linux-kernel - Re: [PATCH] x86_64: disable identity mappings statically

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Message-ID: <m14o8a34em.fsf@fess.ebiederm.org>
Date:	Fri, 11 Feb 2011 08:46:41 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86_64: disable identity mappings statically

Jiri Olsa <jolsa@...hat.com> writes:

> hi,
>
> while browsing the page table setup code, I noticed the x86_64 head
> code might not need the identity mappings at all.
> It seems it's ok to switch it off completely from the begining,
> unless I'm missing something.

Have you tested it?

I expect you will find that we need the identity mapping because
before we load this page table we are running with virt==phys
and we need the identity mapping retained  in the new page table
so we can get to the instruction after movq %rax, %cr0.

Eric
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