Re: [PATCH v1 4/4] xen/arm: mpu: Disable secondary cpu bringup

[Julien Grall <julien@xxxxxxx>]

Hi Ayan,

The title is a bit confusing. It implies seconary CPU bringup used to 
work on the MPU. However, you are adding a stub for enable_secondary_cpu_mm.
Also, I am not entirely this is really sufficient to disable CPU 
bringup. There will be plenty of initialization done for secondary CPUs.
I would suggest to update NR_CPUS to 1 for MPU so we will fail early.

For the title, how about

xen/arm: mpu: Implement a dummy enable_secondary_cpu_mm

On 23/08/2024 17:31, Ayan Kumar Halder wrote:
> Secondary cpus are put in WFE state. We do not support SMP at this time.
>
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> ---
>   xen/arch/arm/arm64/mpu/head.S | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/xen/arch/arm/arm64/mpu/head.S b/xen/arch/arm/arm64/mpu/head.S
> index 2b023c346a..1579ac0408 100644
> --- a/xen/arch/arm/arm64/mpu/head.S
> +++ b/xen/arch/arm/arm64/mpu/head.S
> @@ -68,3 +68,12 @@ ENTRY(enable_boot_cpu_mm)
>   
>       ret
>   ENDPROC(enable_boot_cpu_mm)
> +
> +/*
> + * Secondary cpu has not yet been supported on MPU systems. We will block the
> + * secondary cpu bringup at this stage.
> + */
> +ENTRY(enable_secondary_cpu_mm)
Can we print a message so it is easier to spot that 
enable_secondary_cpu_mm is not properly implemented?
> +1:  wfe
> +    b 1b
> +ENDPROC(enable_secondary_cpu_mm)
Cheers,

--
Julien Grall