linux-kernel - [PATCH 4.4 08/31] xen-pciback: reconfigure also from backend watch handler

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Date:   Mon, 24 May 2021 17:24:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jan Beulich <jbeulich@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>
Subject: [PATCH 4.4 08/31] xen-pciback: reconfigure also from backend watch handler

From: Jan Beulich <jbeulich@...e.com>

commit c81d3d24602540f65256f98831d0a25599ea6b87 upstream.

When multiple PCI devices get assigned to a guest right at boot, libxl
incrementally populates the backend tree. The writes for the first of
the devices trigger the backend watch. In turn xen_pcibk_setup_backend()
will set the XenBus state to Initialised, at which point no further
reconfigures would happen unless a device got hotplugged. Arrange for
reconfigure to also get triggered from the backend watch handler.

Signed-off-by: Jan Beulich <jbeulich@...e.com>
Cc: stable@...r.kernel.org
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Link: https://lore.kernel.org/r/2337cbd6-94b9-4187-9862-c03ea12e0c61@suse.com
Signed-off-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/xen/xen-pciback/xenbus.c |   22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -359,7 +359,8 @@ out:
 	return err;
 }
 
-static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev)
+static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev,
+				 enum xenbus_state state)
 {
 	int err = 0;
 	int num_devs;
@@ -373,9 +374,7 @@ static int xen_pcibk_reconfigure(struct
 	dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n");
 
 	mutex_lock(&pdev->dev_lock);
-	/* Make sure we only reconfigure once */
-	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
-	    XenbusStateReconfiguring)
+	if (xenbus_read_driver_state(pdev->xdev->nodename) != state)
 		goto out;
 
 	err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
@@ -502,6 +501,10 @@ static int xen_pcibk_reconfigure(struct
 		}
 	}
 
+	if (state != XenbusStateReconfiguring)
+		/* Make sure we only reconfigure once. */
+		goto out;
+
 	err = xenbus_switch_state(pdev->xdev, XenbusStateReconfigured);
 	if (err) {
 		xenbus_dev_fatal(pdev->xdev, err,
@@ -527,7 +530,7 @@ static void xen_pcibk_frontend_changed(s
 		break;
 
 	case XenbusStateReconfiguring:
-		xen_pcibk_reconfigure(pdev);
+		xen_pcibk_reconfigure(pdev, XenbusStateReconfiguring);
 		break;
 
 	case XenbusStateConnected:
@@ -666,6 +669,15 @@ static void xen_pcibk_be_watch(struct xe
 		xen_pcibk_setup_backend(pdev);
 		break;
 
+	case XenbusStateInitialised:
+		/*
+		 * We typically move to Initialised when the first device was
+		 * added. Hence subsequent devices getting added may need
+		 * reconfiguring.
+		 */
+		xen_pcibk_reconfigure(pdev, XenbusStateInitialised);
+		break;
+
 	default:
 		break;
 	}