[REGRESSION] 2.6.32.36 - Linux Xen DomU doesn't boot anymore

["guilherme m. schroeder" <guilherme.m.schroeder@gmail.com>]

Hi,

Linux Kernel 2.6.32.36 introduced a regression that prevents Linux Xen
DomU from booting.
Linux DomU starts and after a while it shutdown without log messages.

I bisected a vanilla kernel from 2.6.32.36 (bad) to 2.6.32.32 (good)
and got this commit:

vm:~/linux-2.6.32.y# git bisect bad
856460aa905dcc6d11a05a832d487a7b0ce69402 is the first bad commit
commit 856460aa905dcc6d11a05a832d487a7b0ce69402
Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Date:   Fri Feb 18 11:32:40 2011 +0000

    xen: set max_pfn_mapped to the last pfn mapped

    commit 14988a4d350ce3b41ecad4f63c4f44c56f5ae34d upstream.

    Do not set max_pfn_mapped to the end of the initial memory mappings,
    that also contain pages that don't belong in pfn space (like the mfn
    list).

    Set max_pfn_mapped to the last real pfn mapped in the initial memory
    mappings that is the pfn backing _end.

    Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
    Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    LKML-Reference: <alpine.DEB.2.00.1103171739050.3382@kaball-desktop>
    Signed-off-by: H. Peter Anvin <hpa@zytor.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

:040000 040000 a679f50b64c290b9a51e3dba8d3d648bca50fdf0
e7b018c4e0015aae44ed6f9f6323d8b13d032b86 M	arch

I have tested against XCP 1.0, Citrix XenServer 5.6 and 5.6 FP1.
Without this patch, Linux DomU boots and runs fine.
If more info is needed, please let me know.