linux-kernel - Re: [patch] x86: optimize __pa() to be linear again on 64-bit x86

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Message-ID: <87zlgb3juu.fsf@basil.nowhere.org>
Date:	Tue, 24 Feb 2009 17:00:57 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>, Tejun Heo <tj@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	rusty@...tcorp.com.au, tglx@...utronix.de, x86@...nel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com, jeremy@...p.org,
	cpw@....com
Subject: Re: [patch] x86: optimize __pa() to be linear again on 64-bit x86

Ingo Molnar <mingo@...e.hu> writes:
>
> Yeah, we can do this complete conversion.
>
> I'll clean it up some more. I think the best representation of 
> this will be via a virt_to_sym() and sym_to_virt() space. That 
> makes it really clear when we are moving from the symbol space 
> to the linear space and back.
>
> That way we wont need the _slow() methods at all - we'll always 
> know whether an address is pure linear or in the symbol space.
>
> In other words, it will be even faster and even nicer ;-)

That is what the original code did (virt_to_sym was just
done through __pa_symbol), but it was sometimes tricky 
to get right andLinus wanted an unified __pa/__va
and put it out of line.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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