Re: [Xen-users] Xen on a MacBook Pro? The ultimate developer setup?

[Eric Shelton <eshelton@xxxxxxxxx>]

Jason,

I have a MacBook Air 2012 running Xen (specifically, with Qubes OS,
discussed below), and it is a very good experience.  However, I have
become very frustrated that with only 4 GB of RAM, and no RAM upgrade
path other than purchasing a new system, it is difficult to get more
than one RAM-hungry consumer OS (esp OS X, which does not support
ballooning AFAIK) running at the same time.  This would not be a
problem with your system, I think.

Although you may be unfamiliar with Xen (and the learning curve
somewhat steep), I would not necessarily abandon the idea of its use.
Instead, consider having a more packaged experience.  Although don't
worry - will still be plenty of obscure issues and arcane
configuration file settings (pretty much the Linux experience, I
suppose).

Specifically, check out Qubes OS (http://qubes-os.org/).  Not only can
you pursue the benefits you originally brought up, but you will learn
and come across a lot of interesting ideas with Qubes, such as
resource and service disaggregation for improved security.  There is a
white paper that, although it does not fully reflect the current Qubes
architecture, is a reasonable primer.  There are some profound
differences in how a properly-used Qubes environment works versus the
more ordinary OS (mainly a result of OS isolation).

As to the use of Qubes specifically on Mac hardware, check out:
https://groups.google.com/forum/?fromgroups=#!topic/qubes-devel/uLDYGdKk_Dk
(what it took to get my MacBook Air running, including a workaround of
a buggy ACPI table entry to get the IOMMU working)
https://groups.google.com/forum/?fromgroups=#!topic/qubes-devel/hag-MQDH_Vs
(a report for a MacBook Pro 6,2, which cannot provide an IOMMU)

I would guess (but have absolutely no experience with this) that
something like Citrix XenClient might also give you a more polished
and packaged experience to start with.  Odds are that some Google
searching woud lead you to at least one person who has detailed their
use of a MacBook.

I have not yet managed to virtualize OS X on my MacBook under Xen.  It
is somewhat disappointing that "it just works" in VirtualBox.  My
experience with OpenSolaris/Illumos has sadly been pretty much the
same.  On top of that, these failures have not been particularly
"debuggable" (especially on a machine lacking in ports).  Instead, if
you are lucky, you eventually arrive at a working combination of
configuration settings.  For example, recent things I came across were
(1) passing "cpu=host" to qemu-upstream breaking FreeBSD (of course,
it works just fine for the older version of qemu...), and (2) labeling
an exported drive with "xvda" versus "hda" making a difference.
Ultimately, it seems that Linux and Windows are the only OSes you can
count on working under Xen, as they are what everyone is trying to
use.

That said, there are reports of OS X running under Xen.
http://www.contrib.andrew.cmu.edu/~somlo/OSXKVM/ probably offers the
best leads, particularly on the SMC issue.

Macs are not outright hostile to non-OS X installs, just very
difficult.  Probably the only reason they manage to boot other OSes
was the demand for Bootcamp-type dual booting of Windows.

With a MacBook, note that it is hit-or-miss whether the hardware will
provide IOMMU functionality, as it appears OS X does not make use of
it.  With Intel, BOTH the CPU and the NB/SB chipset have to support
Vt-D.  It can be surprisingly tricky to determine exactly which models
you have, and what support they offer in combination.  Then, on top of
that, many BIOS vendors have managed to screw up otherwise good
hardware by not correctly configuring the hardware, or providing
incorrect ACPI tables.

The desktop computer world, if you are not buying server-grade
hardware, is plagued with similar problems.  For example, it is just
about impossible to find a 970 chipset motherboard with a functioning
IOMMU (my favorite failed MB would clobber the USB port, and
consequently the keyboard, by the BIOS setting for IOMMU enable).
Even now, the board I settled with his a partially defective BIOS that
maybe the vendor will someday get around to fixing.

Note, however, that although IOMMU is "nice", but is often missing, it
is not necessary for virtualization. You can still run something like
Xen on most modern machines.

Best of luck,
Eric

> Fajar,
>
> > >> 4. Can one extend Xen so that I could scp into the hypervisor and
> > >> backup the vm's if I needed to?
> > >
> > > Not sure why you think you'd need to "extend Xen".  Can't imagine that
> > > you'll ever "scp into the hypervisor"; you could scp into the dom0, if
> > > you wanted to set that up.  More likely, you'd run your domUs on LVs and
> > > scp *from* the dom0, from mounted snapshots.  Or copy to a USB drive.
> >
> >
> > @Mike: I think the main issue is that Jason thinks Xen is a drop-in
> > replacement for vmware workstation. It's not.
> >
> > @Jason: You can try the live cd, but IMHO it's not worthed. Looking at
> > your questions, it seems you'd be better off with virtualbox or
> > vmware. Seriously.
>
> Yes, that is seriously my confusion. Xen being a drop-in replacement for
> VmWare. I supposed I have misinformation.
>
> And here I was hoping for a dream! I mean wouldn't it be a fantastic setup?
> The ability to boot ones machine, have other OS's running along side each 
> other,
> interact with them on a modern laptop that has the space and RAM to
> accomodate it. switch back and forth between your environments with ease.
>
> I wish I could put my development skills to use on something interesting and 
> awesome.
>
> Jason

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