linux-kernel - Re: Replacement for page fault notifiers?

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Message-ID: <20080109165515.4a6256a8@laptopd505.fenrus.org>
Date:	Wed, 9 Jan 2008 16:55:15 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Pavel Roskin <proski@....org>, Dave Airlie <airlied@...il.com>,
	Pekka Paalanen <pq@....fi>, linux-kernel@...r.kernel.org,
	jbeulich@...ell.com
Subject: Re: Replacement for page fault notifiers?

On Thu, 10 Jan 2008 01:47:16 +0100
Andi Kleen <andi@...stfloor.org> wrote:

> Arjan van de Ven <arjan@...radead.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
> 

so you also call the function for all traps on pages without struct page;
that should be extremely rare anyway, and the mmio_trace code can then 
look the page up.

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