linux-kernel - Re: Dealing with the NMI mess

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Message-ID: <20150724145901.GB3612@1wt.eu>
Date:	Fri, 24 Jul 2015 16:59:01 +0200
From:	Willy Tarreau <w@....eu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: Dealing with the NMI mess

On Fri, Jul 24, 2015 at 10:31:27AM -0400, Steven Rostedt wrote:
> On Fri, 24 Jul 2015 15:21:28 +0200
> Willy Tarreau <w@....eu> wrote:
> 
> > My understanding is that by using RET we can't set the RF flag and #DB
> 
> But the RF flag is only set for instruction (executing) breakpoints. It
> is not set for data (RW) ones.

True but these also are the most complicated to deal with. The data
accesses can always be emulated (not what I'm suggesting here) while
instructions are much harder to emulate.

Willy

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