fcef8dfd84be

Fair enough; I'll add something to #DB and #BP for that.