From: Andrew Morton <akpm@osdl.org>
Subject: Re: [patch 7/8] Add a bootparameter to reserve high linear address
 space.
Date: Wed, 2 Aug 2006 23:19:12 -0700
Message-ID: <20060802231912.ed77f930.akpm@osdl.org>
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To: Jeremy Fitzhardinge <jeremy@xensource.com>
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On Wed, 02 Aug 2006 17:25:17 -0700
Jeremy Fitzhardinge <jeremy@xensource.com> wrote:

> +		/*
> +		 * reservetop=size reserves a hole at the top of the kernel
> +		 * address space which a hypervisor can load into later.
> +		 * Needed for dynamically loaded hypervisors, so relocating
> +		 * the fixmap can be done before paging initialization.
> +		 * This hole must be a multiple of 4M.
> +		 */
> +		else if (!memcmp(from, "reservetop=", 11)) {
> +			unsigned long reserve = memparse(from+11, &from);
> +			reserve &= ~0x3fffff;
> +			reserve_top_address(reserve);
> +		}

I assume that this argument will normally be passed in via the hypervisor
rather than by human-entered information?

In which case, perhaps a panic would be a more appropriate response to a
non-multiple-of-4M.

Either way, rounding the number down rather than up seems wrong...