[Qemu-devel] [PATCH 06/12] virtio-scsi: always use dataplane path if ioeventfd is active

[Paolo Bonzini]

Override start_ioeventfd and stop_ioeventfd to start/stop the
whole dataplane logic.  This has some positive side effects:

- no need anymore for virtio_add_queue_aio (i.e. a revert of
  commit 1c627137c10ee2dcf59e0383ade8a9abfa2d4355)

- no need anymore to switch from generic ioeventfd handlers to
  dataplane

Signed-off-by: Paolo Bonzini <address@hidden>
---
 hw/scsi/virtio-scsi-dataplane.c | 51 ++++++++++++++++++++++++-----------------
 hw/scsi/virtio-scsi.c           | 24 +++++++++----------
 include/hw/virtio/virtio-scsi.h |  6 ++---
 3 files changed, 44 insertions(+), 37 deletions(-)

diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index f537b4e..619d796 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -12,6 +12,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/error.h"
 #include "hw/virtio/virtio-scsi.h"
 #include "qemu/error-report.h"
 #include "sysemu/block-backend.h"
@@ -21,20 +22,27 @@
 #include "hw/virtio/virtio-access.h"
 
 /* Context: QEMU global mutex held */
-void virtio_scsi_set_iothread(VirtIOSCSI *s, IOThread *iothread)
+void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp)
 {
-    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
-    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
+    VirtIODevice *vdev = VIRTIO_DEVICE(s);
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 
-    assert(!s->ctx);
-    s->ctx = iothread_get_aio_context(vs->conf.iothread);
+    if (!virtio_device_ioeventfd_enabled(vdev)) {
+        return;
+    }
 
-    /* Don't try if transport does not support notifiers. */
-    if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
-        fprintf(stderr, "virtio-scsi: Failed to set iothread "
-                   "(transport does not support notifiers)");
-        exit(1);
+    if (vs->conf.iothread) {
+        if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
+            error_setg(errp,
+                       "device is incompatible with dataplane "
+                       "(transport does not support notifiers)");
+            return;
+        }
+        s->ctx = iothread_get_aio_context(vs->conf.iothread);
+    } else {
+        s->ctx = qemu_get_aio_context();
     }
 }
 
@@ -105,19 +113,19 @@ static void virtio_scsi_clear_aio(VirtIOSCSI *s)
 }
 
 /* Context: QEMU global mutex held */
-void virtio_scsi_dataplane_start(VirtIOSCSI *s)
+int virtio_scsi_dataplane_start(VirtIODevice *vdev)
 {
     int i;
     int rc;
-    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
-    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
+    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
+    VirtIOSCSI *s = VIRTIO_SCSI(vdev);
 
     if (s->dataplane_started ||
         s->dataplane_starting ||
-        s->dataplane_fenced ||
-        s->ctx != iothread_get_aio_context(vs->conf.iothread)) {
-        return;
+        s->dataplane_fenced) {
+        return 0;
     }
 
     s->dataplane_starting = true;
@@ -152,7 +160,7 @@ void virtio_scsi_dataplane_start(VirtIOSCSI *s)
     s->dataplane_starting = false;
     s->dataplane_started = true;
     aio_context_release(s->ctx);
-    return;
+    return 0;
 
 fail_vrings:
     virtio_scsi_clear_aio(s);
@@ -165,14 +173,16 @@ fail_guest_notifiers:
     s->dataplane_fenced = true;
     s->dataplane_starting = false;
     s->dataplane_started = true;
+    return -ENOSYS;
 }
 
 /* Context: QEMU global mutex held */
-void virtio_scsi_dataplane_stop(VirtIOSCSI *s)
+void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
 {
-    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
-    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
+    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
+    VirtIOSCSI *s = VIRTIO_SCSI(vdev);
     int i;
 
     if (!s->dataplane_started || s->dataplane_stopping) {
@@ -186,7 +196,6 @@ void virtio_scsi_dataplane_stop(VirtIOSCSI *s)
         return;
     }
     s->dataplane_stopping = true;
-    assert(s->ctx == iothread_get_aio_context(vs->conf.iothread));
 
     aio_context_acquire(s->ctx);
 
