Hi, a PAE domU will not work on a non-PAE dom0 - is that correct for a 32bit system? Or does it depend on the used version of Xen? Best regards, Mark Weinem -- Mark Weinem Jabber: weinem@jabber.cz _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson
2007-Dec-04 03:57 UTC
Re: [Xen-users] Does a PAE domU work with non-PAE dom0?
> a PAE domU will not work on a non-PAE dom0 - is that correct for a 32bit > system? Or does it depend on the used version of Xen?On 32-bit Xen all the PV guests have to match Xen. So if Xen is PAE then dom0 and all domUs must be PAE. If Xen is non-PAE then dom0 and all domUs must be non-PAE. You can''t mix PAE and non-PAE. On 64-bit Xen, PV guests (including dom0) can be 64-bit or 32-bit PAE. 32-bit non-PAE PV guests won''t run. HVM guests can have any memory mode "equal or less than" the Xen memory mode. e.g. 32-bit non-PAE only on 32-bit non-PAE Xen. 32-bit PAE or non-PAE on PAE Xen. 32-bit non-PAE, 32-bit PAE, 64-bit on 64-bit Xen. Hope that helps, Cheers, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
James Harper
2007-Dec-04 04:38 UTC
RE: [Xen-users] Does a PAE domU work with non-PAE dom0?
> > On 64-bit Xen, PV guests (including dom0) can be 64-bit or 32-bit PAE. > 32-bit > non-PAE PV guests won''t run. > > HVM guests can have any memory mode "equal or less than" the Xenmemory> mode. > e.g. 32-bit non-PAE only on 32-bit non-PAE Xen. 32-bit PAE or non-PAEon> PAE > Xen. 32-bit non-PAE, 32-bit PAE, 64-bit on 64-bit Xen.Just out of interest, with a 64-bit hypervisor, which of the HVM options (32, 32p, 64) will give the lowest overhead? Or are they going to be more the same than they are different? Thanks James _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson
2007-Dec-04 04:52 UTC
Re: [Xen-users] Does a PAE domU work with non-PAE dom0?
> Just out of interest, with a 64-bit hypervisor, which of the HVM options > (32, 32p, 64) will give the lowest overhead? Or are they going to be > more the same than they are different?Hmmm. I suspect they''re more the same than different... It *might* be that one or the other reduces the overhead of maintaining shadow pagetables. But I wouldn''t be surprised if they came out fairly similar in terms of overhead. Of course, if you use a 64-bit guest then the guest applications get the advantage or a larger virtual memory space and of extra registers, so they may benefit in performance because of that. Amusingly for PV guests, I strongly suspect the overhead is lower when running 32-bit PAE guests on 64-bit Xen than when running native 64-bit guests. That may well extend to dom0 too. Also, glibc''s negative segment offset tricks would work for 32-bit guests under 64-bit Xen at full performance... Crazy stuff ;-) Cheers, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users