[PATCH 5.12 089/127] xen-pciback: reconfigure also from backend watch handler

Greg Kroah-Hartman
2021-05-24T16:05:32Z

From: Jan Beulich <jbeulich@suse.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@suse.com>
Cc: stable@vger.kernel.org
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/2337cbd6-94b9-4187-9862-c03ea12e0c61@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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",
@@ -500,6 +499,10 @@ 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,
@@ -525,7 +528,7 @@ static void xen_pcibk_frontend_changed(s
break;

case XenbusStateReconfiguring:
- xen_pcibk_reconfigure(pdev);
+ xen_pcibk_reconfigure(pdev, XenbusStateReconfiguring);
break;

case XenbusStateConnected:
@@ -664,6 +667,15 @@ 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;
}