[PATCH 0/2] xen/xenbus: better handle backend crash

[PATCH 0/2] xen/xenbus: better handle backend crash

[Juergen Gross]

This small series fixes PV-device frontend side handling in case the
backend crashed and has come up again.

The old device will be discarded and the replacement can be used
instead. 

Juergen Gross (2):
  xenbus: add xenbus_device parameter to xenbus_read_driver_state()
  xen/xenbus: better handle backend crash

 drivers/net/xen-netfront.c                 | 34 +++++++++---------
 drivers/pci/xen-pcifront.c                 |  8 ++---
 drivers/scsi/xen-scsifront.c               |  2 +-
 drivers/xen/xen-pciback/xenbus.c           | 10 +++---
 drivers/xen/xenbus/xenbus_client.c         | 16 +++++++--
 drivers/xen/xenbus/xenbus_probe.c          | 42 ++++++++++++++++++++--
 drivers/xen/xenbus/xenbus_probe_frontend.c |  2 +-
 include/xen/xenbus.h                       |  4 ++-
 8 files changed, 83 insertions(+), 35 deletions(-)

-- 
2.53.0

[PATCH 1/2] xenbus: add xenbus_device parameter to xenbus_read_driver_state()

[Juergen Gross]

In order to prepare checking the xenbus device status in
xenbus_read_driver_state(), add the pointer to struct xenbus_device
as a parameter.

Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 drivers/net/xen-netfront.c                 | 34 +++++++++++-----------
 drivers/pci/xen-pcifront.c                 |  8 ++---
 drivers/scsi/xen-scsifront.c               |  2 +-
 drivers/xen/xen-pciback/xenbus.c           | 10 +++----
 drivers/xen/xenbus/xenbus_client.c         |  3 +-
 drivers/xen/xenbus/xenbus_probe.c          |  6 ++--
 drivers/xen/xenbus/xenbus_probe_frontend.c |  2 +-
 include/xen/xenbus.h                       |  3 +-
 8 files changed, 35 insertions(+), 33 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 0969d5c9f6b7..2c414b77dd0f 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1646,7 +1646,7 @@ static int xennet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 
 	/* avoid the race with XDP headroom adjustment */
 	wait_event(module_wq,
-		   xenbus_read_driver_state(np->xbdev->otherend) ==
+		   xenbus_read_driver_state(np->xbdev, np->xbdev->otherend) ==
 		   XenbusStateReconfigured);
 	np->netfront_xdp_enabled = true;
 
@@ -1764,9 +1764,9 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
 	do {
 		xenbus_switch_state(dev, XenbusStateInitialising);
 		err = wait_event_timeout(module_wq,
-				 xenbus_read_driver_state(dev->otherend) !=
+				 xenbus_read_driver_state(dev, dev->otherend) !=
 				 XenbusStateClosed &&
-				 xenbus_read_driver_state(dev->otherend) !=
+				 xenbus_read_driver_state(dev, dev->otherend) !=
 				 XenbusStateUnknown, XENNET_TIMEOUT);
 	} while (!err);
 
@@ -2627,31 +2627,31 @@ static void xennet_bus_close(struct xenbus_device *dev)
 {
 	int ret;
 
-	if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+	if (xenbus_read_driver_state(dev, dev->otherend) == XenbusStateClosed)
 		return;
 	do {
 		xenbus_switch_state(dev, XenbusStateClosing);
 		ret = wait_event_timeout(module_wq,
-				   xenbus_read_driver_state(dev->otherend) ==
-				   XenbusStateClosing ||
-				   xenbus_read_driver_state(dev->otherend) ==
-				   XenbusStateClosed ||
-				   xenbus_read_driver_state(dev->otherend) ==
-				   XenbusStateUnknown,
-				   XENNET_TIMEOUT);
+				xenbus_read_driver_state(dev, dev->otherend) ==
+				XenbusStateClosing ||
+				xenbus_read_driver_state(dev, dev->otherend) ==
+				XenbusStateClosed ||
+				xenbus_read_driver_state(dev, dev->otherend) ==
+				XenbusStateUnknown,
+				XENNET_TIMEOUT);
 	} while (!ret);
 
