linux-kernel - Re: Dealing with the NMI mess

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Message-ID: <20150724160806.GF3612@1wt.eu>
Date:	Fri, 24 Jul 2015 18:08:06 +0200
From:	Willy Tarreau <w@....eu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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 12:02:49PM -0400, Steven Rostedt wrote:
> On Fri, 24 Jul 2015 08:48:57 -0700
> Andy Lutomirski <luto@...capital.net> wrote:
> 
> > So by the time we detect that we've hit a watchpoint, the instruction
> > that tripped it is done and we don't need RF.  Furthermore, after
> > reading 17.3.1.1: I *think* that regs->flags withh have RF *clear* if
> > we hit a watchpoint.  So this might be as simple as:
> > 
> > if ((dr6 && (0xf * DR_TRAP0) && (regs->flags & (X86_EFLAGS_RF |
> 
> Um, isn't 0xf * DR_TRAP0 same as a constant "true"?

For me it's a typo, it should have been :

 if ((dr6 & (0xf * DR_TRAP0) && (regs->flags & (X86_EFLAGS_RF |

(the purpose was to read all 4 lower bits at once).

Willy

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