Re: [PATCH v4 12/13] x86/hyperlaunch: add max vcpu parsing of hyperlaunch device tree

[dmkhn@proton.me]

On Thu, Apr 17, 2025 at 01:48:34PM +0100, Alejandro Vallejo wrote:
> From: "Daniel P. Smith" <dpsmith@apertussolutions.com>
> 
> Introduce the `cpus` property, named as such for dom0less compatibility, that
> represents the maximum number of vcpus to allocate for a domain. In the device
> tree, it will be encoded as a u32 value.
> 
> Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
> Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
> Signed-off-by: Alejandro Vallejo <agarciav@amd.com>

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

> ---
> v4:
>   * s/UINT_MAX/UINT32_MAX/ (cosmetic, but...)
>   * s/vpcpus/vcpus/ in commit message.
>   * Reworded printk()
> ---
>  xen/arch/x86/dom0_build.c              |  3 +++
>  xen/arch/x86/include/asm/boot-domain.h |  2 ++
>  xen/common/domain-builder/fdt.c        | 11 +++++++++++
>  3 files changed, 16 insertions(+)
> 
> diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c
> index 8db24dbc0a..f734104c74 100644
> --- a/xen/arch/x86/dom0_build.c
> +++ b/xen/arch/x86/dom0_build.c
> @@ -635,6 +635,9 @@ int __init construct_dom0(const struct boot_domain *bd)
>      if ( !get_memsize(&dom0_max_size, ULONG_MAX) && bd->max_pages )
>          dom0_max_size.nr_pages = bd->max_pages;
> 
> +    if ( opt_dom0_max_vcpus_max == UINT_MAX && bd->max_vcpus )
> +        opt_dom0_max_vcpus_max = bd->max_vcpus;
> +
>      if ( is_hvm_domain(d) )
>          rc = dom0_construct_pvh(bd);
>      else if ( is_pv_domain(d) )
> diff --git a/xen/arch/x86/include/asm/boot-domain.h b/xen/arch/x86/include/asm/boot-domain.h
> index fa8ea1cc66..969c02a6ea 100644
> --- a/xen/arch/x86/include/asm/boot-domain.h
> +++ b/xen/arch/x86/include/asm/boot-domain.h
> @@ -22,6 +22,8 @@ struct boot_domain {
>      unsigned long min_pages;
>      unsigned long max_pages;
> 
> +    unsigned int max_vcpus;
> +
>      struct boot_module *kernel;
>      struct boot_module *module;
>      const char *cmdline;
> diff --git a/xen/common/domain-builder/fdt.c b/xen/common/domain-builder/fdt.c
> index 90218d120a..295ab6e8b3 100644
> --- a/xen/common/domain-builder/fdt.c
> +++ b/xen/common/domain-builder/fdt.c
> @@ -282,6 +282,17 @@ static int __init process_domain_node(
>              bd->max_pages = PFN_DOWN(kb * SZ_1K);
>              printk(XENLOG_INFO "  max memory: %lu KiB\n", kb);
>          }
> +        else if ( !strncmp(prop_name, "cpus", name_len) )
> +        {
> +            uint32_t val = UINT32_MAX;
> +            if ( (rc = fdt_prop_as_u32(prop, &val)) )
> +            {
> +                printk(XENLOG_ERR "  bad \"cpus\" prop on domain %s\n", name);
> +                return rc;
> +            }
> +            bd->max_vcpus = val;
> +            printk(XENLOG_INFO "  cpus: %d\n", bd->max_vcpus);
> +        }
>      }
> 
>      fdt_for_each_subnode(node, fdt, dom_node)
> --
> 2.43.0
> 
>