-	if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+	if (xenbus_read_driver_state(dev, dev->otherend) == XenbusStateClosed)
 		return;
 
 	do {
 		xenbus_switch_state(dev, XenbusStateClosed);
 		ret = wait_event_timeout(module_wq,
-				   xenbus_read_driver_state(dev->otherend) ==
-				   XenbusStateClosed ||
-				   xenbus_read_driver_state(dev->otherend) ==
-				   XenbusStateUnknown,
-				   XENNET_TIMEOUT);
+				xenbus_read_driver_state(dev, dev->otherend) ==
+				XenbusStateClosed ||
+				xenbus_read_driver_state(dev, dev->otherend) ==
+				XenbusStateUnknown,
+				XENNET_TIMEOUT);
 	} while (!ret);
 }
 
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index 11636634ae51..cd22bf984024 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -856,7 +856,7 @@ static void pcifront_try_connect(struct pcifront_device *pdev)
 	int err;
 
 	/* Only connect once */
-	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) !=
 	    XenbusStateInitialised)
 		return;
 
@@ -876,7 +876,7 @@ static int pcifront_try_disconnect(struct pcifront_device *pdev)
 	enum xenbus_state prev_state;
 
 
-	prev_state = xenbus_read_driver_state(pdev->xdev->nodename);
+	prev_state = xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename);
 
 	if (prev_state >= XenbusStateClosing)
 		goto out;
@@ -895,7 +895,7 @@ static int pcifront_try_disconnect(struct pcifront_device *pdev)
 
 static void pcifront_attach_devices(struct pcifront_device *pdev)
 {
-	if (xenbus_read_driver_state(pdev->xdev->nodename) ==
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) ==
 	    XenbusStateReconfiguring)
 		pcifront_connect(pdev);
 }
@@ -909,7 +909,7 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
 	struct pci_dev *pci_dev;
 	char str[64];
 
-	state = xenbus_read_driver_state(pdev->xdev->nodename);
+	state = xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename);
 	if (state == XenbusStateInitialised) {
 		dev_dbg(&pdev->xdev->dev, "Handle skipped connect.\n");
 		/* We missed Connected and need to initialize. */
diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
index 924025305753..ef74d4da5ab0 100644
--- a/drivers/scsi/xen-scsifront.c
+++ b/drivers/scsi/xen-scsifront.c
@@ -1175,7 +1175,7 @@ static void scsifront_backend_changed(struct xenbus_device *dev,
 			return;
 		}
 
-		if (xenbus_read_driver_state(dev->nodename) ==
+		if (xenbus_read_driver_state(dev, dev->nodename) ==
 		    XenbusStateInitialised)
 			scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
 
diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index b11e401f1b1e..4bd1c7a8957e 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -149,12 +149,12 @@ static int xen_pcibk_attach(struct xen_pcibk_device *pdev)
 
 	mutex_lock(&pdev->dev_lock);
 	/* Make sure we only do this setup once */
-	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) !=
 	    XenbusStateInitialised)
 		goto out;
 
 	/* Wait for frontend to state that it has published the configuration */
-	if (xenbus_read_driver_state(pdev->xdev->otherend) !=
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->otherend) !=
 	    XenbusStateInitialised)
 		goto out;
 
@@ -374,7 +374,7 @@ static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev,
 	dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n");
 
 	mutex_lock(&pdev->dev_lock);
-	if (xenbus_read_driver_state(pdev->xdev->nodename) != state)
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) != state)
 		goto out;
 
 	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
@@ -572,7 +572,7 @@ static int xen_pcibk_setup_backend(struct xen_pcibk_device *pdev)
 	/* It's possible we could get the call to setup twice, so make sure
 	 * we're not already connected.
 	 */
-	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) !=
 	    XenbusStateInitWait)
 		goto out;
 
@@ -662,7 +662,7 @@ static void xen_pcibk_be_watch(struct xenbus_watch *watch,
 	struct xen_pcibk_device *pdev =
 	    container_of(watch, struct xen_pcibk_device, be_watch);
 
