Re: [PATCH v2 14/17] tools/xenstored: Auto-introduce domains

[Juergen Gross <jgross@xxxxxxxx>]

On 16.07.25 23:15, Jason Andryuk wrote:
> Replace dom0_init() with init_domains() which uses libxenmanage to
> iterate through all existing domains and introduce them.
>
> dom0_domid is updated with the xenstore domain, since it really
> indicates the local domain.
I agree with that explanation, but I wonder whether this explanation
doesn't indicate that a rename of the dom0_domid variable is wanted,
e.g. to "store_domid".

> priv_domid is set to the control domain.  This makes it limited to a
> single domain.
Maybe another candidate for renaming (ctrl_domid?).

> These features let xenstore automatically connect any existing domains,
> which means it doesn't need to be done manually from init-dom0less.
>
> For a legacy dom0, the result should be unchanged.
>
> For a late xenstore stubdom it should also be the same, but priv_domid
> would be set automatically to control domain (which default to 0
> normally).
>
> Always signal the event channel for initial domains.  This gets dom0 (a
> local xenstored domain) to connect.
>
> Also always write XENSTORE_CONNECTED since we know we are connected at
> this point.
>
> Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
> ---
>   tools/xenstored/core.c   |  2 +-
>   tools/xenstored/domain.c | 45 +++++++++++++++++++++++++++++++---------
>   tools/xenstored/domain.h |  2 +-
>   3 files changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/tools/xenstored/core.c b/tools/xenstored/core.c
> index 550e879a00..835402af81 100644
> --- a/tools/xenstored/core.c
> +++ b/tools/xenstored/core.c
> @@ -2762,7 +2762,7 @@ int main(int argc, char *argv[])
>         /* Listen to hypervisor. */
>         if (!live_update) {
>                 domain_init(-1);
> -               dom0_init();
> +               init_domains();
>         }
>   
>   	/* redirect to /dev/null now we're ready to accept connections */
> diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
> index 5443b4e608..44e997cee4 100644
> --- a/tools/xenstored/domain.c
> +++ b/tools/xenstored/domain.c
> @@ -1257,20 +1257,45 @@ const char *get_implicit_path(const struct connection 
> *conn)
>         return conn->domain->path;
>   }
>   
> -void dom0_init(void)
> +void init_domains(void)
>   {
> -       evtchn_port_t port;
> -       struct domain *dom0;
> +       unsigned int domid;
> +       unsigned int state;
> +       unsigned int caps;
> +       uint64_t unique_id;
> +
> +       while (!xenmanage_poll_changed_domain(xm_handle, &domid, &state, &caps,
> +                                             &unique_id)) {
> +               evtchn_port_t port = 0;
> +               struct domain *domain;
> +
> +               if (caps & XENMANAGE_GETDOMSTATE_CAP_XENSTORE)
> +                       dom0_domid = domid;
> +
> +               if (caps & XENMANAGE_GETDOMSTATE_CAP_CONTROL)
> +                       priv_domid = domid;
>   
> -	port = get_xenbus_evtchn();
> -       if (port == -1)
> -               barf_perror("Failed to initialize dom0 port");
> +               if (domid == dom0_domid) {
> +                       port = get_xenbus_evtchn();
> +                       if (port == -1)
> +                               barf_perror("Failed to initialize dom%u port",
> +                                           domid);
> +               }
I don't think this is correct for a xenstore-stubdom. See stubdom_init().

> +
> +               domain = introduce_domain(NULL, domid, port, false);
> +               if (!domain) {
> +                       xprintf("Could not initialize dom%u", domid);
> +                       continue;
> +               }
>   
> -	dom0 = introduce_domain(NULL, xenbus_master_domid(), port, false);
> -       if (!dom0)
> -               barf_perror("Failed to initialize dom0");
> +               domain_conn_reset(domain);
>   
> -	xenevtchn_notify(xce_handle, dom0->port);
> +               if (domain->interface)
> +                       domain->interface->connection = XENSTORE_CONNECTED;
> +
> +               /* Notify the domain that xenstore is available */
> +               xenevtchn_notify(xce_handle, domain->port);
> +       }
>   }
>   
>   void stubdom_init(void)
> diff --git a/tools/xenstored/domain.h b/tools/xenstored/domain.h
> index 844ac11510..6a78f06935 100644
> --- a/tools/xenstored/domain.h
> +++ b/tools/xenstored/domain.h
> @@ -84,7 +84,7 @@ int do_reset_watches(const void *ctx, struct connection *conn,
>   
>   void domain_early_init(void);
>   void domain_init(int evtfd);
> -void dom0_init(void);
> +void init_domains(void);
>   void stubdom_init(void);
>   void domain_deinit(void);
>   void ignore_connection(struct connection *conn, unsigned int err);

Juergen

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