[PATCH 3/6] vhost: Do not reset suspended devices on stop

[Hanna Czenczek]

Move the `suspended` field from vhost_vdpa into the global vhost_dev
struct, so vhost_dev_stop() can check whether the back-end has been
suspended by `vhost_ops->vhost_dev_start(hdev, false)`.  If it has,
there is no need to reset it; the reset is just a fall-back to stop
device operations for back-ends that do not support suspend.

Unfortunately, for vDPA specifically, RESUME is not yet implemented, so
when the device is re-started, we still have to do the reset to have it
un-suspend.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
---
 include/hw/virtio/vhost-vdpa.h |  2 --
 include/hw/virtio/vhost.h      |  8 ++++++++
 hw/virtio/vhost-vdpa.c         | 11 +++++++----
 hw/virtio/vhost.c              |  8 +++++++-
 4 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index e64bfc7f98..72c3686b7f 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -42,8 +42,6 @@ typedef struct vhost_vdpa {
     bool shadow_vqs_enabled;
     /* Vdpa must send shadow addresses as IOTLB key for data queues, not GPA */
     bool shadow_data;
-    /* Device suspended successfully */
-    bool suspended;
     /* IOVA mapping used by the Shadow Virtqueue */
     VhostIOVATree *iova_tree;
     GPtrArray *shadow_vqs;
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 6a173cb9fa..69bf59d630 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -120,6 +120,14 @@ struct vhost_dev {
     uint64_t backend_cap;
     /* @started: is the vhost device started? */
     bool started;
+    /**
+     * @suspended: Whether the vhost device is currently suspended.  Set
+     * and reset by implementations (vhost-user, vhost-vdpa, ...), which
+     * are supposed to automatically suspend/resume in their
+     * vhost_dev_start handlers as required.  Must also be cleared when
+     * the device is reset.
+     */
+    bool suspended;
     bool log_enabled;
     uint64_t log_size;
     Error *migration_blocker;
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 7b7dee468e..f7fd19a203 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -858,13 +858,12 @@ static int vhost_vdpa_get_device_id(struct vhost_dev *dev,
 
 static int vhost_vdpa_reset_device(struct vhost_dev *dev)
 {
-    struct vhost_vdpa *v = dev->opaque;
     int ret;
     uint8_t status = 0;
 
     ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &status);
     trace_vhost_vdpa_reset_device(dev);
-    v->suspended = false;
+    dev->suspended = false;
     return ret;
 }
 
@@ -1278,7 +1277,7 @@ static void vhost_vdpa_suspend(struct vhost_dev *dev)
         if (unlikely(r)) {
             error_report("Cannot suspend: %s(%d)", g_strerror(errno), errno);
         } else {
-            v->suspended = true;
+            dev->suspended = true;
             return;
         }
     }
@@ -1313,6 +1312,10 @@ static int vhost_vdpa_dev_start(struct vhost_dev *dev, 
bool started)
             return -1;
         }
         vhost_vdpa_set_vring_ready(dev);
+        if (dev->suspended) {
+            /* TODO: When RESUME is available, use it instead of resetting */
+            vhost_vdpa_reset_status(dev);
+        }
     } else {
         vhost_vdpa_suspend(dev);
         vhost_vdpa_svqs_stop(dev);
@@ -1400,7 +1403,7 @@ static int vhost_vdpa_get_vring_base(struct vhost_dev 
*dev,
         return 0;
     }
 
-    if (!v->suspended) {
+    if (!dev->suspended) {
         /*
          * Cannot trust in value returned by device, let vhost recover used
          * idx from guest.
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index abf0d03c8d..2e28e58da7 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -2059,7 +2059,13 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice 
*vdev, bool vrings)
                              hdev->vqs + i,
                              hdev->vq_index + i);
     }
-    if (hdev->vhost_ops->vhost_reset_status) {
+
+    /*
+     * If we failed to successfully stop the device via SUSPEND (should have
+     * been attempted by `vhost_dev_start(hdev, false)`), reset it to stop it.
+     * Stateful devices where this would be problematic must implement SUSPEND.
+     */
+    if (!hdev->suspended && hdev->vhost_ops->vhost_reset_status) {
         hdev->vhost_ops->vhost_reset_status(hdev);
     }
 
-- 
2.41.0