arm64: add exception_hwinit()

exception_hwinit() provides a path for just setting the hardware
state. This allows for other CPUs but the boot CPU for setting up
the appropriate vector table.

BUG=chrome-os-partner:31545
BRANCH=None
TEST=Built and booted to the kernel.

Change-Id: Ifd44ab697bce5cd351f05069519785dc80e2b866
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 76a1c9cb3df930b28469608ecb5c35be7ccdadd1
Original-Change-Id: Ib09c813b49a4f00daca0b53d9dca972251fcf476
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/214773
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9017
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/arch/arm64/armv8/exception.c

@@ -127,11 +127,16 @@ static uint64_t test_exception(void)
 	return 0;
 }
 
-void exception_init(void)
+void exception_hwinit(void)
 {
 	extern void *exception_table;
-
 	set_vbar(&exception_table);
+}
+
+void exception_init(void)
+{
+	/* Load the exception table. */
+	exception_hwinit();
 
 	printk(BIOS_DEBUG, "ARM64: Exception handlers installed.\n");
 

src/arch/arm64/include/armv8/arch/exception.h

@@ -39,6 +39,8 @@ struct exception_state
 	uint64_t regs[31];
 } __attribute__((packed));
 
+/* Initialize the exception handling on the current CPU. */
+void exception_hwinit(void);
 void exception_init(void);
 void set_vbar(void *vbar);
 void exception_dispatch(struct exception_state *state, int idx);