path: root/drivers/xen/xenbus
diff options
authorOlaf Hering <olaf@aepfle.de>2012-07-10 14:50:03 +0200
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2012-07-19 15:52:02 -0400
commit254d1a3f02ebc10ccc6e4903394d8d3f484f715e (patch)
tree3c3402e8d646173c1db00e3b78344ae515dc1af9 /drivers/xen/xenbus
parent1c32cdc633c96a14cca35de9db19338354c25111 (diff)
xen/pv-on-hvm kexec: shutdown watches from old kernel
Add xs_reset_watches function to shutdown watches from old kernel after kexec boot. The old kernel does not unregister all watches in the shutdown path. They are still active, the double registration can not be detected by the new kernel. When the watches fire, unexpected events will arrive and the xenwatch thread will crash (jumps to NULL). An orderly reboot of a hvm guest will destroy the entire guest with all its resources (including the watches) before it is rebuilt from scratch, so the missing unregister is not an issue in that case. With this change the xenstored is instructed to wipe all active watches for the guest. However, a patch for xenstored is required so that it accepts the XS_RESET_WATCHES request from a client (see changeset 23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored the registration of watches will fail and some features of a PVonHVM guest are not available. The guest is still able to boot, but repeated kexec boots will fail. Signed-off-by: Olaf Hering <olaf@aepfle.de> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/xen/xenbus')
1 files changed, 20 insertions, 0 deletions
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index d1c217b23a4..bce15cf4a8d 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -618,6 +618,23 @@ static struct xenbus_watch *find_watch(const char *token)
return NULL;
+static void xs_reset_watches(void)
+ int err, supported = 0;
+ if (!xen_hvm_domain())
+ return;
+ err = xenbus_scanf(XBT_NIL, "control",
+ "platform-feature-xs_reset_watches", "%d", &supported);
+ if (err != 1 || !supported)
+ return;
+ err = xs_error(xs_single(XBT_NIL, XS_RESET_WATCHES, "", NULL));
+ if (err && err != -EEXIST)
+ printk(KERN_WARNING "xs_reset_watches failed: %d\n", err);
/* Register callback to watch this node. */
int register_xenbus_watch(struct xenbus_watch *watch)
@@ -900,5 +917,8 @@ int xs_init(void)
if (IS_ERR(task))
return PTR_ERR(task);
+ /* shutdown watches for kexec boot */
+ xs_reset_watches();
return 0;