Re: [XEN PATCH v2 3/5] xen/arm: configure dom0less domain for enabling xenstore after boot

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Stefano,

+ Penny in CC for the question.

> On 13 Jan 2022, at 00:58, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> 
> From: Luca Miccio <lucmiccio@xxxxxxxxx>
> 
> If "xen,enhanced" is enabled, then add to dom0less domains:
> 
> - the hypervisor node in device tree
> - the xenstore event channel
> 
> The xenstore event channel is also used for the first notification to
> let the guest know that xenstore has become available.
> 
> Signed-off-by: Luca Miccio <lucmiccio@xxxxxxxxx>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> CC: Julien Grall <julien@xxxxxxx>
> CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Just one question: GUEST_GNTTAB_BASE is fixed but could it be a problem for a 
direct map guest in the future ?

Regards
Bertrand

> 
> ---
> Changes in v2:
> - set HVM_PARAM_STORE_PFN to ~0ULL at domain creation
> - in alloc_xenstore_evtchn do not call _evtchn_alloc_unbound
> ---
> xen/arch/arm/domain_build.c | 43 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 9144d6c0b6..251d933c8e 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -27,6 +27,7 @@
> #include <asm/setup.h>
> #include <asm/cpufeature.h>
> #include <asm/domain_build.h>
> +#include <xen/event.h>
> 
> #include <xen/irq.h>
> #include <xen/grant_table.h>
> @@ -2619,6 +2620,8 @@ static int __init prepare_dtb_domU(struct domain *d, 
> struct kernel_info *kinfo)
>     int ret;
> 
>     kinfo->phandle_gic = GUEST_PHANDLE_GIC;
> +    kinfo->gnttab_start = GUEST_GNTTAB_BASE;
> +    kinfo->gnttab_size = GUEST_GNTTAB_SIZE;
> 
>     addrcells = GUEST_ROOT_ADDRESS_CELLS;
>     sizecells = GUEST_ROOT_SIZE_CELLS;
> @@ -2693,6 +2696,13 @@ static int __init prepare_dtb_domU(struct domain *d, 
> struct kernel_info *kinfo)
>             goto err;
>     }
> 
> +    if ( kinfo->dom0less_enhanced )
> +    {
> +        ret = make_hypervisor_node(d, kinfo, addrcells, sizecells);
> +        if ( ret )
> +            goto err;
> +    }
> +
>     ret = fdt_end_node(kinfo->fdt);
>     if ( ret < 0 )
>         goto err;
> @@ -2959,6 +2969,27 @@ static int __init construct_domain(struct domain *d, 
> struct kernel_info *kinfo)
>     return 0;
> }
> 
> +static int __init alloc_xenstore_evtchn(struct domain *d)
> +{
> +    struct evtchn *chn;
> +    int port;
> +
> +    if ( (port = get_free_port(d)) < 0 )
> +    {
> +        printk("Failed allocating event channel for domain\n");
> +        return port;
> +    }
> +    chn = evtchn_from_port(d, port);
> +
> +    chn->state = ECS_UNBOUND;
> +    chn->u.unbound.remote_domid = hardware_domain->domain_id;
> +    evtchn_port_init(d, chn);
> +
> +    d->arch.hvm.params[HVM_PARAM_STORE_EVTCHN] = chn->port;
> +
> +    return 0;
> +}
> +
> static int __init construct_domU(struct domain *d,
>                                  const struct dt_device_node *node)
> {
> @@ -3014,7 +3045,19 @@ static int __init construct_domU(struct domain *d,
>         return rc;
> 
>     if ( kinfo.vpl011 )
> +    {
>         rc = domain_vpl011_init(d, NULL);
> +        if ( rc < 0 )
> +            return rc;
> +    }
> +
> +    if ( kinfo.dom0less_enhanced )
> +    {
> +        rc = alloc_xenstore_evtchn(d);
> +        if ( rc < 0 )
> +            return rc;
> +        d->arch.hvm.params[HVM_PARAM_STORE_PFN] = ~0ULL;
> +    }
> 
>     return rc;
> }
> -- 
> 2.25.1
>