virtio-pci: support queue reset

PCI devices support vq reset.

Based on this function, the driver can adjust the size of the ring, and
quickly recycle the buffer in the ring.

The migration of the virtio devices will not happen during a reset
operation. This is becuase the global iothread lock is held. Migration
thread also needs the lock. As a result, when migration of virtio
devices starts, the 'reset' status of VirtIOPCIQueue will always be 0.
Thus, we do not need to add it in vmstate_virtio_pci_modern_queue_state.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20221017092558.111082-6-xuanzhuo@linux.alibaba.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 34db51e241..d4f2ffe986 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1251,6 +1251,9 @@ static uint64_t virtio_pci_common_read(void *opaque, hwaddr addr,
     case VIRTIO_PCI_COMMON_Q_USEDHI:
         val = proxy->vqs[vdev->queue_sel].used[1];
         break;
+    case VIRTIO_PCI_COMMON_Q_RESET:
+        val = proxy->vqs[vdev->queue_sel].reset;
+        break;
     default:
         val = 0;
     }
@@ -1338,6 +1341,7 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
                        ((uint64_t)proxy->vqs[vdev->queue_sel].used[1]) << 32 |
                        proxy->vqs[vdev->queue_sel].used[0]);
             proxy->vqs[vdev->queue_sel].enabled = 1;
+            proxy->vqs[vdev->queue_sel].reset = 0;
         } else {
             virtio_error(vdev, "wrong value for queue_enable %"PRIx64, val);
         }
@@ -1360,6 +1364,16 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
     case VIRTIO_PCI_COMMON_Q_USEDHI:
         proxy->vqs[vdev->queue_sel].used[1] = val;
         break;
+    case VIRTIO_PCI_COMMON_Q_RESET:
+        if (val == 1) {
+            proxy->vqs[vdev->queue_sel].reset = 1;
+
+            virtio_queue_reset(vdev, vdev->queue_sel);
+
+            proxy->vqs[vdev->queue_sel].reset = 0;
+            proxy->vqs[vdev->queue_sel].enabled = 0;
+        }
+        break;
     default:
         break;
     }
@@ -1954,6 +1968,7 @@ static void virtio_pci_reset(DeviceState *qdev)
 
     for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
         proxy->vqs[i].enabled = 0;
+        proxy->vqs[i].reset = 0;
         proxy->vqs[i].num = 0;
         proxy->vqs[i].desc[0] = proxy->vqs[i].desc[1] = 0;
         proxy->vqs[i].avail[0] = proxy->vqs[i].avail[1] = 0;