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xen-pciback: reconfigure also from backend watch handler
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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>
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Jan Beulich authored and Juergen Gross committed May 21, 2021
1 parent 4ba50e7 commit c81d3d2
Showing 1 changed file with 17 additions and 5 deletions.
22 changes: 17 additions & 5 deletions drivers/xen/xen-pciback/xenbus.c
Original file line number Diff line number Diff line change
@@ -359,7 +359,8 @@ static int xen_pcibk_publish_pci_root(struct xen_pcibk_device *pdev,
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 xen_pcibk_device *pdev)
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 xen_pcibk_device *pdev)
}
}

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(struct xenbus_device *xdev,
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 xenbus_watch *watch,
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;
}

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