RE: [Xen-devel] xen_phys_start for 32b

["Cihula, Joseph" <joseph.cihula@xxxxxxxxx>]

> From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
> Sent: Tuesday, January 06, 2009 2:12 PM
>
> On 06/01/2009 18:29, "Cihula, Joseph" <joseph.cihula@xxxxxxxxx> wrote:
>
> > I don't understand the reason for this last assignment on 32b systems, since
> > xen isn't really using this low memory for its heap.
>
> It's not used for domheap either. In fact it's not really used at all. Hence
> encompassing it within xenheap_phys_start to xenheap_phys_end works okay.
>

But shouldn't [xenheap_phys_start, xenheap_phys_end] represent all of the 
memory that the hypervisor "owns" and which must be protected from even 
privileged domain writes (modulo the real mode/trampoline code, which has its 
own variables that represent its range)?  While it may be "OK" on 32b systems, 
it is not "logically correct" and does not match 64b systems (where this low 
memory is not so protected).  Would it break anything to set xenheap_phys_start 
to __pa(&_start) for 32b builds?

Joe

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