[Qemu-devel] [PATCH 14/40] virtio-blk: do not use vring in dataplane

[Paolo Bonzini <pbonzini@redhat.com>]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/block/dataplane/virtio-blk.c | 112 +++++-----------------------------------
 hw/block/dataplane/virtio-blk.h |   1 +
 hw/block/virtio-blk.c           |  48 +++--------------
 include/hw/virtio/virtio-blk.h  |   3 --
 4 files changed, 19 insertions(+), 145 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 8d417e2..f2482eb 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -17,8 +17,6 @@
 #include "qemu/thread.h"
 #include "qemu/error-report.h"
 #include "hw/virtio/virtio-access.h"
-#include "hw/virtio/dataplane/vring.h"
-#include "hw/virtio/dataplane/vring-accessors.h"
 #include "sysemu/block-backend.h"
 #include "hw/virtio/virtio-blk.h"
 #include "virtio-blk.h"
@@ -34,7 +32,7 @@ struct VirtIOBlockDataPlane {
     VirtIOBlkConf *conf;
 
     VirtIODevice *vdev;
-    Vring vring;                    /* virtqueue vring */
+    VirtQueue *vq;                  /* virtqueue vring */
     EventNotifier *guest_notifier;  /* irq */
     QEMUBH *bh;                     /* bh for guest notification */
 
@@ -46,94 +44,26 @@ struct VirtIOBlockDataPlane {
     IOThread *iothread;
     IOThread internal_iothread_obj;
     AioContext *ctx;
-    EventNotifier host_notifier;    /* doorbell */
 
     /* Operation blocker on BDS */
     Error *blocker;
-    void (*saved_complete_request)(struct VirtIOBlockReq *req,
-                                   unsigned char status);
 };
 
 /* Raise an interrupt to signal guest, if necessary */
-static void notify_guest(VirtIOBlockDataPlane *s)
+void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s)
 {
-    if (!vring_should_notify(s->vdev, &s->vring)) {
-        return;
-    }
-
-    event_notifier_set(s->guest_notifier);
+    qemu_bh_schedule(s->bh);
 }
 
 static void notify_guest_bh(void *opaque)
 {
     VirtIOBlockDataPlane *s = opaque;
 
-    notify_guest(s);
-}
-
-static void complete_request_vring(VirtIOBlockReq *req, unsigned char status)
-{
-    VirtIOBlockDataPlane *s = req->dev->dataplane;
-    stb_p(&req->in->status, status);
-
-    vring_push(s->vdev, &req->dev->dataplane->vring, &req->elem, req->in_len);
-
-    /* Suppress notification to guest by BH and its scheduled
-     * flag because requests are completed as a batch after io
-     * plug & unplug is introduced, and the BH can still be
-     * executed in dataplane aio context even after it is
-     * stopped, so needn't worry about notification loss with BH.
-     */
-    qemu_bh_schedule(s->bh);
-}
-
-static void handle_notify(EventNotifier *e)
-{
-    VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
-                                           host_notifier);
-    VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
-
-    event_notifier_test_and_clear(&s->host_notifier);
-    blk_io_plug(s->conf->conf.blk);
-    for (;;) {
-        MultiReqBuffer mrb = {};
-
-        /* Disable guest->host notifies to avoid unnecessary vmexits */
-        vring_disable_notification(s->vdev, &s->vring);
-
-        for (;;) {
-            VirtIOBlockReq *req = vring_pop(s->vdev, &s->vring,
-                                            sizeof(VirtIOBlockReq));
-
-            if (req == NULL) {
-                break; /* no more requests */
-            }
-
-            virtio_blk_init_request(vblk, req);
-            trace_virtio_blk_data_plane_process_request(s, req->elem.out_num,
-                                                        req->elem.in_num,
-                                                        req->elem.index);
-
-            virtio_blk_handle_request(req, &mrb);
-        }
-
-        if (mrb.num_reqs) {
-            virtio_blk_submit_multireq(s->conf->conf.blk, &mrb);
-        }
-
-        if (likely(!vring_more_avail(s->vdev, &s->vring))) { /* vring emptied */
-            /* Re-enable guest->host notifies and stop processing the vring.
-             * But if the guest has snuck in more descriptors, keep processing.
-             */
-            vring_enable_notification(s->vdev, &s->vring);
-            if (!vring_more_avail(s->vdev, &s->vring)) {
-                break;
-            }
-        } else { /* fatal error */
-            break;
-        }
+    if (!virtio_should_notify(s->vdev, s->vq)) {
+        return;
     }
-    blk_io_unplug(s->conf->conf.blk);
+
+    event_notifier_set(s->guest_notifier);
 }
 
