xen: implement an early timer for Xen PVH

When running as a PVH guest, there's no emulated i8254, so we need to
use the Xen PV timer as the early source for DELAY. This change allows
for different implementations of the early DELAY function and
implements a Xen variant for it.

Approved by: gibbs
Sponsored by: Citrix Systems R&D

dev/xen/timer/timer.c:
dev/xen/timer/timer.h:
 - Implement Xen early delay functions using the PV timer and declare
   them.

x86/include/init.h:
 - Add hooks for early clock source initialization and early delay
   functions.

i386/i386/machdep.c:
pc98/pc98/machdep.c:
amd64/amd64/machdep.c:
 - Set early delay hooks to use the i8254 on bare metal.
 - Use clock_init (that will in turn make use of init_ops) to
   initialize the early clock source.

amd64/include/clock.h:
i386/include/clock.h:
 - Declare i8254_delay and clock_init.

i386/xen/clock.c:
 - Rename DELAY to i8254_delay.

x86/isa/clock.c:
 - Introduce clock_init that will take care of initializing the early
   clock by making use of the init_ops hooks.
 - Move non ISA related delay functions to the newly introduced delay
   file.

x86/x86/delay.c:
 - Add moved delay related functions.
 - Implement generic DELAY function that will use the init_ops hooks.

x86/xen/pv.c:
 - Set PVH hooks for the early delay related functions in init_ops.

conf/files.amd64:
conf/files.i386:
conf/files.pc98:
 - Add delay.c to the kernel build.

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/x86/include/init.h b/sys/x86/include/init.h
index 7e032df214fe..c72889f0209b 100644
--- a/sys/x86/include/init.h
+++ b/sys/x86/include/init.h
@@ -36,6 +36,8 @@
  */
 struct init_ops {
 	caddr_t	(*parse_preload_data)(u_int64_t);
+	void	(*early_clock_source_init)(void);
+	void	(*early_delay)(int);
 };
 
 extern struct init_ops init_ops;