[xen master] tools/xenstore: handle dying domains in live update

[patchbot@xxxxxxx]

commit 939775cfd3ad6bce5aa350b7f60e0eb48914257f
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Wed Jan 13 14:00:21 2021 +0100
Commit:     Juergen Gross <jgross@xxxxxxxx>
CommitDate: Thu Jan 21 17:31:52 2021 +0100

    tools/xenstore: handle dying domains in live update
    
    A domain could just be dying when live updating Xenstore, so the case
    of not being able to map the ring page or to connect to the event
    channel must be handled gracefully.
    
    Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
    Acked-by: Wei Liu <wl@xxxxxxx>
---
 tools/xenstore/xenstored_control.c |  7 +++++++
 tools/xenstore/xenstored_domain.c  | 25 +++++++++++++++++--------
 tools/xenstore/xenstored_domain.h  |  2 ++
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/tools/xenstore/xenstored_control.c 
b/tools/xenstore/xenstored_control.c
index b8195eed41..3c212cc4d4 100644
--- a/tools/xenstore/xenstored_control.c
+++ b/tools/xenstore/xenstored_control.c
@@ -561,6 +561,13 @@ void lu_read_state(void)
        lu_close_dump_state(&state);
 
        talloc_free(ctx);
+
+       /*
+        * We may have missed the VIRQ_DOM_EXC notification and a domain may
+        * have died while we were live-updating. So check all the domains are
+        * still alive.
+        */
+       check_domains(true);
 }
 
 static const char *lu_activate_binary(const void *ctx)
diff --git a/tools/xenstore/xenstored_domain.c 
b/tools/xenstore/xenstored_domain.c
index 6934f1bc89..cbeb2a309c 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -220,7 +220,7 @@ static bool get_domain_info(unsigned int domid, 
xc_dominfo_t *dominfo)
               dominfo->domid == domid;
 }
 
-static void domain_cleanup(void)
+void check_domains(bool restore)
 {
        xc_dominfo_t dominfo;
        struct domain *domain;
@@ -244,7 +244,14 @@ static void domain_cleanup(void)
                                domain->shutdown = true;
                                notify = 1;
                        }
-                       if (!dominfo.dying)
+                       /*
+                        * On Restore, we may have been unable to remap the
+                        * interface and the port. As we don't know whether
+                        * this was because of a dying domain, we need to
+                        * check if the interface and port are still valid.
+                        */
+                       if (!dominfo.dying && domain->port &&
+                           domain->interface)
                                continue;
                }
                if (domain->conn) {
@@ -270,7 +277,7 @@ void handle_event(void)
                barf_perror("Failed to read from event fd");
 
        if (port == virq_port)
-               domain_cleanup();
+               check_domains(false);
 
        if (xenevtchn_unmask(xce_handle, port) == -1)
                barf_perror("Failed to write to event fd");
@@ -442,14 +449,16 @@ static struct domain *introduce_domain(const void *ctx,
        if (!domain->introduced) {
                interface = is_master_domain ? xenbus_map()
                                             : map_interface(domid);
-               if (!interface)
+               if (!interface && !restore)
                        return NULL;
                if (new_domain(domain, port, restore)) {
                        rc = errno;
-                       if (is_master_domain)
-                               unmap_xenbus(interface);
-                       else
-                               unmap_interface(interface);
+                       if (interface) {
+                               if (is_master_domain)
+                                       unmap_xenbus(interface);
+                               else
+                                       unmap_interface(interface);
+                       }
                        errno = rc;
                        return NULL;
                }
diff --git a/tools/xenstore/xenstored_domain.h 
b/tools/xenstore/xenstored_domain.h
index 8f3b4e0f8b..1cc1c03ed8 100644
--- a/tools/xenstore/xenstored_domain.h
+++ b/tools/xenstore/xenstored_domain.h
@@ -21,6 +21,8 @@
 
 void handle_event(void);
 
+void check_domains(bool restore);
+
 /* domid, mfn, eventchn, path */
 int do_introduce(struct connection *conn, struct buffered_data *in);
 
--
generated by git-patchbot for /home/xen/git/xen.git#master