Re: [PATCH v3 2/4] xen: make VMAP only support in MMU system

[Julien Grall <julien@xen.org>]

Hi Ayan,

On 19/08/2024 10:45, Ayan Kumar Halder wrote:
> I am ok with this. This has the benefit that the change can be contained 
> within arch/arm if we do the following :-
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index cb2c0a16b8..26f7406278 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -329,7 +329,9 @@ void asmlinkage __init start_xen(unsigned long 
> boot_phys_offset,
> 
>       setup_mm();
> 
> +#ifdef CONFIG_MMU
>       vm_init();
> +#endif
> 
>       /* Parse the ACPI tables for possible boot-time configuration */
>       acpi_boot_table_init();
> 
> Are we ok with this ?
> 
> The definition of vm_init() is in xen/include/xen/vmap.h. If I enclose 
> it using any CONFIG_XXX (like I have done in the current patch), then I 
> need to introduce it in common/Kconfig and define it for x86 and PPC. I 
> would prefer to contain the change within arch/arm only if possible.

Just to clarify, are you suggesting to just protect the call vm_init(). 
In other word, common/vmap.c would still be included in the final binary 
for the MPU?

If yes, then I think it would be a bit odd... Someone could still call 
vmap() and this would not break until runtime.

So I don't see how we could get away from modifying the common code.

Cheers,

-- 
Julien Grall