[PATCH v2 06/24] virtio-pci: support queue reset

[Kangjie Xu]

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

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, we do not need to migrate the
reset state of VirtIOPCIQueue.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
---
 hw/virtio/virtio-pci.c         | 19 +++++++++++++++++++
 include/hw/virtio/virtio-pci.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 45327f0b31..ec8e92052f 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1246,6 +1246,9 @@ 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;
     }
@@ -1333,6 +1336,7 @@ 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);
         }
@@ -1355,6 +1359,20 @@ 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) {
+            /*
+             * With the global iothread lock taken, the migration will not
+             * happen until the virtqueue reset is done.
+             */
+            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;
     }
@@ -1950,6 +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;
diff --git a/include/hw/virtio/virtio-pci.h b/include/hw/virtio/virtio-pci.h
index 2446dcd9ae..e9290e2b94 100644
--- a/include/hw/virtio/virtio-pci.h
+++ b/include/hw/virtio/virtio-pci.h
@@ -117,6 +117,7 @@ typedef struct VirtIOPCIRegion {
 typedef struct VirtIOPCIQueue {
   uint16_t num;
   bool enabled;
+  bool reset;
   uint32_t desc[2];
   uint32_t avail[2];
   uint32_t used[2];
-- 
2.32.0