Re: Replacement for page fault notifiers?

[Matt Mackall]

On Wed, 2008-01-09 at 16:42 -0800, Arjan van de Ven wrote:
> On Wed, 9 Jan 2008 20:22:54 +0000
> Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> 
> > On Thu, Jan 10, 2008 at 06:58:23AM +1100, Benjamin Herrenschmidt
> > wrote:
> > > It's a sane thing to do, Christoph, I don't think it's a
> > > unreasonable request to put the hooks back in.
> > 
> > As said a few times before there's simply no way we're going to put
> > exactly that crap back.  For one the patch removed a whole lot of
> > crud from the kprobes code that simply isn't going to come back just
> > because there are some pagefault notifiers.  Second the page fault
> > notifiers were horribly implemented and quite inefficient.  And third
> > we're not going to put something in just for out of tree code.
> > 
> 
> 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..);

That makes it way too easy for drivers of questionable legality to just
clear that bit. Also, we've got a shortage of page bits, etc.

-- 
Mathematics is the supreme nostalgia of our time.

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