[boot-wrapper PATCH v2 5/8] aarch64: Prepare for lower EL booting

[Andre Przywara]

On Fri, 21 May 2021 18:48:04 +0800
Jaxson Han <jaxson.han at arm.com> wrote:

Hi,

> Save SPSR_KERNEL into spsr_to_elx during el3_init.
> The jump_kernel will load spsr_to_elx into spsr_el3.
> 
> This change will make it easier to control whether drop to lower EL
> before jumping to the kernel.

Looks good, but this needs some adaption after fixing patch 2/8:

> 
> Signed-off-by: Jaxson Han <jaxson.han at arm.com>
> ---
>  arch/aarch64/boot.S | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
> index b8f9e4e..5600859 100644
> --- a/arch/aarch64/boot.S
> +++ b/arch/aarch64/boot.S
> @@ -118,7 +118,16 @@ el3_init:
>  	mov	x0, #ZCR_EL3_LEN_MASK		// SVE: Enable full vector len
>  	msr	ZCR_EL3, x0			// for EL2.
>  
> -1:
> +	/*
> +	 * Save SPSR_KERNEL into spsr_to_elx.
> +	 * The jump_kernel will load spsr_to_elx into spsr_el3
> +	 */
> +1:	mov	w0, #SPSR_KERNEL
> +	ldr	x1, =spsr_to_elx
> +	str	w0, [x1]
> +	b	el_max_init
> +
> +el_max_init:
>  	ldr	x0, =CNTFRQ
>  	msr	cntfrq_el0, x0
>  
> @@ -166,7 +175,7 @@ jump_kernel:
>  	b.eq	1f
>  	br	x19			// Keep current EL
>  
> -1:	ldr	w4, #SPSR_KERNEL
> +1:	ldr	w4, spsr_to_elx

This would be the place where you change the original "mov x4,
#SPSR_KERNEL" line into this one here (and not in patch 2).

With that fixed:

Reviewed-by: Andre Przywara <andre.przywara at arm.com>

Cheers,
Andre

>  
>  	/*
>  	 * If bit 0 of the kernel address is set, we're entering in AArch32
> @@ -184,3 +193,5 @@ jump_kernel:
>  	.align 3
>  flag_keep_el:
>  	.long 0
> +spsr_to_elx:
> +	.long 0