Patch "virtio: virtio 1.0 cs04 spec compliance for reset" has been added to the 4.4-stable tree

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

virtio: virtio 1.0 cs04 spec compliance for reset

to the 4.4-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-virtio-1.0-cs04-spec-compliance-for-reset.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Michael S. Tsirkin" <[email protected]>
Date: Sun, 3 Apr 2016 15:23:37 +0300
Subject: virtio: virtio 1.0 cs04 spec compliance for reset

From: Michael S. Tsirkin <[email protected]>

commit 05dbcb430795b2e1fb1d5c757f8619d3dbed0a1c upstream.

The spec says: after writing 0 to device_status, the driver MUST wait for a read of device_status to return 0 before reinitializing the device.

---
 drivers/virtio/virtio_pci_modern.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

@@ -17,6 +17,7 @@
  *
  */
 
+#include <linux/delay.h>
 #define VIRTIO_PCI_NO_LEGACY
 #include "virtio_pci_common.h"
 

@@ -271,9 +272,13 @@ static void vp_reset(struct virtio_devic
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	/* 0 status means a reset. */
 	vp_iowrite8(0, &vp_dev->common->device_status);
-	/* Flush out the status write, and flush in device writes,
-	 * including MSI-X interrupts, if any. */
-	vp_ioread8(&vp_dev->common->device_status);
+	/* After writing 0 to device_status, the driver MUST wait for a read of
+	 * device_status to return 0 before reinitializing the device.
+	 * This will flush out the status write, and flush in device writes,
+	 * including MSI-X interrupts, if any.
+	 */
+	while (vp_ioread8(&vp_dev->common->device_status))
+		msleep(1);
 	/* Flush pending VQ/configuration callbacks. */
 	vp_synchronize_vectors(vdev);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/tuntap-restore-default-qdisc.patch queue-4.4/virtio-virtio-1.0-cs04-spec-compliance-for-reset.patch