Re: [PATCH 04/23] xen/arm: dom0less use domid 0 for hwdom

[Julien Grall <julien@xxxxxxx>]

Hi,

On 06/03/2025 22:03, Jason Andryuk wrote:
> Assign domid 0 to the hwdom.  Normally, dom0less does not use domid 0.
A few years ago, we went to great length to avoid making the assumption 
that the hardware domain is domid 0. See all the calls to 
"is_hardware_domain()". So I am reluctant to force the domain ID to 0.
> This fixes using the Xen console which assumes domid 0 to use the
> hypercall interface.
I had a brief look at drivers/char/console.c and I can't find any place 
assuming "domid 0". Do you have any pointer?
> Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
> ---
>   xen/arch/arm/dom0less-build.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
> index e539bcc762..5a7871939b 100644
> --- a/xen/arch/arm/dom0less-build.c
> +++ b/xen/arch/arm/dom0less-build.c
> @@ -969,6 +969,7 @@ void __init create_domUs(void)
>       dt_for_each_child_node(chosen, node)
>       {
>           struct domain *d;
> +        domid_t domid;
>           struct xen_domctl_createdomain d_cfg = {
>               .arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE,
>               .flags = XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap,
> @@ -1121,7 +1122,12 @@ void __init create_domUs(void)
>            * very important to use the pre-increment operator to call
>            * domain_create() with a domid > 0. (domid == 0 is reserved for Dom0)
>            */
> -        d = domain_create(++max_init_domid, &d_cfg, flags);
> +        if ( flags & CDF_hardware )
> +            domid = 0;
> +        else
> +            domid = ++max_init_domid;
> +
> +        d = domain_create(domid, &d_cfg, flags);
>           if ( IS_ERR(d) )
>               panic("Error creating domain %s (rc = %ld)\n",
>                     dt_node_name(node), PTR_ERR(d));
Cheers,

--
Julien Grall