[PATCH 4.4 097/137] virtio: virtio 1.0 cs04 spec compliance for reset

From: Greg Kroah-Hartman
Date: Sun Apr 17 2016 - 22:39:13 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Michael S. Tsirkin <mst@xxxxxxxxxx>

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.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -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);
}