Patch "virtio_pci: fix virtio spec compliance on restore" has been added to the 3.14-stable tree

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This is a note to let you know that I've just added the patch titled

    virtio_pci: fix virtio spec compliance on restore

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     virtio_pci-fix-virtio-spec-compliance-on-restore.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 6fbc198cf623944ab60a1db6d306a4d55cdd820d Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Date: Tue, 14 Oct 2014 10:40:29 +1030
Subject: virtio_pci: fix virtio spec compliance on restore

From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

commit 6fbc198cf623944ab60a1db6d306a4d55cdd820d upstream.

On restore, virtio pci does the following:
+ set features
+ init vqs etc - device can be used at this point!
+ set ACKNOWLEDGE,DRIVER and DRIVER_OK status bits

This is in violation of the virtio spec, which
requires the following order:
- ACKNOWLEDGE
- DRIVER
- init vqs
- DRIVER_OK

This behaviour will break with hypervisors that assume spec compliant
behaviour.  It seems like a good idea to have this patch applied to
stable branches to reduce the support butden for the hypervisors.

Cc: Amit Shah <amit.shah@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/virtio/virtio_pci.c |   33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -791,6 +791,7 @@ static int virtio_pci_restore(struct dev
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
 	struct virtio_driver *drv;
+	unsigned status = 0;
 	int ret;
 
 	drv = container_of(vp_dev->vdev.dev.driver,
@@ -801,14 +802,40 @@ static int virtio_pci_restore(struct dev
 		return ret;
 
 	pci_set_master(pci_dev);
+	/* We always start by resetting the device, in case a previous
+	 * driver messed it up. */
+	vp_reset(&vp_dev->vdev);
+
+	/* Acknowledge that we've seen the device. */
+	status |= VIRTIO_CONFIG_S_ACKNOWLEDGE;
+	vp_set_status(&vp_dev->vdev, status);
+
+	/* Maybe driver failed before freeze.
+	 * Restore the failed status, for debugging. */
+	status |= vp_dev->saved_status & VIRTIO_CONFIG_S_FAILED;
+	vp_set_status(&vp_dev->vdev, status);
+
+	if (!drv)
+		return 0;
+
+	/* We have a driver! */
+	status |= VIRTIO_CONFIG_S_DRIVER;
+	vp_set_status(&vp_dev->vdev, status);
+
 	vp_finalize_features(&vp_dev->vdev);
 
-	if (drv && drv->restore)
+	if (drv->restore) {
 		ret = drv->restore(&vp_dev->vdev);
+		if (ret) {
+			status |= VIRTIO_CONFIG_S_FAILED;
+			vp_set_status(&vp_dev->vdev, status);
+			return ret;
+		}
+	}
 
 	/* Finally, tell the device we're all set */
-	if (!ret)
-		vp_set_status(&vp_dev->vdev, vp_dev->saved_status);
+	status |= VIRTIO_CONFIG_S_DRIVER_OK;
+	vp_set_status(&vp_dev->vdev, status);
 
 	return ret;
 }


Patches currently in stable-queue which might be from mst@xxxxxxxxxx are

queue-3.14/virtio_pci-fix-virtio-spec-compliance-on-restore.patch
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