Re: [PATCH 4/7] tools/xenstored: add server feature support

[Juergen Gross <jgross@xxxxxxxx>]

On 25.07.25 07:18, Jürgen Groß wrote:
> On 25.07.25 00:48, Jason Andryuk wrote:
> > On 2025-07-22 10:06, Juergen Gross wrote:
> > > Add per domain server features, which are initialized by the supported
> > > features at domain introduction, or by live update from the migration
> > > stream. This requires to add the DOMAIN_DATA record to the migration
> > > stream, but for now it will only contain the feature word.
> > >
> > > Advertise the Xenstore features to guests by setting the appropriate
> > > bits in the ring page.
> > >
> > > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > > ---
> > >   tools/xenstored/domain.c | 71 ++++++++++++++++++++++++++++++++++++----
> > >   tools/xenstored/domain.h |  3 ++
> > >   tools/xenstored/lu.c     | 14 ++++++--
> > >   tools/xenstored/lu.h     |  2 +-
> > >   4 files changed, 80 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
> > > index e1d5e8d614..f6d24bc13a 100644
> > > --- a/tools/xenstored/domain.c
> > > +++ b/tools/xenstored/domain.c
> > > @@ -32,6 +32,7 @@
> > >   #include "transaction.h"
> > >   #include "watch.h"
> > >   #include "control.h"
> > > +#include "lu.h"
> > >   #include <xenevtchn.h>
> > >   #include <xenmanage.h>
> > > @@ -42,6 +43,8 @@
> > >   #include <mini-os/xenbus.h>
> > >   #endif
> > > +#define XENSTORE_FEATURES    XENSTORE_SERVER_FEATURE_ERROR
> > > +
> > >   static xenmanage_handle *xm_handle;
> > >   xengnttab_handle **xgt_handle;
> > >   static evtchn_port_t virq_port;
> > > @@ -115,6 +118,9 @@ struct domain
> > >       /* Event channel port */
> > >       evtchn_port_t port;
> > > +    /* Server features supported for this domain. */
> > > +    unsigned int features;
> > > +
> > >       /* Domain path in store. */
> > >       char *path;
> > > @@ -799,6 +805,7 @@ static struct domain *alloc_domain(const void *context, 
> > > unsigned int domid,
> > >       domain->unique_id = unique_id;
> > >       domain->generation = generation;
> > >       domain->introduced = false;
> > > +    domain->features = XENSTORE_FEATURES;
> > >       if (hashtable_add(domhash, &domain->domid, domain)) {
> > >           talloc_free(domain);
> > > @@ -992,7 +999,8 @@ void ignore_connection(struct connection *conn, unsigned 
> > > int err)
> > >   {
> > >       trace("CONN %p ignored, reason %u\n", conn, err);
> > > -    if (conn->domain && conn->domain->interface)
> > > +    if (conn->domain && conn->domain->interface &&
> > > +        (conn->domain->features & XENSTORE_SERVER_FEATURE_ERROR))
> > >           conn->domain->interface->error = err;
> > >       conn->is_ignored = true;
> > > @@ -1078,11 +1086,14 @@ int do_introduce(const void *ctx, struct connection 
> > > *conn,
> > >       domain_conn_reset(domain);
> > > -    if (domain->interface != NULL &&
> > > -        domain->interface->connection == XENSTORE_RECONNECT) {
> > > -        /* Notify the domain that xenstore is available */
> > > -        domain->interface->connection = XENSTORE_CONNECTED;
> > > -        xenevtchn_notify(xce_handle, domain->port);
> > > +    if (domain->interface != NULL) {
> > > +        domain->interface->server_features = domain->features;
I just realized that the setting of interface->server_features needs
to be moved to introduce_domain(), as otherwise dom0 kernel won't see
the supported features.


Juergen

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