linux-kernel - Re: [PATCH v9 2/3] trace,x86: add x86 irq vector tracepoints

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Date:	Mon, 18 Feb 2013 23:24:14 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Seiji Aguchi <seiji.aguchi@....com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Thomas Gleixner (tglx@...utronix.de)" <tglx@...utronix.de>,
	"'mingo@...e.hu' (mingo@...e.hu)" <mingo@...e.hu>,
	"Borislav Petkov (bp@...en8.de)" <bp@...en8.de>,
	Satoru Moriya <satoru.moriya@....com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>
Subject: Re: [PATCH v9 2/3] trace,x86: add x86 irq vector tracepoints

On Mon, 2013-02-18 at 15:49 -0800, H. Peter Anvin wrote:

> What about the following:
> 
> > The base address of the IDT doesn't generally change... the one
> > exception is when we do the funny NMI workaround.
> >
> > For that reason, I would be happier if we just restored the standard
> > value instead of saving/restoring stuff.

Basically what you are saying, is to have his code do what the NMI code
originally did, but can't now, due to there being another IDT table
(from Seiji's changes).

static void switch_to_trace_idt(void *arg)
{
     load_idt(&trace_idt_descr);
}

static void restore_original_idt(void *arg)
{
     load_idt(this_cpu_ptr(&idt_descr));
}

-- Steve


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