Re: [Xen-users] Xen and OS X.

["Austin S. Hemmelgarn" <ahferroin7@xxxxxxxxx>]

On 2016-07-25 10:40, Simon Hobson wrote:
> George Dunlap <george.dunlap@xxxxxxxxxx> wrote:
>
> > More specifically, one of the things that makes Apple's life a lot
> > easier than Microsoft's is that they only need OS X to run on a small
> > handful of hardware platforms -- platforms which Apple controls.
> > Unlike Windows, which needs to run on any PC, or Linux, which runs on
> > just about everything on the planet, OS X assumes that it's running on
> > an Apple hardware platform and will simply fail if you try to boot it
> > on a platform that doesn't look like an Apple system.
> You need to differentiate between two distinct aspects. AIUI :
>
> 1) One is hardware compatibility. Apple hardware isn't that special these days - and on 
> the various forums etc you'll find information on what hardware is "supported" 
> (as in, has drivers etc). In that respect, Xen isn't so different either - if you have a 
> supported CPU and emulate supported devices (eg NICs) then that's half the battle.
As you say, this is the easy bit, QEMU can emulate all the hardware 
Darwin needs to run, and almost all that a full OS X system needs, so 
it's doable with a HVM domain on Xen (I've actually run Darwin (without 
OS X on top) in QEMU before, and while I've never tried it on Xen, I 
suspect it's not much more difficult).
> 2) The biggie is that there is code which explicitly checks for Apple hardware and deliberately 
> stops the boot if it's "not genuine". So a big chunk of the Hackintosh task is in working 
> around this code, and dependencies on it. It's not so much booting a "non-Apple but OS X 
> like" kernel, but booting the real Apple OS X kernel, but working around the bits that are 
> designed to break the system.
This is what usually gets people.  I haven't looked recently at what all 
is involved, but I'm pretty certain there's multiple places that the OS 
directly executes bits of firmware to verify things, and that handshake 
is the really tough part.  There's other stuff too though, if certain 
types of hardware present in ways OS X doesn't expect, it may refuse to 
boot also (although this is partly to protect against running on 
hardware that's actually broken).
> > In either case, you'd be in questionable legal waters with regard to
> > the license for Apple's software (or at least this used to be the
> > case), so take care.
> Indeed. Though given how many forums/sites are still up after quite a long life, one has to suspect that 
> Apple might be taking a slightly "pragmatic" approach to things. Yes, if you try and make money 
> from it, they very publicly come down like the proverbial ton of bricks - but it does appear that they at 
> least turn a bit of a blind eye to "personal use". That's just conjecture based on observation - 
> perhaps they'd rather have those personal user on board and perhaps they'll get converted into 
> "real" paying users over time ?
Which is an odd stance IMHO, because most people I know who use 
Hackintosh stuff do so because they don't want to spend the money on 
hardware that isn't end-user repairable and depreciates faster than 
other systems.
> Then there's the grey areas. Parallels won't run OS X 10.6 as a VM - but there is a 
> workaround which makes the system "look like" it's a server version (and then 
> Parallels will run it). The difference is that the EULA for the server version permits 
> virtualisation (on Apple hardware), the desktop version permits only running on Apple 
> hardware.
The big question is where the verification is.  I'm pretty certain that 
there's mutual verification between the hypervisor and the OS in this 
case, it's just that the OS is more permissive (I'd be more than willing 
to bet that this is due to Apple using VM's internally for testing of 
the desktop version).
> I've had people who really you would expect to know better argue that when you virtualise 
> a system (in this case, with Parallels and hosted on Apple hardware), it's no longer 
> running on the Apple hardware. So it's held in the same RAM, it executes on the same CPU, 
> but it's no longer running on the Apple hardware ... that's an "interesting" 
> interpretation.
The argument here as I understand it is that the firmware is different, 
thus it's not an Apple platform, and they technically are correct in 
that respect.  It's running on the same _hardware_, but for an OS, the 
firmware is an integral part of the hardware these days, and a firmware 
update does mean you're not running on the same system (especially if 
you're using SecureBoot).
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