linux-kernel - Re: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.

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Date:	Fri, 16 Feb 2007 10:47:11 +0000
From:	Keir Fraser <keir@...source.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Christian Limpach <Christian.Limpach@...source.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Chris Wright <chrisw@...s-sol.org>, Andi Kleen <ak@....de>,
	<xen-devel@...ts.xensource.com>,
	Ian Pratt <Ian.Pratt@...source.com>,
	<virtualization@...ts.osdl.org>,
	Steven Hand <steven.hand@...cam.ac.uk>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [patch 14/21] Xen-paravirt: Add XEN config options and
 disableunsupported config options.

On 16/2/07 10:09, "Andrew Morton" <akpm@...ux-foundation.org> wrote:

> Are the places where the domU code references machine addresses splattered
> all over the code?  If not, they can just be wrapped with
> preempt_disable/preempt_enable?

The main places where machine addresses are 'visible' are any code that
holds a pte_t,pmd_t,pud_t,pgd_t. We hide the machine-to-pseudophysical and
pseudophysical-to-machine translations inside e.g., pte_val() and __pte()
(i.e., constructors and extractors for page table entries). Obviously the
users of these macros are open coded all over the place, quite apart from
the performance cost of sprinkling preempt_{enable,disable} so liberally.

 -- Keir

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