hw: move virtio devices to hw/ subdirectories

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

5 files changed, 744 insertions, 0 deletions

diff --git a/hw/block/dataplane/Makefile.objs b/hw/block/dataplane/Makefile.objs
new file mode 100644
index 0000000000..9da2eb82ba
--- /dev/null
+++ b/hw/block/dataplane/Makefile.objs
@@ -0,0 +1 @@
+obj-y += ioq.o virtio-blk.o
diff --git a/hw/block/dataplane/ioq.c b/hw/block/dataplane/ioq.c
new file mode 100644
index 0000000000..f709f87ed6
--- /dev/null
+++ b/hw/block/dataplane/ioq.c
@@ -0,0 +1,117 @@
+/*
+ * Linux AIO request queue
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *   Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "ioq.h"
+
+void ioq_init(IOQueue *ioq, int fd, unsigned int max_reqs)
+{
+    int rc;
+
+    ioq->fd = fd;
+    ioq->max_reqs = max_reqs;
+
+    memset(&ioq->io_ctx, 0, sizeof ioq->io_ctx);
+    rc = io_setup(max_reqs, &ioq->io_ctx);
+    if (rc != 0) {
+        fprintf(stderr, "ioq io_setup failed %d\n", rc);
+        exit(1);
+    }
+
+    rc = event_notifier_init(&ioq->io_notifier, 0);
+    if (rc != 0) {
+        fprintf(stderr, "ioq io event notifier creation failed %d\n", rc);
+        exit(1);
+    }
+
+    ioq->freelist = g_malloc0(sizeof ioq->freelist[0] * max_reqs);
+    ioq->freelist_idx = 0;
+
+    ioq->queue = g_malloc0(sizeof ioq->queue[0] * max_reqs);
+    ioq->queue_idx = 0;
+}
+
+void ioq_cleanup(IOQueue *ioq)
+{
+    g_free(ioq->freelist);
+    g_free(ioq->queue);
+
+    event_notifier_cleanup(&ioq->io_notifier);
+    io_destroy(ioq->io_ctx);
+}
+
+EventNotifier *ioq_get_notifier(IOQueue *ioq)
+{
+    return &ioq->io_notifier;
+}
+
+struct iocb *ioq_get_iocb(IOQueue *ioq)
+{
+    /* Underflow cannot happen since ioq is sized for max_reqs */
+    assert(ioq->freelist_idx != 0);
+
+    struct iocb *iocb = ioq->freelist[--ioq->freelist_idx];
+    ioq->queue[ioq->queue_idx++] = iocb;
+    return iocb;
+}
+
+void ioq_put_iocb(IOQueue *ioq, struct iocb *iocb)
+{
+    /* Overflow cannot happen since ioq is sized for max_reqs */
+    assert(ioq->freelist_idx != ioq->max_reqs);
+
+    ioq->freelist[ioq->freelist_idx++] = iocb;
+}
+
+struct iocb *ioq_rdwr(IOQueue *ioq, bool read, struct iovec *iov,
+                      unsigned int count, long long offset)
+{
+    struct iocb *iocb = ioq_get_iocb(ioq);
+
+    if (read) {
+        io_prep_preadv(iocb, ioq->fd, iov, count, offset);
+    } else {
+        io_prep_pwritev(iocb, ioq->fd, iov, count, offset);
+    }
+    io_set_eventfd(iocb, event_notifier_get_fd(&ioq->io_notifier));
+    return iocb;
+}
+
+int ioq_submit(IOQueue *ioq)
+{
+    int rc = io_submit(ioq->io_ctx, ioq->queue_idx, ioq->queue);
+    ioq->queue_idx = 0; /* reset */
+    return rc;
+}
+
+int ioq_run_completion(IOQueue *ioq, IOQueueCompletion *completion,
+                       void *opaque)
+{
+    struct io_event events[ioq->max_reqs];
+    int nevents, i;
+
+    do {
+        nevents = io_getevents(ioq->io_ctx, 0, ioq->max_reqs, events, NULL);
+    } while (nevents < 0 && errno == EINTR);
+    if (nevents < 0) {
+        return nevents;
+    }
+
+    for (i = 0; i < nevents; i++) {
+        ssize_t ret = ((uint64_t)events[i].res2 << 32) | events[i].res;
+
+        completion(events[i].obj, ret, opaque);
+        ioq_put_iocb(ioq, events[i].obj);
+    }
+    return nevents;
+}
diff --git a/hw/block/dataplane/ioq.h b/hw/block/dataplane/ioq.h
new file mode 100644
index 0000000000..b49b5de7f4
--- /dev/null
+++ b/hw/block/dataplane/ioq.h
@@ -0,0 +1,57 @@
+/*
+ * Linux AIO request queue
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *   Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef IOQ_H
+#define IOQ_H
+
+#include <libaio.h>
+#include "qemu/event_notifier.h"
+
+typedef struct {
+    int fd;                         /* file descriptor */
+    unsigned int max_reqs;          /* max length of freelist and queue */
+
+    io_context_t io_ctx;            /* Linux AIO context */
+    EventNotifier io_notifier;      /* Linux AIO eventfd */
+
+    /* Requests can complete in any order so a free list is necessary to manage
+     * available iocbs.
