From: Jonah Palmer <jonah.palmer@oracle.com>

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: shadow_avail_idx
 - lower 16 bits: virtqueue index

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

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <20240315165557.26942-2-jonah.palmer@oracle.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/virtio.h |  2 ++
 hw/virtio/virtio-pci.c     | 12 +++++++++---
 hw/virtio/virtio.c         | 18 ++++++++++++++++++
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 7d5ffdc145..1451926a13 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -307,6 +307,8 @@ int virtio_queue_ready(VirtQueue *vq);
 
 int virtio_queue_empty(VirtQueue *vq);
 
+void virtio_queue_set_shadow_avail_idx(VirtQueue *vq, uint16_t idx);
+
 /* Host binding interface.  */
 
 uint32_t virtio_config_readb(VirtIODevice *vdev, uint32_t addr);
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index a7faee5b33..ad0035952f 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 +408,14 @@ 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);
+        vq_idx = val;
+        if (vq_idx < VIRTIO_QUEUE_MAX && virtio_queue_get_num(vdev, vq_idx)) {
+            if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
+                VirtQueue *vq = virtio_get_queue(vdev, vq_idx);
+
+                virtio_queue_set_shadow_avail_idx(vq, val >> 16);
+            }
+            virtio_queue_notify(vdev, vq_idx);
         }
         break;
     case VIRTIO_PCI_STATUS:
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 893a072c9d..f7c99e3a96 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2264,6 +2264,24 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
     }
 }
 
+void virtio_queue_set_shadow_avail_idx(VirtQueue *vq, uint16_t shadow_avail_idx)
+{
+    if (!vq->vring.desc) {
+        return;
+    }
+
+    /*
+     * 16-bit data for packed VQs include 1-bit wrap counter and
+     * 15-bit shadow_avail_idx.
+     */
+    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
+        vq->shadow_avail_wrap_counter = (shadow_avail_idx >> 15) & 0x1;
+        vq->shadow_avail_idx = shadow_avail_idx & 0x7FFF;
+    } else {
+        vq->shadow_avail_idx = shadow_avail_idx;
+    }
+}
+
 static void virtio_queue_notify_vq(VirtQueue *vq)
 {
     if (vq->vring.desc && vq->handle_output) {
-- 
MST