Re: [PATCH v4 13/13] x86/hyperlaunch: add capabilities to boot domain

[dmkhn@proton.me]

On Thu, Apr 17, 2025 at 01:48:35PM +0100, Alejandro Vallejo wrote:
> From: "Daniel P. Smith" <dpsmith@apertussolutions.com>
> 
> Introduce the ability to assign capabilities to a domain via its definition in
> device tree. The first capability enabled to select is the control domain
> capability. The capability property is a bitfield in both the device tree and
> `struct boot_domain`.
> 
> Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
> Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
> Signed-off-by: Alejandro Vallejo <agarciav@amd.com>

Reviewed-by: Denis Mukhin <dmukhin@ford.com>

> ---
> v4:
>   * Dropped Jason's R-by.
>   * Refactored caps printinng logic
>     * It just wasn't xenlog-compatible as it was.
>   * Moved pv_shim check to builder_init, so the capability is just not given.
>     * And inlined the create_flags variable now that's tractable.
>   * Validated input capabilities after coming out of the DT.
> ---
>  xen/arch/x86/include/asm/boot-domain.h |  5 +++++
>  xen/arch/x86/setup.c                   |  3 ++-
>  xen/common/domain-builder/core.c       |  2 ++
>  xen/common/domain-builder/fdt.c        | 20 ++++++++++++++++++++
>  4 files changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/include/asm/boot-domain.h b/xen/arch/x86/include/asm/boot-domain.h
> index 969c02a6ea..5c143d82af 100644
> --- a/xen/arch/x86/include/asm/boot-domain.h
> +++ b/xen/arch/x86/include/asm/boot-domain.h
> @@ -13,6 +13,11 @@
>  struct boot_domain {
>      domid_t domid;
> 
> +#define BUILD_CAPS_NONE          (0U)
> +#define BUILD_CAPS_CONTROL       (1U << 0)
> +#define BUILD_CAPS__ALL          BUILD_CAPS_CONTROL
> +    uint32_t capabilities;
> +
>                                            /* On     | Off    */
>  #define BUILD_MODE_PARAVIRT      (1 << 0) /* PV     | PVH/HVM */
>  #define BUILD_MODE_ENABLE_DM     (1 << 1) /* HVM    | PVH     */
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 455dad454c..3cdd8bc2f9 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1040,7 +1040,8 @@ static struct domain *__init create_dom0(struct boot_info *bi)
>      if ( bd->domid == DOMID_INVALID )
>          /* Create initial domain.  Not d0 for pvshim. */
>          bd->domid = get_initial_domain_id();
> -    d = domain_create(bd->domid, &dom0_cfg, pv_shim ? 0 : CDF_privileged);
> +    d = domain_create(bd->domid, &dom0_cfg,
> +            (bd->capabilities & BUILD_CAPS_CONTROL) ? CDF_privileged : 0);
>      if ( IS_ERR(d) )
>          panic("Error creating d%u: %ld\n", bd->domid, PTR_ERR(d));
> 
> diff --git a/xen/common/domain-builder/core.c b/xen/common/domain-builder/core.c
> index 4b4230f2ff..d1a5d6125e 100644
> --- a/xen/common/domain-builder/core.c
> +++ b/xen/common/domain-builder/core.c
> @@ -8,6 +8,7 @@
>  #include <xen/lib.h>
> 
>  #include <asm/bootinfo.h>
> +#include <asm/pv/shim.h>
>  #include <asm/setup.h>
> 
>  #include "fdt.h"
> @@ -93,6 +94,7 @@ void __init builder_init(struct boot_info *bi)
> 
>          bi->mods[i].type = BOOTMOD_KERNEL;
>          bi->domains[0].kernel = &bi->mods[i];
> +        bi->domains[0].capabilities |= pv_shim ? 0 : BUILD_CAPS_CONTROL;
>          bi->nr_domains = 1;
>      }
>  }
> diff --git a/xen/common/domain-builder/fdt.c b/xen/common/domain-builder/fdt.c
> index 295ab6e8b3..3e3a84e2d0 100644
> --- a/xen/common/domain-builder/fdt.c
> +++ b/xen/common/domain-builder/fdt.c
> @@ -293,6 +293,26 @@ static int __init process_domain_node(
>              bd->max_vcpus = val;
>              printk(XENLOG_INFO "  cpus: %d\n", bd->max_vcpus);
>          }
> +        else if ( !strncmp(prop_name, "capabilities", name_len) )
> +        {
> +            if ( (rc = fdt_prop_as_u32(prop, &bd->capabilities)) )
> +            {
> +                printk(XENLOG_ERR
> +                       "  bad \"capabilities\" on domain %s\n", name);
> +                return rc;
> +            }
> +
> +            if ( bd->capabilities & ~BUILD_CAPS__ALL )
> +            {
> +                printk(XENLOG_WARNING "  unknown capabilities: %#x\n",
> +                       bd->capabilities & ~BUILD_CAPS__ALL);
> +
> +                bd->capabilities &= BUILD_CAPS__ALL;
> +            }
> +
> +            printk(XENLOG_INFO "  caps: %s\n",
> +                   bd->capabilities & BUILD_CAPS_CONTROL ? "c" : "");
> +        }
>      }
> 
>      fdt_for_each_subnode(node, fdt, dom_node)
> --
> 2.43.0
> 
>