linux-kernel - Re: [RFC] #MC mess

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Message-ID: <20200218205224.GT14449@zn.tnic>
Date:   Tue, 18 Feb 2020 21:52:24 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>, x86-ml <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] #MC mess

On Tue, Feb 18, 2020 at 03:08:50PM -0500, Steven Rostedt wrote:
> You could have the msr_tracepoint_active() check this per cpu variable?
> 
> msr reading and writing is rather slow, and I'm sure reading a per_cpu
> variable is going to be in the noise of it.

Yeah, I was worrying about using the tracing MSR variants in NMI context
but Peter says tracing should do in_nmi() if it isn't doing so.

Same with #MC: we hold a subsequent #MC from getting raised with MCIP -
thanks Tony - but we can have other exceptions raised while in the #MC
handler. That too should be taken care of with the in_nmi() thing.

Thx.

-- 
Regards/Gruss,
    Boris.

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