Features/ArchitectureSupport - x86_64 kernel 32 bit userspace

[Roberto Ragusa]

drago01 wrote:
> On Thu, Feb 26, 2009 at 11:54 AM, Roberto Ragusa <mail at robertoragusa.it> wrote:
>> Bill Nottingham wrote:
>>> - install x86_64 kernel on 32-bit OS where appropriate
>> This is really exciting, but I remember to have read somewhere of
>> some compatibility issues.
> 
> Should work (solaris had a similar setup and they supported it)

Agreed, I know it should work by default. Just wondering about
corner cases (the nvidia rumor, basically).

>> In particular, could someone report success/failure for the nvidia
>> binary module?
>> Is it true that the x86_64 kernel part depends on x86_64 GL/X11 part
>> which depends on x86_64 X11, which depends on x86_64 glibc... and so
>> the system is basically being entirely switched to x86_64?
> 
> No, but imho if you have a x86_64 capable machine you should be using x86_64

Well, yes, x86_64 is an option, but there could be reasons to live with
32bit userspace; for example if I have a proprietary 32bit app which would
require many i386 libs on x86_64, or just to have a development environment
where one can compile for i386 without worrying about compiler flags and
linking the right stuff, or just to avoid an installation from scratch
(upgrade i386->x86_64 is still unsupported, right?).

The nvidia problem was, IIRC, that something (arch dependent) is shared by
the kernel part and userspace part (sizes of passed data structures, maybe).
I was not able to find a reference to this discussion on the net,
so I'm asking here if anyone knows about that.
It would be bad design by nvidia, sure.

>> I think free stuff is compatible or fixable (kvm? fuse? openjdk? ...),
> 
> kvm should work fine, same for fuse.
> dunno why you ask about openjdk its just a regular userspace app.

You are right. Openjdk is JIT compiled, but there is no particular
kernel interaction.

>> but there is also widely used proprietary software
>> (ATI closed source driver? vmware? ...).
> 
> No idea, but they should be fine too. (besides nobody is stopping you
> from using a i586 if you really need/want that or just move to x86_64
> ;) )

Obviously yes. :-)

In fact, when I upgraded my laptop to 4GiB months ago, I wondered
about the alternatives:
a) switch to 32bit PAE
b) switch to x86_64 kernel
c) switch to x86_64 kernel and apps

I discarded c) for upgrade simplicity and avoided trying b) for the nvidia
issue we are talking about (so, I'm currently running a) ).

Best regards.
-- 
   Roberto Ragusa    mail at robertoragusa.it