+     */
+    struct iocb **freelist;         /* free iocbs */
+    unsigned int freelist_idx;
+
+    /* Multiple requests are queued up before submitting them all in one go */
+    struct iocb **queue;            /* queued iocbs */
+    unsigned int queue_idx;
+} IOQueue;
+
+void ioq_init(IOQueue *ioq, int fd, unsigned int max_reqs);
+void ioq_cleanup(IOQueue *ioq);
+EventNotifier *ioq_get_notifier(IOQueue *ioq);
+struct iocb *ioq_get_iocb(IOQueue *ioq);
+void ioq_put_iocb(IOQueue *ioq, struct iocb *iocb);
+struct iocb *ioq_rdwr(IOQueue *ioq, bool read, struct iovec *iov,
+                      unsigned int count, long long offset);
+int ioq_submit(IOQueue *ioq);
+
+static inline unsigned int ioq_num_queued(IOQueue *ioq)
+{
+    return ioq->queue_idx;
+}
+
+typedef void IOQueueCompletion(struct iocb *iocb, ssize_t ret, void *opaque);
+int ioq_run_completion(IOQueue *ioq, IOQueueCompletion *completion,
+                       void *opaque);
+
+#endif /* IOQ_H */
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
new file mode 100644
index 0000000000..5baef2391a
--- /dev/null
+++ b/hw/block/dataplane/virtio-blk.c
@@ -0,0 +1,540 @@
+/*
+ * Dedicated thread for virtio-blk I/O processing
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *   Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "trace.h"
+#include "qemu/iov.h"
+#include "qemu/thread.h"
+#include "qemu/error-report.h"
+#include "hw/virtio/dataplane/vring.h"
+#include "ioq.h"
+#include "migration/migration.h"
+#include "block/block.h"
+#include "hw/virtio/virtio-blk.h"
+#include "virtio-blk.h"
+#include "block/aio.h"
+
+enum {
+    SEG_MAX = 126,                  /* maximum number of I/O segments */
+    VRING_MAX = SEG_MAX + 2,        /* maximum number of vring descriptors */
+    REQ_MAX = VRING_MAX,            /* maximum number of requests in the vring,
+                                     * is VRING_MAX / 2 with traditional and
+                                     * VRING_MAX with indirect descriptors */
+};
+
+typedef struct {
+    struct iocb iocb;               /* Linux AIO control block */
+    QEMUIOVector *inhdr;            /* iovecs for virtio_blk_inhdr */
+    unsigned int head;              /* vring descriptor index */
+    struct iovec *bounce_iov;       /* used if guest buffers are unaligned */
+    QEMUIOVector *read_qiov;        /* for read completion /w bounce buffer */
+} VirtIOBlockRequest;
+
+struct VirtIOBlockDataPlane {
+    bool started;
+    bool stopping;
+    QEMUBH *start_bh;
+    QemuThread thread;
+
+    VirtIOBlkConf *blk;
+    int fd;                         /* image file descriptor */
+
+    VirtIODevice *vdev;
+    Vring vring;                    /* virtqueue vring */
+    EventNotifier *guest_notifier;  /* irq */
+
+    /* Note that these EventNotifiers are assigned by value.  This is
+     * fine as long as you do not call event_notifier_cleanup on them
+     * (because you don't own the file descriptor or handle; you just
+     * use it).
