[Xen-users] Re: [Xen-devel] Re: How to build a 64 bit xen

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 16:20 +0100 on 18 May (1274199615), Ian Campbell wrote:
> On Tue, 2010-05-18 at 16:13 +0100, George Dunlap wrote:
> > I've cross-compiled 64-bit xen exclusively since I've worked for
> > XenSource basically.  Here's what I get:
> > 
> > $ file xen/xen
> > xen/xen: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
> > statically linked, stripped
> > $ file xen/xen-syms
> > xen/xen-syms: ELF 64-bit LSB executable, x86-64, version 1 (SYSV),
> > statically linked, not stripped
> > 
> > So I think 'file' is just making a mistake.
> 
> The 64 bit hypervisor really is encapsulated in a 32 bit container, see
> the mkelf32 related rules in xen/arch/x86/Makefile.
> 
> I'm not sure why. Something to do with 32 bit bootloaders maybe?

Yep.  The Multiboot standard specifies that the kernel should be started
in 32-bit protected mode with flat 4GB segments.  Xen bootstraps itself
from there up into 64-bit mode.

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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