On Mon, 31 Mar 2025, Jason Andryuk wrote:
> To allocate the xenstore event channel and initialize the grant table
> entry, the xenstore domid is neeed. A dom0 is created before the domUs,
> so it is normally available through hardware_domain. With capabilities
> and dom0less, the xenstore domain may not be created first.
>
> Keep the population of the page and HVM_PARAM_STORE_PFN in the normal
> domain construction, but delay event channel creation and grant seeding
> to after all domUs are created. HVM_PARAM_STORE_PFN now serves as
> indication to setup xenstore since the device tree is no longer
> immediately available. 0 means no xenstore. ~0ULL means legacy so only
> the event channel needs setup, and any other value means to seed the
> page.
>
> dom0 needs to set xs_domid when it is serving as the xenstore domain.
>
> The domain running xenstored needs to be the handler for VIRQ_DOM_EXC,
> so set that as well - it otherwise defaults to hardware domain.
>
> Signed-off-by: Jason Andryuk <jason.andr...@amd.com>
> ---
> v2:
> Re-order ahead of seeding.
> Fix created type in commit message
> Change set_xs_domid to set_xs_domain
> Set xenstore domain as VIRQ_DOM_EXC handler
>
> Signed-off-by: Jason Andryuk <jason.andr...@amd.com>
> ---
> xen/arch/arm/dom0less-build.c | 67 +++++++++++++++++------
> xen/arch/arm/domain_build.c | 2 +
> xen/arch/arm/include/asm/dom0less-build.h | 2 +
> 3 files changed, 53 insertions(+), 18 deletions(-)
>
> diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
> index e25d7bd468..a46f292c1f 100644
> --- a/xen/arch/arm/dom0less-build.c
> +++ b/xen/arch/arm/dom0less-build.c
> @@ -20,6 +20,15 @@
> #include <asm/static-memory.h>
> #include <asm/static-shmem.h>
>
> +static domid_t __initdata xs_domid = DOMID_INVALID;
> +static bool __initdata need_xenstore;
> +
> +void __init set_xs_domain(struct domain *d)
> +{
> + xs_domid = d->domain_id;
> + set_global_virq_handler(d, VIRQ_DOM_EXC);
> +}
> +
> bool __init is_dom0less_mode(void)
> {
> struct bootmodules *mods = &bootinfo.modules;
> @@ -694,7 +703,7 @@ static int __init alloc_xenstore_evtchn(struct domain *d)
> int rc;
>
> alloc.dom = d->domain_id;
> - alloc.remote_dom = hardware_domain->domain_id;
> + alloc.remote_dom = xs_domid;
> rc = evtchn_alloc_unbound(&alloc, 0);
> if ( rc )
> {
> @@ -760,16 +769,10 @@ static int __init alloc_xenstore_params(struct
> kernel_info *kinfo)
> struct domain *d = kinfo->d;
> int rc = 0;
>
> - if ( kinfo->dom0less_feature & (DOM0LESS_XENSTORE | DOM0LESS_XS_LEGACY) )
> - {
> - ASSERT(hardware_domain);
> - rc = alloc_xenstore_evtchn(d);
> - if ( rc < 0 )
> - return rc;
> + if ( (kinfo->dom0less_feature & (DOM0LESS_XENSTORE | DOM0LESS_XS_LEGACY))
> + == (DOM0LESS_XENSTORE | DOM0LESS_XS_LEGACY)
> )
> d->arch.hvm.params[HVM_PARAM_STORE_PFN] = ~0ULL;
> - }
> -
> - if ( kinfo->dom0less_feature & DOM0LESS_XENSTORE )
> + else if ( kinfo->dom0less_feature & DOM0LESS_XENSTORE )
> {
> rc = alloc_xenstore_page(d);
> if ( rc < 0 )
> @@ -841,6 +844,30 @@ static void __init domain_vcpu_affinity(struct domain *d,
> }
> }
>
> +static void __init initialize_domU_xenstore(void)
> +{
> + struct domain *d;
> +
> + if ( xs_domid == DOMID_INVALID )
> + return;
> +
> + for_each_domain( d )
> + {
> + unsigned long gfn = d->arch.hvm.params[HVM_PARAM_STORE_PFN];
This should be uint64_t. With that change:
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
> + int rc;
> +
> + if ( gfn == 0 )
> + continue;
> +
> + if ( is_xenstore_domain(d) )
> + continue;
> +
> + rc = alloc_xenstore_evtchn(d);
> + if ( rc < 0 )
> + panic("%pd: Failed to allocate xenstore_evtchn\n", d);
> + }
> +}
> +
> static int __init construct_domU(struct domain *d,
> const struct dt_device_node *node)
> {
