Re: [PATCH 6/7, RFC] x86_64: basic changes for supporting compatibility mode guest

["Jan Beulich" <jbeulich@novell.com>]

>>> Keir Fraser <Keir.Fraser@cl.cam.ac.uk> 23.08.06 11:40 >>>
>On 23/8/06 10:16 am, "Jan Beulich" <jbeulich@novell.com> wrote:
>
>> This changes the ABI in adding to vcpu_guest_context - does a change like
>> this require bumping the ABI version?
>
>We can't do this as the struct is part of the domU ABI (used for
>initialising secondary VCPUs). You'll have to add the extra CS values to
>64-bit arch_vcpu, I think.

Then libxc/xc_linux_build.c (after appropriate adjustment) wouldn't have
a way to communicate these for a new domain. If extending the structure
isn't possible at all, then we'll either have to make event_callback_eip and
failsafe_callback_eip unions (permitting a selector:offset pair) or make
syscall_callback_eip a union (permitting storing the selectors). I'd favor
the second option as that field is entirely useless as long as x86_32
doesn't support syscall (which doesn't make sense as it would make
things slower rather than speeding them up) - that way one doesn't have
to be careful to not access the other two full 64bit *_callback_eip
fields.

Jan