Re: [Xen-users] Mixing architectures--64bit master, 32bit clients?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Sorry for the real newbie questions here, but how can I look at my
> existing
> xen 3.0.2 installation (installed by someone else before I took over)
> and tell which kind of client I've got now, HVM or PAE or non-PAE?
> And is there a basic howto that will define some of these acronyms?

HVM is full virtualisation.  PAE is the mode of x86-32 which supports large 
memory systems, non-PAE is limited at 4Gig of physical address space (which 
in practice means a bit less than 4Gig ram maximum).

PAE and non-PAE are the standard ways of doing 32-bit guests (they support the 
same userspace, it's just the kernel that's different).

If your guests are Xen-aware then they're not HVM.  If they're running 
standard native installs and are fully virtualised, that's HVM.

If you run xm info it'll tell you what kind of guests your hardware supports.

> Also, when upgrading from Xen 3.0.2 to xen 3.0.4 (kernel
> 2.6.16-xen3_86.1_rhel4.1 to 2.16.16.33-)
> is there any order that should be followed, i.e. should you
> do the master first or the clients first, or does it matter?

Doesn't necessarily matter...  if the guests are compiled with support for 
compatibility with older Xen either way should probably work.  If you upgrade 
the master stuff (Xen, dom0 stuff, etc) first then the unprivileged clients 
will definitely continue to work.

Regarding dom0 stuff: The versions of Xen and the toolset must match.  There's 
no longer the requirement in 3.0.4 that the dom0 kernel matches too so you 
may not need to upgrade this immediately... (I'm not sure if that'll work, 
but you could try it and upgrade the kernel later if necessary).

As always, keep a known-good native kernel handy in case you need to boot and 
fix anything!

Cheers,
Mark

> Thanks
>
> Steve timm
>
> > For paravirtualised guests, 3.0.4 requires them to have the same paging
> > model (i.e. 64-bit / 32-bit, and for the latter PAE or non PAE).
> >
> > xen-unstable has (I believe) support for mixing paravirtualised 32-bit
> > PAE guests and 64-bit paravirtualised guests on a 64-bit Xen.  Dom0 can
> > also be 32-bit in this scenario.
> >
> > 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!

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