Re: [Xen-devel] 32bit xen and "claim"

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.11.12 at 21:40, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> wrote:
>>  From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: Tuesday, November 06, 2012 2:44 AM
>> To: Dan Magenheimer
>> Cc: xen-devel@xxxxxxxxxxxxx; keir@xxxxxxx 
>> Subject: RE: 32bit xen and "claim"
>> 
>> >>> On 05.11.12 at 20:16, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> wrote:
>> > Does it make sense to have a runtime option that unsets the
>> > physical limit but disallows legacy PV guests?  If this
>> > defaults to false for machines with RAM<=5TB but to true
>> > for machines with RAM>5TB, then the feature is "done"
>> > (AND we have put a stake in the ground to begin the
>> > slow obsolescence of PV functionality).
>> 
>> That would be interesting: Mukesh's PVH code wasn't even
>> posted yet, i.e. you're proposing to render systems with more
>> than 5Tb unbootable (for the lack of a - necessarily PV - Dom0
>> kernel runnable in that environment).
> 
> Good point.  BUT... couldn't a PV dom0 started with dom0_mem=X
> (where X is smaller than 5GB) still work?

No - Xen would still need to be able to access all memory when in
the context of such a Dom0 (even address restricting that Dom0
just like we do for 32-bit PV guests wouldn't help, as e.g. granted
pages from DomU-s may need accessing in Xen in the context of
Dom0).

Jan


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