From: Julien Grall <jgrall@amazon.com>

Since commit 54c4ae18d158 ("xen/arm32: head: Rework and document
launch()"), the boot code is setting r12 but not read it.

So remove the two instructions setting r12 and update the documentation
to show r12 has no specific purpose.

Signed-off-by: Julien Grall <jgrall@amazon.com>

---
    Changes in v2:
        - Don't set r12.
---
 xen/arch/arm/arm32/head.S | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 13cfc837d39c..7a906167efca 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -79,7 +79,7 @@
  *   r9  - paddr(start)
  *   r10 - phys offset
  *   r11 - UART address
- *   r12 - is_secondary_cpu
+ *   r12 -
  *   r13 - SP
  *   r14 - LR
  *   r15 - PC
@@ -166,8 +166,6 @@ past_zImage:
 #endif
         PRINT("- Boot CPU booting -\r\n")
 
-        mov   r12, #0                /* r12 := is_secondary_cpu */
-
         bl    check_cpu_mode
         bl    cpu_init
         bl    create_page_tables
@@ -206,8 +204,6 @@ GLOBAL(init_secondary)
         adr   r9, start              /* r9  := paddr (start) */
         sub   r10, r9, r0            /* r10 := phys-offset */
 
-        mov   r12, #1                /* r12 := is_secondary_cpu */
-
         mrc   CP32(r1, MPIDR)
         bic   r7, r1, #(~MPIDR_HWID_MASK) /* Mask out flags to get CPU ID */
 
-- 
2.32.0

Hi Julien,

> On 28 Feb 2022, at 13:35, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> Since commit 54c4ae18d158 ("xen/arm32: head: Rework and document
> launch()"), the boot code is setting r12 but not read it.
> 
> So remove the two instructions setting r12 and update the documentation
> to show r12 has no specific purpose.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Cheers
Bertrand

> 
> ---
>    Changes in v2:
>        - Don't set r12.
> ---
> xen/arch/arm/arm32/head.S | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 13cfc837d39c..7a906167efca 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -79,7 +79,7 @@
>  *   r9  - paddr(start)
>  *   r10 - phys offset
>  *   r11 - UART address
> - *   r12 - is_secondary_cpu
> + *   r12 -
>  *   r13 - SP
>  *   r14 - LR
>  *   r15 - PC
> @@ -166,8 +166,6 @@ past_zImage:
> #endif
>         PRINT("- Boot CPU booting -\r\n")
> 
> -        mov   r12, #0                /* r12 := is_secondary_cpu */
> -
>         bl    check_cpu_mode
>         bl    cpu_init
>         bl    create_page_tables
> @@ -206,8 +204,6 @@ GLOBAL(init_secondary)
>         adr   r9, start              /* r9  := paddr (start) */
>         sub   r10, r9, r0            /* r10 := phys-offset */
> 
> -        mov   r12, #1                /* r12 := is_secondary_cpu */
> -
>         mrc   CP32(r1, MPIDR)
>         bic   r7, r1, #(~MPIDR_HWID_MASK) /* Mask out flags to get CPU ID */
> 
> -- 
> 2.32.0
> 
> 

Hi Julien,

On 28.02.2022 14:35, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> Since commit 54c4ae18d158 ("xen/arm32: head: Rework and document
> launch()"), the boot code is setting r12 but not read it.
> 
> So remove the two instructions setting r12 and update the documentation
> to show r12 has no specific purpose.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> ---
>     Changes in v2:
>         - Don't set r12.
> ---

Reviewed-by: Michal Orzel <michal.orzel@arm.com>

Cheers,
Michal