From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755184Ab1HDQVt (ORCPT ); Thu, 4 Aug 2011 12:21:49 -0400 Received: from mo-p00-ob.rzone.de ([81.169.146.160]:8363 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754126Ab1HDQVo (ORCPT ); Thu, 4 Aug 2011 12:21:44 -0400 X-RZG-AUTH: :P2EQZWCpfu+qG7CngxMFH1J+zrwiavkK6tmQaLfmwtM48/ll2c7pEOUO X-RZG-CLASS-ID: mo00 Message-Id: <20110804162054.806626433@aepfle.de> User-Agent: quilt/0.48-16.4 Date: Thu, 04 Aug 2011 18:20:56 +0200 From: Olaf Hering To: linux-kernel@vger.kernel.org, Jeremy Fitzhardinge , Konrad Cc: xen-devel@lists.xensource.com Subject: [PATCH 3/3] xen/pv-on-hvm kexec+kdump: reset PV devices in kexec or crash kernel References: <20110804162053.723541930@aepfle.de> Content-Disposition: inline; filename=xen.kexec-kdump.reconnect-devices.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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);