 /* Context: QEMU global mutex held */
@@ -233,7 +163,6 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
-    VirtQueue *vq;
     int r;
 
     if (vblk->dataplane_started || s->starting) {
@@ -241,11 +170,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     }
 
     s->starting = true;
-
-    vq = virtio_get_queue(s->vdev, 0);
-    if (!vring_setup(&s->vring, s->vdev, 0)) {
-        goto fail_vring;
-    }
+    s->vq = virtio_get_queue(s->vdev, 0);
 
     /* Set up guest notifier (irq) */
     r = k->set_guest_notifiers(qbus->parent, 1, true);
@@ -254,7 +179,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
                 "ensure -enable-kvm is set\n", r);
         goto fail_guest_notifiers;
     }
-    s->guest_notifier = virtio_queue_get_guest_notifier(vq);
+    s->guest_notifier = virtio_queue_get_guest_notifier(s->vq);
 
     /* Set up virtqueue notify */
     r = k->set_host_notifier(qbus->parent, 0, true);
@@ -262,10 +187,6 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
         fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
         goto fail_host_notifier;
     }
-    s->host_notifier = *virtio_queue_get_host_notifier(vq);
-
-    s->saved_complete_request = vblk->complete_request;
-    vblk->complete_request = complete_request_vring;
 
     s->starting = false;
     vblk->dataplane_started = true;
@@ -274,20 +195,17 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     blk_set_aio_context(s->conf->conf.blk, s->ctx);
 
     /* Kick right away to begin processing requests already in vring */
-    event_notifier_set(virtio_queue_get_host_notifier(vq));
+    event_notifier_set(virtio_queue_get_host_notifier(s->vq));
 
     /* Get this show started by hooking up our callbacks */
     aio_context_acquire(s->ctx);
-    aio_set_event_notifier(s->ctx, &s->host_notifier, true,
-                           handle_notify);
+    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, true, true);
     aio_context_release(s->ctx);
     return;
 
   fail_host_notifier:
     k->set_guest_notifiers(qbus->parent, 1, false);
   fail_guest_notifiers:
-    vring_teardown(&s->vring, s->vdev, 0);
-  fail_vring:
     s->disabled = true;
     s->starting = false;
     vblk->dataplane_started = true;
@@ -311,24 +229,18 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
         return;
     }
     s->stopping = true;
-    vblk->complete_request = s->saved_complete_request;
     trace_virtio_blk_data_plane_stop(s);
 
     aio_context_acquire(s->ctx);
 
     /* Stop notifications for new requests from guest */
-    aio_set_event_notifier(s->ctx, &s->host_notifier, true, NULL);
+    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, false, false);
 
     /* Drain and switch bs back to the QEMU main loop */
     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
 
     aio_context_release(s->ctx);
 
-    /* Sync vring state back to virtqueue so that non-dataplane request
-     * processing can continue when we disable the host notifier below.
-     */
-    vring_teardown(&s->vring, s->vdev, 0);
-
     k->set_host_notifier(qbus->parent, 0, false);
 
     /* Clean up guest notifier (irq) */
diff --git a/hw/block/dataplane/virtio-blk.h b/hw/block/dataplane/virtio-blk.h
index c88d40e..0714c11 100644
--- a/hw/block/dataplane/virtio-blk.h
+++ b/hw/block/dataplane/virtio-blk.h
@@ -26,5 +26,6 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s);
 void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s);
 void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s);
 void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s);
+void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s);
 