-	switch (xenbus_read_driver_state(pdev->xdev->nodename)) {
+	switch (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename)) {
 	case XenbusStateInitWait:
 		xen_pcibk_setup_backend(pdev);
 		break;
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 2dc874fb5506..6ed0cd8e9676 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -936,7 +936,8 @@ static int xenbus_unmap_ring_hvm(struct xenbus_device *dev, void *vaddr)
  * Returns: the state of the driver rooted at the given store path, or
  * XenbusStateUnknown if no state can be read.
  */
-enum xenbus_state xenbus_read_driver_state(const char *path)
+enum xenbus_state xenbus_read_driver_state(const struct xenbus_device *dev,
+					   const char *path)
 {
 	enum xenbus_state result;
 	int err = xenbus_gather(XBT_NIL, path, "state", "%d", &result, NULL);
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 9f9011cd7447..2eed06ba5d38 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -191,7 +191,7 @@ void xenbus_otherend_changed(struct xenbus_watch *watch,
 		return;
 	}
 
-	state = xenbus_read_driver_state(dev->otherend);
+	state = xenbus_read_driver_state(dev, dev->otherend);
 
 	dev_dbg(&dev->dev, "state is %d, (%s), %s, %s\n",
 		state, xenbus_strstate(state), dev->otherend_watch.node, path);
@@ -364,7 +364,7 @@ void xenbus_dev_remove(struct device *_dev)
 	 * closed.
 	 */
 	if (!drv->allow_rebind ||
-	    xenbus_read_driver_state(dev->nodename) == XenbusStateClosing)
+	    xenbus_read_driver_state(dev, dev->nodename) == XenbusStateClosing)
 		xenbus_switch_state(dev, XenbusStateClosed);
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_remove);
@@ -514,7 +514,7 @@ int xenbus_probe_node(struct xen_bus_type *bus,
 	size_t stringlen;
 	char *tmpstring;
 
-	enum xenbus_state state = xenbus_read_driver_state(nodename);
+	enum xenbus_state state = xenbus_read_driver_state(NULL, nodename);
 
 	if (state != XenbusStateInitialising) {
 		/* Device is not new, so ignore it.  This can happen if a
diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
index f04707d1f667..ca04609730df 100644
--- a/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -253,7 +253,7 @@ static int print_device_status(struct device *dev, void *data)
 	} else if (xendev->state < XenbusStateConnected) {
 		enum xenbus_state rstate = XenbusStateUnknown;
 		if (xendev->otherend)
-			rstate = xenbus_read_driver_state(xendev->otherend);
+			rstate = xenbus_read_driver_state(xendev, xendev->otherend);
 		pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
 			xendev->nodename, xendev->state, rstate);
 	}
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index c94caf852aea..15319da65b7f 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -228,7 +228,8 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr);
 int xenbus_alloc_evtchn(struct xenbus_device *dev, evtchn_port_t *port);
 int xenbus_free_evtchn(struct xenbus_device *dev, evtchn_port_t port);
 
-enum xenbus_state xenbus_read_driver_state(const char *path);
+enum xenbus_state xenbus_read_driver_state(const struct xenbus_device *dev,
+					   const char *path);
 
 __printf(3, 4)
 void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...);
-- 
2.53.0

Re: [PATCH 1/2] xenbus: add xenbus_device parameter to xenbus_read_driver_state()

[kernel test robot]

Hi Juergen,

kernel test robot noticed the following build warnings:

[auto build test WARNING on xen-tip/linux-next]
[also build test WARNING on linus/master v6.19 next-20260211]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Juergen-Gross/xenbus-add-xenbus_device-parameter-to-xenbus_read_driver_state/20260212-164134
base:   https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git linux-next
patch link:    https://lore.kernel.org/r/20260212083826.136221-2-jgross%40suse.com
patch subject: [PATCH 1/2] xenbus: add xenbus_device parameter to xenbus_read_driver_state()
config: x86_64-rhel-9.4-ltp (https://download.01.org/0day-ci/archive/20260212/202602121525.xsMivuEv-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260212/202602121525.xsMivuEv-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602121525.xsMivuEv-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: drivers/xen/xenbus/xenbus_client.c:940 function parameter 'dev' not described in 'xenbus_read_driver_state'
>> Warning: drivers/xen/xenbus/xenbus_client.c:940 function parameter 'dev' not described in 'xenbus_read_driver_state'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki