Bug#421804: Acknowledgement (linux-image-2.6.18-4-xen-686: Can crash at boot w/ >4GB memory)

[Ian Campbell <Ian.Campbell@XenSource.com>]

It turns out that there was a hypervisor side workaround for this issue
for a while now but it was broken in xen-unstable.hg between
13392:0fd65225e4c6 (17 Jan 2007) and 15433:a5360bf18668 (28 June 2007).
The workaround is in xen/arch/x86/mm.c with the comment (line 3297 in
current xen-unstable):
        /*
         * If this is an upper-half write to a PAE PTE then we assume
        that
         * the guest has simply got the two writes the wrong way round.
        We
         * zap the PRESENT bit on the assumption that the bottom half
        will
         * be written immediately after we return to the guest.
         */

I suspect the hypervisor in Etch has the workaround but not the
breakage. If so this bug can be closed.