Re: [PATCH v3 1/7] xen: introduce hardware domain create flag

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 3 Apr 2025, Jason Andryuk wrote:
> From: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> 
> Add and use a new internal create domain flag to specify the hardware
> domain.  This removes the hardcoding of domid 0 as the hardware domain.
> 
> This allows more flexibility with domain creation.
> 
> Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

ARM:
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> v3:
> Or-in CDF_hardware for late hwdom case
> Add Jan's R-b
> 
> v2:
> () around binary &
> Only allow late_hwdom for dom0
> ---
>  xen/arch/arm/domain_build.c | 2 +-
>  xen/arch/x86/setup.c        | 3 ++-
>  xen/common/domain.c         | 7 ++++++-
>  xen/include/xen/domain.h    | 2 ++
>  4 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 634333cdde..b8f282ff10 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -2369,7 +2369,7 @@ void __init create_dom0(void)
>          .max_maptrack_frames = -1,
>          .grant_opts = XEN_DOMCTL_GRANT_version(opt_gnttab_max_version),
>      };
> -    unsigned int flags = CDF_privileged;
> +    unsigned int flags = CDF_privileged | CDF_hardware;
>      int rc;
>  
>      /* The vGIC for DOM0 is exactly emulating the hardware GIC */
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index d70abb7e0c..67d399c469 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1018,7 +1018,8 @@ static struct domain *__init create_dom0(struct 
> boot_info *bi)
>  
>      /* Create initial domain.  Not d0 for pvshim. */
>      domid = get_initial_domain_id();
> -    d = domain_create(domid, &dom0_cfg, pv_shim ? 0 : CDF_privileged);
> +    d = domain_create(domid, &dom0_cfg,
> +                      pv_shim ? 0 : CDF_privileged | CDF_hardware);
>      if ( IS_ERR(d) )
>          panic("Error creating d%u: %ld\n", domid, PTR_ERR(d));
>  
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index 585fd726a9..da74f815f4 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -820,13 +820,18 @@ struct domain *domain_create(domid_t domid,
>      d->is_privileged = flags & CDF_privileged;
>  
>      /* Sort out our idea of is_hardware_domain(). */
> -    if ( domid == 0 || domid == hardware_domid )
> +    if ( (flags & CDF_hardware) || domid == hardware_domid )
>      {
>          if ( hardware_domid < 0 || hardware_domid >= DOMID_FIRST_RESERVED )
>              panic("The value of hardware_dom must be a valid domain ID\n");
>  
> +        /* late_hwdom is only allowed for dom0. */
> +        if ( hardware_domain && hardware_domain->domain_id )
> +            return ERR_PTR(-EINVAL);
> +
>          old_hwdom = hardware_domain;
>          hardware_domain = d;
> +        flags |= CDF_hardware;
>      }
>  
>      TRACE_TIME(TRC_DOM0_DOM_ADD, d->domain_id);
> diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
> index a34daa7d10..e10baf2615 100644
> --- a/xen/include/xen/domain.h
> +++ b/xen/include/xen/domain.h
> @@ -53,6 +53,8 @@ domid_t get_initial_domain_id(void);
>  #else
>  #define CDF_staticmem            0
>  #endif
> +/* This is the hardware domain.  Only 1 allowed. */
> +#define CDF_hardware             (1U << 3)
>  
>  #define is_domain_direct_mapped(d) ((d)->cdf & CDF_directmap)
>  #define is_domain_using_staticmem(d) ((d)->cdf & CDF_staticmem)
> -- 
> 2.49.0
>