Re: [RFC PATCH] xen/kconfig: allow LATE_HWDOM config for ARM

[Julien Grall <julien@xxxxxxx>]

Hi,

Can you clarify why this is an RFC?

On 17/12/2024 11:47, Sergiy Kibrik wrote:
> Allow to build ARM configuration with support for initializing hardware domain.
> On ARM it is only possible to start hardware domain in multiboot mode, so
> dom0less support is required. This is reflected by dependency on DOM0LESS_BOOT
> instead of directly depending on ARM config option.
I am a bit confused with the explanation. We already have an hardware 
domain on Arm. It is dom0. So what are you trying to achieve? Is this 
remove some permissions from the hardware domain?
If so, why can't the hardware domain stay as dom0 and you remove the 
feature you don't want (e.g. control domain)?
Are you sure this patch is sufficient to use the late hwdom feature? 
Looking at the code, to enable the late hwdom, the user needs to provide 
a domid on the command line. But AFAICT, there is no way to provide a 
domain ID in the DOM0LESS case...
> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
> ---
>   xen/common/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> index 90268d9249..7368ca8208 100644
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -374,7 +374,7 @@ endchoice
>   config LATE_HWDOM
>         bool "Dedicated hardware domain"
>         default n
> -       depends on XSM && X86
> +       depends on XSM && (X86 || DOM0LESS_BOOT)
This will enable LATE_HWDOM for other arch. Is this what we want?

>         help
>           Allows the creation of a dedicated hardware domain distinct from
>           domain 0 that manages devices without needing access to other
Cheers,

--
Julien Grall