linux-kernel - Re: [PATCH] x86: use pgd accessors when cloning a pgd range.

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Message-ID: <20101028112052.GA21757@a1.tnic>
Date:	Thu, 28 Oct 2010 13:20:52 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH] x86: use pgd accessors when cloning a pgd range.

On Thu, Oct 28, 2010 at 10:23:17AM +0100, Ian Campbell wrote:
> Now tested and it works. Patch below.

I'm assuming you tested bare metal too?

> I'm also going to look into switching Xen to startup on
> initial_page_table, since I think the consistency with native would be
> useful from a principle of least surprise PoV. However the following
> is a useful stopgap if nothing else.

Sounds good. Then we can drop this temporary workaround.

> BTW, are there plans to unify 32 and 64 bit WRT the use of
> swapper_pg_dir vs initial_page_table?

To be honest, I thought about it but 64bit does the bootstrapping
differently. I'll look into it one fine day when there's time. (like
there ever is :))

> From: Ian Campbell <ian.campbell@...rix.com>
> Date: Thu, 28 Oct 2010 10:16:52 +0100
> Subject: [PATCH] x86/32: skip early initialisation of swapper_pg_dir if it is already current
> 
> In particular in the Xen PV case the Xen early startup code has
> already initialised swapper_pg_dir and switched to it. In this case
> initial_page_table is uninitialised since Xen has no use for it so
> copying it over swapper_pg_dir is not correct.
> 
> Signed-off-by: Ian Campbell <ian.campbell@...rix.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: H. Peter Anvin <hpa@...ux.intel.com>
> Cc: Jeremy Fitzhardinge <jeremy@...p.org>

Acked-by: Borislav Petkov <bp@...en8.de>

-- 
Regards/Gruss,
Boris.
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