To: Andrea Arcangeli <andrea@qumranet.com>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
       Nick Piggin <npiggin@suse.de>
Subject: Re: [PATCH] reserve RAM below PHYSICAL_START
From: Andi Kleen <andi@firstfloor.org>
References: <20080227003325.GS28483@v2.random>
Date: Mon, 03 Mar 2008 13:17:46 +0100
In-Reply-To: <20080227003325.GS28483@v2.random> (Andrea Arcangeli's message of "Wed\, 27 Feb 2008 01\:33\:25 +0100")
Message-ID: <p73ve446lxx.fsf@bingen.suse.de>
User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1084
Lines: 29

Andrea Arcangeli <andrea@qumranet.com> writes:

> Hello,
>
> this patch allows to prevent linux from using the ram below
> PHYSICAL_START.
>
> The "reserved RAM" can be mapped by virtualization software with to
> create a 1:1 mapping between guest physical (bus) address and host
> physical (bus) address.

Wouldn't it be easier if your virtualization software just marked
that area reserved or unmapped in its e820 map? 

Of if you don't want that you can get the same result with mem=... 
arguments (e.g commonly used by crash dumping) 

Even if that was all not possible for some reason having CONFIG for this would
seem unfortunate for me -- i don't think users really want specially
compiled kernels for specific hypervisors. With paravirt Linux
is trying to get away from that. Some runtime setup method
would be much better.

-Andi
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/