Re: [PATCH 4/6] xen: Allow hardare domain != dom0

[Julien Grall <julien.grall@linaro.org>]

Hello Daniel,

On 05/03/14 06:51, Daniel De Graaf wrote:
> This adds a hypervisor command line option "hardware_dom=" which takes a
> domain ID.  When the domain with this ID is created, it will be used as
> the hardware domain.
>
> This is intended to be used when dom0 is a dedicated stub domain for
> domain building, allowing the hardware domain to be de-privileged and
> act only as a driver domain.
>
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Cc: Keir Fraser <keir@xen.org>
> Cc: Jan Beulich <jbeulich@suse.com>
> ---
>   xen/arch/x86/domain_build.c |  4 +++-
>   xen/arch/x86/setup.c        |  3 +++
>   xen/common/domctl.c         |  8 ++++++++
>   xen/common/rangeset.c       | 26 ++++++++++++++++++++++++++
>   xen/include/xen/rangeset.h  |  3 +++
>   xen/include/xen/sched.h     |  3 ++-
>   6 files changed, 45 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/x86/domain_build.c b/xen/arch/x86/domain_build.c
> index 84ce392..e9de496 100644
> --- a/xen/arch/x86/domain_build.c
> +++ b/xen/arch/x86/domain_build.c
> @@ -1149,7 +1149,9 @@ int __init construct_dom0(
>           printk(" Xen warning: dom0 kernel broken ELF: %s\n",
>                  elf_check_broken(&elf));
>
> -    iommu_dom0_init(dom0);
> +    if( is_hardware_domain(dom0) )
> +        iommu_dom0_init(dom0);
> +
>       return 0;
>
>   out:
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 3a4f69c..3480854 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -88,6 +88,9 @@ unsigned long __initdata highmem_start;
>   size_param("highmem-start", highmem_start);
>   #endif
>
> +unsigned int __read_mostly hardware_dom;
> +integer_param("hardware_dom", hardware_dom);
> +
>   cpumask_t __read_mostly cpu_present_map;
>
>   unsigned long __read_mostly xen_phys_start;
> diff --git a/xen/common/domctl.c b/xen/common/domctl.c
> index eebeee7..11e6b94 100644
> --- a/xen/common/domctl.c
> +++ b/xen/common/domctl.c
> @@ -472,6 +472,14 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
>               break;
>           }
>
> +        if (d->domain_id == hardware_dom) {
> +            printk("Initialising hardware domain %d\n", hardware_dom);
> +            rangeset_swap(d->irq_caps, dom0->irq_caps);
> +
> +            dom0 = d;
> +            iommu_dom0_init(dom0);
> +        }
> +

This patch will break compilation on ARM. You are using hardware_dom 
which is defined in xen/arch/x86/setup.c.

I'm not sure if the best solution is to move the defined for 
hardware_dom in common code ... because settings this variable to a 
value other than 0 will break ARM boot with your changes in patch #1.

Supporting hardware domain on ARM will need rework on dom0 builder.

Regards,

-- 
Julien Grall