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index ce57ef6..e8eda7c 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -426,7 +426,7 @@ static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, 
VirtQueue *vq)
     VirtIOSCSI *s = (VirtIOSCSI *)vdev;
 
     if (s->ctx) {
-        virtio_scsi_dataplane_start(s);
+        virtio_device_start_ioeventfd(vdev);
         if (!s->dataplane_fenced) {
             return;
         }
@@ -590,7 +590,7 @@ static void virtio_scsi_handle_cmd(VirtIODevice *vdev, 
VirtQueue *vq)
     VirtIOSCSI *s = (VirtIOSCSI *)vdev;
 
     if (s->ctx) {
-        virtio_scsi_dataplane_start(s);
+        virtio_device_start_ioeventfd(vdev);
         if (!s->dataplane_fenced) {
             return;
         }
@@ -648,9 +648,7 @@ static void virtio_scsi_reset(VirtIODevice *vdev)
     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
 
-    if (s->ctx) {
-        virtio_scsi_dataplane_stop(s);
-    }
+    assert(!s->dataplane_started);
     s->resetting++;
     qbus_reset_all(&s->bus.qbus);
     s->resetting--;
@@ -743,7 +741,7 @@ static void virtio_scsi_handle_event(VirtIODevice *vdev, 
VirtQueue *vq)
     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
 
     if (s->ctx) {
-        virtio_scsi_dataplane_start(s);
+        virtio_device_start_ioeventfd(vdev);
         if (!s->dataplane_fenced) {
             return;
         }
@@ -842,14 +840,10 @@ void virtio_scsi_common_realize(DeviceState *dev, Error 
**errp,
     s->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE;
     s->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE;
 
-    s->ctrl_vq = virtio_add_queue_aio(vdev, VIRTIO_SCSI_VQ_SIZE, ctrl);
-    s->event_vq = virtio_add_queue_aio(vdev, VIRTIO_SCSI_VQ_SIZE, evt);
+    s->ctrl_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, ctrl);
+    s->event_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, evt);
     for (i = 0; i < s->conf.num_queues; i++) {
-        s->cmd_vqs[i] = virtio_add_queue_aio(vdev, VIRTIO_SCSI_VQ_SIZE, cmd);
-    }
-
-    if (s->conf.iothread) {
-        virtio_scsi_set_iothread(VIRTIO_SCSI(s), s->conf.iothread);
+        s->cmd_vqs[i] = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, cmd);
     }
 }
 
@@ -879,6 +873,8 @@ static void virtio_scsi_device_realize(DeviceState *dev, 
Error **errp)
             return;
         }
     }
+
+    virtio_scsi_dataplane_setup(s, errp);
 }
 
 static void virtio_scsi_instance_init(Object *obj)
@@ -943,6 +939,8 @@ static void virtio_scsi_class_init(ObjectClass *klass, void 
*data)
     vdc->set_config = virtio_scsi_set_config;
     vdc->get_features = virtio_scsi_get_features;
     vdc->reset = virtio_scsi_reset;
+    vdc->start_ioeventfd = virtio_scsi_dataplane_start;
+    vdc->stop_ioeventfd = virtio_scsi_dataplane_stop;
     hc->plug = virtio_scsi_hotplug;
     hc->unplug = virtio_scsi_hotunplug;
 }
diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
index a1e0cfb..9fbc7d7 100644
--- a/include/hw/virtio/virtio-scsi.h
+++ b/include/hw/virtio/virtio-scsi.h
@@ -134,9 +134,9 @@ void virtio_scsi_free_req(VirtIOSCSIReq *req);
 void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
                             uint32_t event, uint32_t reason);
 
-void virtio_scsi_set_iothread(VirtIOSCSI *s, IOThread *iothread);
-void virtio_scsi_dataplane_start(VirtIOSCSI *s);
-void virtio_scsi_dataplane_stop(VirtIOSCSI *s);
+void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp);
+int virtio_scsi_dataplane_start(VirtIODevice *s);
+void virtio_scsi_dataplane_stop(VirtIODevice *s);
 void virtio_scsi_dataplane_notify(VirtIODevice *vdev, VirtIOSCSIReq *req);
 
 #endif /* QEMU_VIRTIO_SCSI_H */
-- 
2.7.4