xen/arm64: head: Don't set x22 and update the documentation

Since commit 7e14a47e7c73 ("xen/arm64: head Rework and document
launch()"), the boot code is setting x22 but not read it.

So remove the two instructions setting x22 and update the documentation
to show x22 has no specific purpose.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Reviewed-by: Wei Chen <Wei.Chen@arm.com>

diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 1babcc65d7c9ccd0c6ecec4b52ffbae0ba11d2a4..26cc7705f556fe45aea7278eb0121587de1c72b9 100644 (file)
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -71,7 +71,7 @@
  *  x19 - paddr(start)
  *  x20 - phys offset
  *  x21 - DTB address (boot cpu only)
- *  x22 - is_secondary_cpu
+ *  x22 -
  *  x23 - UART address
  *  x24 -
  *  x25 -
@@ -305,8 +305,6 @@ real_start_efi:
 #endif
         PRINT("- Boot CPU booting -\r\n")
 
-        mov   x22, #0                /* x22 := is_secondary_cpu */
-
         bl    check_cpu_mode
         bl    cpu_init
         bl    create_page_tables
@@ -345,8 +343,6 @@ GLOBAL(init_secondary)
         adr   x19, start             /* x19 := paddr (start) */
         sub   x20, x19, x0           /* x20 := phys-offset */
 
-        mov   x22, #1                /* x22 := is_secondary_cpu */
-
         mrs   x0, mpidr_el1
         ldr   x13, =(~MPIDR_HWID_MASK)
         bic   x24, x0, x13           /* Mask out flags to get CPU ID */