From: Bill Burns <bburns@redhat.com>
Date: Mon, 26 Jan 2009 11:53:55 -0500
Subject: [xen] fix disappearing PCI devices from PV guests
Message-id: 497DEAA3.1030507@redhat.com
O-Subject: Re: [RHEL5.4 PATCH v2] Fix disappearing PCI devices from Xen PV guests
Bugzilla: 233801
RH-Acked-by: Markus Armbruster <armbru@redhat.com>
RH-Acked-by: Rik van Riel <riel@redhat.com>
RH-Acked-by: Chris Lalancette <clalance@redhat.com>
RH-Acked-by: Markus Armbruster <armbru@redhat.com>

Version 2, simple whitespace fix.

Bill Burns wrote:
> Fixes bz 233801
>
> Problem description:
>
> PCI devices passed through to Xen PV guests can disappear
> on reboot. This worked on some configurations and was thought
> to be a race. But incorrect operations in the Xenstore were the
> reason for the condition. Jiri Denemark troubleshot this from
> the used mode perspective and initially thought that it was both
> a kernel and user space issue. Then he found that it was
> actually a just kernel issue and proved it with a simple
> patch. We found the same change upstream and this patch
> is a slight re-work of that. The only re-work was to deal
> with adjacent code that changed, so the patch is logically
> identical.
>
> Upstream status:
>
> http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/5644f68a7912
>
> Brew build:
>
> https://brewweb.devel.redhat.com/taskinfo?taskID=1644512

>
> Testing:
>
> Jirka tested with the brew build and verified proper
> operation.
>
> Please review and ACK.
>
> Thanks,
>  Bill
>

changeset: pcifront/back: Fix handling of device disconnect.
changeset 604: 	5644f68a7912
parent 603:	bd4b58143713
child 605:	2d2436c48e43
author: 	Keir Fraser <keir.fraser@citrix.com>
date: 	Wed Jul 16 13:51:36 2008 +0100 (6 months ago)
files: 	drivers/xen/pciback/xenbus.c drivers/xen/pcifront/xenbus.c
description: 	pcifront/back: Fix handling of device disconnect.

Signed-off-by: Yosuke Iwamatsu <y-iwamatsu@ab.jp.nec.com>

diff --git a/drivers/xen/pciback/xenbus.c b/drivers/xen/pciback/xenbus.c
index 0026753..e2a7d1d 100644
--- a/drivers/xen/pciback/xenbus.c
+++ b/drivers/xen/pciback/xenbus.c
@@ -42,22 +42,35 @@ static struct pciback_device *alloc_pdev(struct xenbus_device *xdev)
 	return pdev;
 }
 
-static void free_pdev(struct pciback_device *pdev)
+static void pciback_disconnect(struct pciback_device *pdev)
 {
-	if (pdev->be_watching)
-		unregister_xenbus_watch(&pdev->be_watch);
+	spin_lock(&pdev->dev_lock);
 
 	/* Ensure the guest can't trigger our handler before removing devices */
-	if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ)
+	if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ) {
 		unbind_from_irqhandler(pdev->evtchn_irq, pdev);
+		pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
+	}
 
 	/* If the driver domain started an op, make sure we complete it or
 	 * delete it before releasing the shared memory */
 	cancel_delayed_work(&pdev->op_work);
 	flush_scheduled_work();
 
-	if (pdev->sh_info)
+	if (pdev->sh_info != NULL) {
 		xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_area);
+		pdev->sh_info = NULL;
+	}
+
+	spin_unlock(&pdev->dev_lock);
+}
+
+static void free_pdev(struct pciback_device *pdev)
+{
+	if (pdev->be_watching)
+		unregister_xenbus_watch(&pdev->be_watch);
+
+	pciback_disconnect(pdev);
 
 	pciback_release_devices(pdev);
 
@@ -178,11 +191,17 @@ static void pciback_frontend_changed(struct xenbus_device *xdev,
 		break;
 
 	case XenbusStateClosing:
+		pciback_disconnect(pdev);
 		xenbus_switch_state(xdev, XenbusStateClosing);
 		break;
 
-	case XenbusStateUnknown:
 	case XenbusStateClosed:
+		pciback_disconnect(pdev);
+		xenbus_switch_state(xdev, XenbusStateClosed);
+		if (xenbus_dev_is_online(xdev))
+			break;
+		/* fall through if not online */
+	case XenbusStateUnknown:
 		dev_dbg(&xdev->dev, "frontend is gone! unregister device\n");
 		device_unregister(&xdev->dev);
 		break;
diff --git a/drivers/xen/pcifront/xenbus.c b/drivers/xen/pcifront/xenbus.c
index 6231c81..bda7df5 100644
--- a/drivers/xen/pcifront/xenbus.c
+++ b/drivers/xen/pcifront/xenbus.c
@@ -203,12 +203,17 @@ static int pcifront_try_disconnect(struct pcifront_device *pdev)
 
 	prev_state = xenbus_read_driver_state(pdev->xdev->nodename);
 
-	if (prev_state < XenbusStateClosing)
-		err = xenbus_switch_state(pdev->xdev, XenbusStateClosing);
+	if (prev_state >= XenbusStateClosing)
+		goto out;
 
-	if (!err && prev_state == XenbusStateConnected)
+	if(prev_state == XenbusStateConnected) {
+		pcifront_free_roots(pdev);
 		pcifront_disconnect(pdev);
+	}
+
+	err = xenbus_switch_state(pdev->xdev, XenbusStateClosed);
 
+      out:
 	spin_unlock(&pdev->dev_lock);
 
 	return err;
@@ -220,24 +225,20 @@ static void pcifront_backend_changed(struct xenbus_device *xdev,
 	struct pcifront_device *pdev = xdev->dev.driver_data;
 
 	switch (be_state) {
-	case XenbusStateClosing:
-		dev_warn(&xdev->dev, "backend going away!\n");
-		pcifront_try_disconnect(pdev);
-		break;
-
 	case XenbusStateUnknown:
+	case XenbusStateInitialising:
+	case XenbusStateInitWait:
+	case XenbusStateInitialised:
 	case XenbusStateClosed:
-		dev_warn(&xdev->dev, "backend went away!\n");
-		pcifront_try_disconnect(pdev);
-
-		device_unregister(&pdev->xdev->dev);
 		break;
 
 	case XenbusStateConnected:
 		pcifront_try_connect(pdev);
 		break;
 
-	default:
+ 	case XenbusStateClosing:
+		dev_warn(&xdev->dev, "backend going away!\n");
+		pcifront_try_disconnect(pdev);
 		break;
 	}
 }