[RFC 1/8] virtio/virtio-pci: Handle extra notification data

[Jonah Palmer]

Add support to virtio-pci devices for handling the extra data sent
from the driver to the device when the VIRTIO_F_NOTIFICATION_DATA
transport feature has been negotiated.

The extra data that's passed to the virtio-pci device when this
feature is enabled varies depending on the device's virtqueue
layout.

In a split virtqueue layout, this data includes:
 - upper 16 bits: last_avail_idx
 - lower 16 bits: virtqueue index

In a packed virtqueue layout, this data includes:
 - upper 16 bits: 1-bit wrap counter & 15-bit last_avail_idx
 - lower 16 bits: virtqueue index

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
---
 hw/virtio/virtio-pci.c     | 13 ++++++++++---
 hw/virtio/virtio.c         | 13 +++++++++++++
 include/hw/virtio/virtio.h |  1 +
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 1a7039fb0c..c7c577b177 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -384,7 +384,7 @@ static void virtio_ioport_write(void *opaque, uint32_t 
addr, uint32_t val)
 {
     VirtIOPCIProxy *proxy = opaque;
     VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
-    uint16_t vector;
+    uint16_t vector, vq_idx;
     hwaddr pa;
 
     switch (addr) {
@@ -408,8 +408,15 @@ static void virtio_ioport_write(void *opaque, uint32_t 
addr, uint32_t val)
             vdev->queue_sel = val;
         break;
     case VIRTIO_PCI_QUEUE_NOTIFY:
-        if (val < VIRTIO_QUEUE_MAX) {
-            virtio_queue_notify(vdev, val);
+        if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
+            vq_idx = val & 0xFFFF;
+            virtio_set_notification_data(vdev, vq_idx, val);
+        } else {
+            vq_idx = val;
+        }
+
+        if (vq_idx < VIRTIO_QUEUE_MAX) {
+            virtio_queue_notify(vdev, vq_idx);
         }
         break;
     case VIRTIO_PCI_STATUS:
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index d229755eae..a61f69b7fd 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2052,6 +2052,19 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val)
     return 0;
 }
 
+void virtio_set_notification_data(VirtIODevice *vdev, uint16_t i, uint32_t 
data)
+{
+    VirtQueue *vq = &vdev->vq[i];
+
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+        vq->last_avail_wrap_counter = (data >> 31) & 0x1;
+        vq->last_avail_idx = (data >> 16) & 0x7FFF;
+    } else {
+        vq->last_avail_idx = (data >> 16) & 0xFFFF;
+    }
+    vq->shadow_avail_idx = vq->last_avail_idx;
+}
+
 static enum virtio_device_endian virtio_default_endian(void)
 {
     if (target_words_bigendian()) {
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index c8f72850bc..c92d8afc42 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -345,6 +345,7 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t 
queue_index);
 void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index);
 void virtio_update_irq(VirtIODevice *vdev);
 int virtio_set_features(VirtIODevice *vdev, uint64_t val);
+void virtio_set_notification_data(VirtIODevice *vdev, uint16_t i, uint32_t 
data);
 
 /* Base devices.  */
 typedef struct VirtIOBlkConf VirtIOBlkConf;
-- 
2.39.3