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To: Arjan van de Ven <arjan@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Pavel Roskin <proski@gnu.org>, Dave Airlie <airlied@gmail.com>,
       Pekka Paalanen <pq@iki.fi>, linux-kernel@vger.kernel.org,
       jbeulich@novell.com
Subject: Re: Replacement for page fault notifiers?
From: Andi Kleen <andi@firstfloor.org>
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Date: Thu, 10 Jan 2008 01:47:16 +0100
In-Reply-To: <20080109164241.7daa5770@laptopd505.fenrus.org> (Arjan van de Ven's message of "Wed\, 9 Jan 2008 16\:42\:41 -0800")
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Arjan van de Ven <arjan@infradead.org> writes:
>
> I'm btw all in favor of making mmio tracing full fledged kernel infrastructure.
> This doesn't mean "notifier" imo; this means a real flag in the struct page,
> and then the page fault code can do
>
> if (page->flags & FLAG_MMIO_TRACED)
> 	mmio_trace(page, regs, whatever..);
>
> (probably surrounded by a CONFIG_ ifdef)
> THis is a TON lighter than a notifier chain, and actually what you want,
> you don't really want a notifier, you want a call back when a special kind of
> page is touched.

That would assume that your mmio area has a struct page. In most PCs 
the ones in the PCI hole don't

-Andi