 #endif /* HW_DATAPLANE_VIRTIO_BLK_H */
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 062d57e..e83d823 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -44,8 +44,7 @@ void virtio_blk_free_request(VirtIOBlockReq *req)
     }
 }
 
-static void virtio_blk_complete_request(VirtIOBlockReq *req,
-                                        unsigned char status)
+static void virtio_blk_req_complete(VirtIOBlockReq *req, unsigned char status)
 {
     VirtIOBlock *s = req->dev;
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
@@ -54,12 +53,11 @@ static void virtio_blk_complete_request(VirtIOBlockReq *req,
 
     stb_p(&req->in->status, status);
     virtqueue_push(s->vq, &req->elem, req->in_len);
-    virtio_notify(vdev, s->vq);
-}
-
-static void virtio_blk_req_complete(VirtIOBlockReq *req, unsigned char status)
-{
-    req->dev->complete_request(req, status);
+    if (s->dataplane) {
+        virtio_blk_data_plane_notify(s->dataplane);
+    } else {
+        virtio_notify(vdev, s->vq);
+    }
 }
 
 static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
@@ -859,36 +857,6 @@ static const BlockDevOps virtio_block_ops = {
     .resize_cb = virtio_blk_resize,
 };
 
-/* Disable dataplane thread during live migration since it does not
- * update the dirty memory bitmap yet.
- */
-static void virtio_blk_migration_state_changed(Notifier *notifier, void *data)
-{
-    VirtIOBlock *s = container_of(notifier, VirtIOBlock,
-                                  migration_state_notifier);
-    MigrationState *mig = data;
-    Error *err = NULL;
-
-    if (migration_in_setup(mig)) {
-        if (!s->dataplane) {
-            return;
-        }
-        virtio_blk_data_plane_destroy(s->dataplane);
-        s->dataplane = NULL;
-    } else if (migration_has_finished(mig) ||
-               migration_has_failed(mig)) {
-        if (s->dataplane) {
-            return;
-        }
-        blk_drain_all(); /* complete in-flight non-dataplane requests */
-        virtio_blk_data_plane_create(VIRTIO_DEVICE(s), &s->conf,
-                                     &s->dataplane, &err);
-        if (err != NULL) {
-            error_report_err(err);
-        }
-    }
-}
-
 static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
@@ -923,15 +891,12 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
     s->sector_mask = (s->conf.conf.logical_block_size / BDRV_SECTOR_SIZE) - 1;
 
     s->vq = virtio_add_queue(vdev, 128, virtio_blk_handle_output);
-    s->complete_request = virtio_blk_complete_request;
     virtio_blk_data_plane_create(vdev, conf, &s->dataplane, &err);
     if (err != NULL) {
         error_propagate(errp, err);
         virtio_cleanup(vdev);
         return;
     }
-    s->migration_state_notifier.notify = virtio_blk_migration_state_changed;
-    add_migration_state_change_notifier(&s->migration_state_notifier);
 
     s->change = qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
     register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
@@ -947,7 +912,6 @@ static void virtio_blk_device_unrealize(DeviceState *dev, Error **errp)
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VirtIOBlock *s = VIRTIO_BLK(dev);
 
-    remove_migration_state_change_notifier(&s->migration_state_notifier);
     virtio_blk_data_plane_destroy(s->dataplane);
     s->dataplane = NULL;
     qemu_del_vm_change_state_handler(s->change);
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index e720934..4c72021 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -54,9 +54,6 @@ typedef struct VirtIOBlock {
     unsigned short sector_mask;
     bool original_wce;
     VMChangeStateEntry *change;
-    /* Function to push to vq and notify guest */
-    void (*complete_request)(struct VirtIOBlockReq *req, unsigned char status);
-    Notifier migration_state_notifier;
     bool dataplane_started;
     struct VirtIOBlockDataPlane *dataplane;
 } VirtIOBlock;
-- 
1.8.3.1