The Xen hypercall interface is allowed to trash any or all of the
argument registers, so we need to be careful that the kernel state
isn't damaged.  On 32-bit kernels, the hypercall parameter registers
same as a regparm function call, so we've got away without explicit
clobbering so far.  The 64-bit ABI defines lots of caller-save
registers, so save them all for safety.  We can trim this set later by
re-distributing the responsibility for saving all these registers.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>