Hi Jan,
On 21/04/2015 20:13, Jan Beulich wrote:
For this specific one - is there a reasonable use case? Other than
for host PFN, we have control over guest ones, and I'm not sure
managing a guest with GPFNs extending past 4 billion can be
expected to work if only this one hypercall got fixed. IOW I'm
expecting to NAK any such addition without proper rationale.
There is hardware coming out with 48 bits address support (i.e 36 bit pfn).
Even though the current layout of 64bit address space is using 40 bits
IPA, I wouldn't be surprise if we decide to extend it soon (I have in
mind PCI passthrough).
Without this new hypercall, you rule out the possibility to run the
toolstack (included memaccess or any software requiring the maximum PFN
used by a domain) in a 32bit domain or 32bit userspace on 64bit domain.
I don't have a good use case, but I don't see why we should omit a such
possibility. It would be better if we can fix now rather than waiting
until someone need it.
Regards,
--
Julien Grall
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