Virtualization - Apr 2016 - [PATCH] virtio: virtio 1.0 cs04 spec compliance for reset

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.

Cc: stable at vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 drivers/virtio/virtio_pci_modern.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern.c
b/drivers/virtio/virtio_pci_modern.c
index f6f28cc..e76bd91 100644
--- 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_device *vdev)
 	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);
 }
-- 
MST

On 04/03/2016 08:26 PM, Michael S. Tsirkin wrote:
> 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.
>
> Cc: stable at vger.kernel.org
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
>  drivers/virtio/virtio_pci_modern.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_modern.c
b/drivers/virtio/virtio_pci_modern.c
> index f6f28cc..e76bd91 100644
> --- 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_device *vdev)
>  	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);
>  }
Acked-by: Jason Wang <jasowang at redhat.com>