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

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Date:   Mon, 24 Feb 2020 22:31:39 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.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 Mon, Feb 24, 2020 at 11:47:54AM -0500, Steven Rostedt wrote:
> On Mon, 24 Feb 2020 17:34:09 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > Looking at nmi_enter(), that leaves trace_hardirq_enter(), since we know
> > we marked rcu_nmi_enter() as NOKPROBES, per the patches elsewhere in
> > this series.
> 
> Maybe this was addressed already in the series, but I'm just looking at
> Linus's master branch we have:
> 
> #define nmi_enter()                                             \
>         do {                                                    \
>                 arch_nmi_enter();                               \
>                 printk_nmi_enter();                             \
>                 lockdep_off();                                  \
>                 ftrace_nmi_enter();                             \
>                 BUG_ON(in_nmi());                               \
>                 preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \
>                 rcu_nmi_enter();                                \
>                 trace_hardirq_enter();                          \
>         } while (0)
> 
> 
> Just want to confirm that printk_nmi_enter(), lockdep_off(),
> and ftrace_nmi_enter() are all marked fully with NOKPROBE.

*sigh*, right you are, I only looked at notrace, not nokprobe.

In particular the ftrace one is a bit off a mess, let me sort through
that.