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Date:   Wed, 26 Feb 2020 19:59:45 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Borislav Petkov <bp@alien8.de>
Cc:     Andy Lutomirski <luto@amacapital.net>,
        Andy Lutomirski <luto@kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Brian Gerst <brgerst@gmail.com>,
        Juergen Gross <JGross@suse.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>
Subject: Re: [patch 02/10] x86/mce: Disable tracing and kprobes on
 do_machine_check()
Message-ID: <20200226185945.GC18400@hirez.programming.kicks-ass.net>
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 <C06C32B4-BD69-4287-BC67-C3E225061A46@amacapital.net>
 <20200226184237.GB16756@zn.tnic>
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On Wed, Feb 26, 2020 at 07:42:37PM +0100, Borislav Petkov wrote:
> On Wed, Feb 26, 2020 at 09:28:51AM -0800, Andy Lutomirski wrote:
> > > It entirely depends on what the goal is :-/ On the one hand I see why
> > > people might want function tracing / kprobes enabled, OTOH it's all
> > > mighty frigging scary. Any tracing/probing/whatever on an MCE has the
> > > potential to make a bad situation worse -- not unlike the same on #DF.
> 
> FWIW, I had this at the beginning of the #MC handler in a feeble attempt
> to poke at this:
> 
> +       hw_breakpoint_disable();
> +       static_key_disable(&__tracepoint_read_msr.key);
> +       tracing_off();

You can't do static_key_disable() from an IST