Re: [PATCH v1 4/8] xen/domain: introduce domid_alloc()

[Jan Beulich <jbeulich@suse.com>]

On 19.03.2025 00:36, dmkhn@proton.me wrote:
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -2367,8 +2367,15 @@ void __init create_dom0(void)
>          .grant_opts = XEN_DOMCTL_GRANT_version(opt_gnttab_max_version),
>      };
>      unsigned int flags = CDF_privileged;
> +    domid_t domid;
>      int rc;
>  
> +    rc = domid_alloc(get_initial_domain_id());
> +    if ( rc < 0 )
> +        panic("Cannot use domain ID %d (rc = %d)\n",
> +              get_initial_domain_id(), rc);
> +    domid = rc;
> +
>      /* The vGIC for DOM0 is exactly emulating the hardware GIC */
>      dom0_cfg.arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE;
>      dom0_cfg.arch.nr_spis = VGIC_DEF_NR_SPIS;
> @@ -2391,19 +2398,21 @@ void __init create_dom0(void)
>      if ( !llc_coloring_enabled )
>          flags |= CDF_directmap;
>  
> -    dom0 = domain_create(0, &dom0_cfg, flags);
> +    dom0 = domain_create(domid, &dom0_cfg, flags);
>      if ( IS_ERR(dom0) )
> -        panic("Error creating domain 0 (rc = %ld)\n", PTR_ERR(dom0));
> +        panic("Error creating domain %d (rc = %ld)\n", domid, PTR_ERR(dom0));
>  
>      if ( llc_coloring_enabled && (rc = dom0_set_llc_colors(dom0)) )
> -        panic("Error initializing LLC coloring for domain 0 (rc = %d)\n", rc);
> +        panic("Error initializing LLC coloring for domain %d (rc = %d)\n",
> +              domid, rc);
>  
>      if ( alloc_dom0_vcpu0(dom0) == NULL )
> -        panic("Error creating domain 0 vcpu0\n");
> +        panic("Error creating domain %d vcpu0\n", domid);
>  
>      rc = construct_dom0(dom0);
>      if ( rc )
> -        panic("Could not set up DOM0 guest OS (rc = %d)\n", rc);
> +        panic("Could not set up guest OS for domain %d (rc = %d)\n",
> +              domid, rc);
>  }

Assuming we really needed this new function, why would there be an Arm side
change to Dom0 creation, but no equivalent change on the x86 side?

Jan