xen: generate hypercall interface related code

Instead of repeating similar data multiple times use a single source
file and a generator script for producing prototypes and call sequences
of the hypercalls.

As the script already knows the number of parameters used add generating
a macro for populating an array with the number of parameters per
hypercall.

The priorities for the specific hypercalls are based on two benchamrks
performed in guests (PV and PVH):

- make -j 4 of the Xen hypervisor (resulting in cpu load with lots of
  processes created)
- scp of a large file to the guest (network load)

With a small additional debug patch applied the number of the
different hypercalls in the guest and in dom0 (for looking at backend
activity related hypercalls) were counted while the benchmark in domU
was running:

PV-hypercall    PV-guest build   PV-guest scp    dom0 build     dom0 scp
mmu_update           186175729           2865         20936        33725
stack_switch           1273311          62381        108589       270764
multicall              2182803             50           302          524
update_va_mapping       571868             10            60           80
xen_version              73061            850           859         5432
grant_table_op               0              0         35557       139110
iret                  75673006         484132        268157       757958
vcpu_op                 453037          71199        138224       334988
set_segment_base       1650249          62387        108645       270823
mmuext_op             11225681            188          7239         3426
sched_op                280153         134645         70729       137943
event_channel_op        192327          66204         71409       214191
physdev_op                   0              0          7721         4315
(the dom0 values are for the guest running the build or scp test, so
dom0 acting as backend)

HVM-hypercall   PVH-guest build    PVH-guest scp
vcpu_op                  277684             2324
event_channel_op         350233            57383
(the related dom0 counter values are in the same range as with the test
running in the PV guest)

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>

.gitignore

@@ -327,6 +327,7 @@ xen/include/public/public
 xen/include/xen/*.new
 xen/include/xen/acm_policy.h
 xen/include/xen/compile.h
+xen/include/xen/hypercall-defs.h
 xen/include/xen/lib/x86/cpuid-autogen.h
 xen/source
 xen/test/livepatch/config.h