WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] [PATCH 3/3] xen/pv-on-hvm kexec+kdump: reset PV devices in k

To: linux-kernel@xxxxxxxxxxxxxxx, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Konrad <konrad.wilk@xxxxxxxxxx>
Subject: [Xen-devel] [PATCH 3/3] xen/pv-on-hvm kexec+kdump: reset PV devices in kexec or crash kernel
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Thu, 04 Aug 2011 18:20:56 +0200
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Thu, 04 Aug 2011 09:22:39 -0700
Dkim-signature: v=1; a=rsa-sha1; c=relaxed/relaxed; t=1312474908; l=5353; s=domk; d=aepfle.de; h=References:Subject:Cc:To:From:Date:X-RZG-CLASS-ID:X-RZG-AUTH; bh=aMxc4qQnDSWgZ+7hjFXf42+Z22I=; b=x9k08AGgG6STcnb5ox3AfgP1ajnK/I/dl7MTjJ/jNjmvtenlUM/xiYClc/d5bsxwoWn 6S3Nv3Up2ueX08cU55zeokq8J8U9eetPEquaBGpxOn0PZf2YagYXyQlPKcgBEfMNpgx9/ eoKZERBNxWjfG/OC7K7ChpB/lVQ2n04LyLk=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <20110804162053.723541930@xxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: quilt/0.48-16.4
After triggering a crash dump in a HVM guest, the PV backend drivers
will remain in Connected state. When the kdump kernel starts the PV
drivers will skip such devices. As a result, no root device is found and
the vmcore cant be saved.  

A similar situation happens after a kexec boot, here the devices will be
in the Closed state.

With this change all frontend devices with state XenbusStateConnected or
XenbusStateClosed will be reset by changing the state file to
Closing/Closed/Initializing.  This will trigger a disconnect in the
backend drivers. Now the frontend drivers will find the backend drivers
in state Initwait and can connect.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

---
 drivers/xen/xenbus/xenbus_comms.c          |    4 -
 drivers/xen/xenbus/xenbus_probe_frontend.c |  116 +++++++++++++++++++++++++++++
 2 files changed, 119 insertions(+), 1 deletion(-)

Index: linux-3.0/drivers/xen/xenbus/xenbus_comms.c
===================================================================
--- linux-3.0.orig/drivers/xen/xenbus/xenbus_comms.c
+++ linux-3.0/drivers/xen/xenbus/xenbus_comms.c
@@ -212,7 +212,9 @@ int xb_init_comms(void)
                printk(KERN_WARNING "XENBUS response ring is not quiescent "
                       "(%08x:%08x): fixing up\n",
                       intf->rsp_cons, intf->rsp_prod);
-               intf->rsp_cons = intf->rsp_prod;
+               /* breaks kdump */
+               if (!reset_devices)
+                       intf->rsp_cons = intf->rsp_prod;
        }
 
        if (xenbus_irq) {
Index: linux-3.0/drivers/xen/xenbus/xenbus_probe_frontend.c
===================================================================
--- linux-3.0.orig/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ linux-3.0/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -252,10 +252,126 @@ int __xenbus_register_frontend(struct xe
 }
 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
 
+static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
+static int backend_state;
+
+static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
+                                       const char **v, unsigned int l)
+{
+       xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
+       printk(KERN_DEBUG "XENBUS: %s %s\n",
+                       v[XS_WATCH_PATH], xenbus_strstate(backend_state));
+       wake_up(&backend_state_wq);
+}
+
+static void xenbus_reset_wait_for_backend(int expected)
+{
+       wait_event_interruptible(backend_state_wq, backend_state == expected);
+}
+
+/*
+ * Reset frontend if it is in Connected or Closed state.
+ * Wait for backend to catch up.
+ * State Connected happens during kdump, Closed after kexec.
+ */
+static void xenbus_reset_frontend(char *fe, char *be, int be_state)
+{
+       struct xenbus_watch be_watch;
+
+       printk(KERN_DEBUG "XENBUS: backend %s %s\n",
+                       be, xenbus_strstate(be_state));
+
+       memset(&be_watch, 0, sizeof(be_watch));
+       be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
+       if (!be_watch.node)
+               return;
+
+       be_watch.callback = xenbus_reset_backend_state_changed;
+       backend_state = XenbusStateUnknown;
+
+       printk(KERN_INFO "XENBUS: triggering reconnect on %s\n", be);
+       register_xenbus_watch(&be_watch);
+
+       switch (be_state) {
+       case XenbusStateConnected:
+               xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
+               xenbus_reset_wait_for_backend(XenbusStateClosing);
+
+       case XenbusStateClosing:
+               xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
+               xenbus_reset_wait_for_backend(XenbusStateClosed);
+
+       case XenbusStateClosed:
+               xenbus_printf(XBT_NIL, fe, "state", "%d", 
XenbusStateInitialising);
+               xenbus_reset_wait_for_backend(XenbusStateInitWait);
+       }
+
+       unregister_xenbus_watch(&be_watch);
+       printk(KERN_INFO "XENBUS: reconnect done on %s\n", be);
+       kfree(be_watch.node);
+}
+
+static void xenbus_check_frontend(char *class, char *dev)
+{
+       int be_state, fe_state, err;
+       char *backend, *frontend;
+
+       frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
+       if (!frontend)
+               return;
+
+       err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
+       if (err != 1)
+               goto out;
+
+       switch (fe_state) {
+       case XenbusStateConnected:
+       case XenbusStateClosed:
+               printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
+                               frontend, xenbus_strstate(fe_state));
+               backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
+               if (!backend || IS_ERR(backend))
+                       goto out;
+               err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
+               if (err == 1)
+                       xenbus_reset_frontend(frontend, backend, be_state);
+               kfree(backend);
+               break;
+       default:
+               break;
+       }
+out:
+       kfree(frontend);
+}
+
+static void xenbus_reset_state(void)
+{
+       char **devclass, **dev;
+       int devclass_n, dev_n;
+       int i, j;
+
+       devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
+       if (IS_ERR(devclass))
+               return;
+
+       for (i = 0; i < devclass_n; i++) {
+               dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
+               if (IS_ERR(dev))
+                       continue;
+               for (j = 0; j < dev_n; j++)
+                       xenbus_check_frontend(devclass[i], dev[j]);
+               kfree(dev);
+       }
+       kfree(devclass);
+}
+
 static int frontend_probe_and_watch(struct notifier_block *notifier,
                                   unsigned long event,
                                   void *data)
 {
+       /* reset devices in Connected or Closed state */
+       if (xen_hvm_domain())
+               xenbus_reset_state();
        /* Enumerate devices in xenstore and watch for changes. */
        xenbus_probe_devices(&xenbus_frontend);
        register_xenbus_watch(&fe_watch);


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>