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From: Keir Fraser <keir@xensource.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Christian Limpach <Christian.Limpach@xensource.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
	Chris Wright <chrisw@sous-sol.org>, Andi Kleen <ak@muc.de>,
	<xen-devel@lists.xensource.com>,
	Ian Pratt <Ian.Pratt@xensource.com>,
	<virtualization@lists.osdl.org>,
	Steven Hand <steven.hand@cl.cam.ac.uk>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.
Date: Fri, 16 Feb 2007 10:47:11 +0000	[thread overview]
Message-ID: <C1FB3C2F.98E9%keir@xensource.com> (raw)
In-Reply-To: <20070216020947.03e1726e.akpm@linux-foundation.org>

On 16/2/07 10:09, "Andrew Morton" <akpm@linux-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


WARNING: multiple messages have this Message-ID (diff)
From: Keir Fraser <keir@xensource.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Christian Limpach <Christian.Limpach@xensource.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
	xen-devel@lists.xensource.com, virtualization@lists.osdl.org,
	Steven Hand <steven.hand@cl.cam.ac.uk>,
	linux-kernel@vger.kernel.org, Chris Wright <chrisw@sous-sol.org>,
	Andi Kleen <ak@muc.de>, Ian Pratt <Ian.Pratt@xensource.com>
Subject: Re: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.
Date: Fri, 16 Feb 2007 10:47:11 +0000	[thread overview]
Message-ID: <C1FB3C2F.98E9%keir@xensource.com> (raw)
In-Reply-To: <20070216020947.03e1726e.akpm@linux-foundation.org>

On 16/2/07 10:09, "Andrew Morton" <akpm@linux-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

  parent reply	other threads:[~2007-02-16 10:47 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-16 10:00 [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options Christian Limpach
2007-02-16 10:00 ` Christian Limpach
2007-02-16 10:09 ` Andrew Morton
2007-02-16 10:09   ` Andrew Morton
2007-02-16 10:47   ` Keir Fraser
2007-02-16 10:47   ` Keir Fraser [this message]
2007-02-16 10:47     ` Keir Fraser
2007-02-16 10:54     ` Andrew Morton
2007-02-16 10:54       ` Andrew Morton
2007-02-16 11:03       ` Keir Fraser
2007-02-16 11:03       ` Keir Fraser
2007-02-16 11:03         ` Keir Fraser
2007-02-16 17:46         ` [Xen-devel] " Jeremy Fitzhardinge
2007-02-16 17:46           ` Jeremy Fitzhardinge
2007-02-16 19:00           ` [Xen-devel] " Keir Fraser
2007-02-16 19:00           ` Keir Fraser
2007-02-16 19:00             ` Keir Fraser
2007-02-16 19:24             ` [Xen-devel] " Jeremy Fitzhardinge
2007-02-16 19:24               ` Jeremy Fitzhardinge
2007-02-16 21:51             ` [Xen-devel] " Zachary Amsden
2007-02-16 21:51               ` Zachary Amsden
2007-02-16 22:38               ` [Xen-devel] " Dan Hecht
2007-02-17 15:06                 ` Rik van Riel
2007-02-17 15:06                   ` Rik van Riel
2007-02-16 19:00           ` [Xen-devel] " Keir Fraser
2007-02-16 11:03       ` Keir Fraser
2007-02-16 10:47   ` Keir Fraser

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