From 254d1a3f02ebc10ccc6e4903394d8d3f484f715e Mon Sep 17 00:00:00 2001 From: Olaf Hering Date: Tue, 10 Jul 2012 14:50:03 +0200 Subject: [PATCH] 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 Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/xenbus/xenbus_xs.c | 20 ++++++++++++++++++++ include/xen/interface/io/xs_wire.h | 3 ++- 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c index d1c217b23a42..bce15cf4a8df 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; } diff --git a/include/xen/interface/io/xs_wire.h b/include/xen/interface/io/xs_wire.h index 7cdfca24eafb..794deb07eb53 100644 --- a/include/xen/interface/io/xs_wire.h +++ b/include/xen/interface/io/xs_wire.h @@ -29,7 +29,8 @@ enum xsd_sockmsg_type XS_IS_DOMAIN_INTRODUCED, XS_RESUME, XS_SET_TARGET, - XS_RESTRICT + XS_RESTRICT, + XS_RESET_WATCHES, }; #define XS_WRITE_NONE "NONE" -- 2.20.1