[PATCH 3.16.y-ckt 093/129] xen/xenbus: Update xenbus event channel on resume

[Luis Henriques]

3.16.7-ckt12 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

commit 16f1cf3ba7303228372d3756677bf7d10e79cf9f upstream.

After a resume the hypervisor/tools may change xenbus event
channel number. We should re-query it.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/xen/xenbus/xenbus_probe.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 3c0a74b3e9b1..7d6de403e450 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -57,6 +57,7 @@
 #include <xen/xen.h>
 #include <xen/xenbus.h>
 #include <xen/events.h>
+#include <xen/xen-ops.h>
 #include <xen/page.h>
 
 #include <xen/hvm.h>
@@ -731,6 +732,30 @@ static int __init xenstored_local_init(void)
 	return err;
 }
 
+static int xenbus_resume_cb(struct notifier_block *nb,
+			    unsigned long action, void *data)
+{
+	int err = 0;
+
+	if (xen_hvm_domain()) {
+		uint64_t v;
+
+		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
+		if (!err && v)
+			xen_store_evtchn = v;
+		else
+			pr_warn("Cannot update xenstore event channel: %d\n",
+				err);
+	} else
+		xen_store_evtchn = xen_start_info->store_evtchn;
+
+	return err;
+}
+
+static struct notifier_block xenbus_resume_nb = {
+	.notifier_call = xenbus_resume_cb,
+};
+
 static int __init xenbus_init(void)
 {
 	int err = 0;
@@ -789,6 +814,10 @@ static int __init xenbus_init(void)
 		goto out_error;
 	}
 
+	if ((xen_store_domain_type != XS_LOCAL) &&
+	    (xen_store_domain_type != XS_UNKNOWN))
+		xen_resume_notifier_register(&xenbus_resume_nb);
+
 #ifdef CONFIG_XEN_COMPAT_XENFS
 	/*
 	 * Create xenfs mountpoint in /proc for compatibility with
--
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