>>> Julien Grall <julien.gr...@citrix.com> 04/25/15 10:37 PM >>> >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.
For a 32-bit domain, I suppose there are more limitations (unsigned long being used for MFNs/PFNs), so I don't see how this one addition would help. For 32-bit userspace on 64-bit domains the hypercall again isn't the limiting factor, but the kernel's hypercall interface is. (And again I doubt widening the MFN/PFN/GFN representation just here would really make 32-bit userspace work on such large hosts.) Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