+     */
+    AioContext *ctx;
+    EventNotifier io_notifier;      /* Linux AIO completion */
+    EventNotifier host_notifier;    /* doorbell */
+
+    IOQueue ioqueue;                /* Linux AIO queue (should really be per
+                                       dataplane thread) */
+    VirtIOBlockRequest requests[REQ_MAX]; /* pool of requests, managed by the
+                                             queue */
+
+    unsigned int num_reqs;
+
+    Error *migration_blocker;
+};
+
+/* Raise an interrupt to signal guest, if necessary */
+static void notify_guest(VirtIOBlockDataPlane *s)
+{
+    if (!vring_should_notify(s->vdev, &s->vring)) {
+        return;
+    }
+
+    event_notifier_set(s->guest_notifier);
+}
+
+static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque)
+{
+    VirtIOBlockDataPlane *s = opaque;
+    VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
+    struct virtio_blk_inhdr hdr;
+    int len;
+
+    if (likely(ret >= 0)) {
+        hdr.status = VIRTIO_BLK_S_OK;
+        len = ret;
+    } else {
+        hdr.status = VIRTIO_BLK_S_IOERR;
+        len = 0;
+    }
+
+    trace_virtio_blk_data_plane_complete_request(s, req->head, ret);
+
+    if (req->read_qiov) {
+        assert(req->bounce_iov);
+        qemu_iovec_from_buf(req->read_qiov, 0, req->bounce_iov->iov_base, len);
+        qemu_iovec_destroy(req->read_qiov);
+        g_slice_free(QEMUIOVector, req->read_qiov);
+    }
+
+    if (req->bounce_iov) {
+        qemu_vfree(req->bounce_iov->iov_base);
+        g_slice_free(struct iovec, req->bounce_iov);
+    }
+
+    qemu_iovec_from_buf(req->inhdr, 0, &hdr, sizeof(hdr));
+    qemu_iovec_destroy(req->inhdr);
+    g_slice_free(QEMUIOVector, req->inhdr);
+
+    /* According to the virtio specification len should be the number of bytes
+     * written to, but for virtio-blk it seems to be the number of bytes
+     * transferred plus the status bytes.
+     */
+    vring_push(&s->vring, req->head, len + sizeof(hdr));
+
+    s->num_reqs--;
+}
+
+static void complete_request_early(VirtIOBlockDataPlane *s, unsigned int head,
+                                   QEMUIOVector *inhdr, unsigned char status)
+{
+    struct virtio_blk_inhdr hdr = {
+        .status = status,
+    };
+
+    qemu_iovec_from_buf(inhdr, 0, &hdr, sizeof(hdr));
+    qemu_iovec_destroy(inhdr);
+    g_slice_free(QEMUIOVector, inhdr);
+
+    vring_push(&s->vring, head, sizeof(hdr));
+    notify_guest(s);
+}
+
+/* Get disk serial number */
+static void do_get_id_cmd(VirtIOBlockDataPlane *s,
+                          struct iovec *iov, unsigned int iov_cnt,
+                          unsigned int head, QEMUIOVector *inhdr)
+{
+    char id[VIRTIO_BLK_ID_BYTES];
+
+    /* Serial number not NUL-terminated when shorter than buffer */
+    strncpy(id, s->blk->serial ? s->blk->serial : "", sizeof(id));
+    iov_from_buf(iov, iov_cnt, 0, id, sizeof(id));
+    complete_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
+}
+
+static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
+                       struct iovec *iov, unsigned int iov_cnt,
+                       long long offset, unsigned int head,
+                       QEMUIOVector *inhdr)
+{
+    struct iocb *iocb;
+    QEMUIOVector qiov;
+    struct iovec *bounce_iov = NULL;
+    QEMUIOVector *read_qiov = NULL;
+
+    qemu_iovec_init_external(&qiov, iov, iov_cnt);
+    if (!bdrv_qiov_is_aligned(s->blk->conf.bs, &qiov)) {
+        void *bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov.size);
+
+        if (read) {
+            /* Need to copy back from bounce buffer on completion */
+            read_qiov = g_slice_new(QEMUIOVector);
+            qemu_iovec_init(read_qiov, iov_cnt);
+            qemu_iovec_concat_iov(read_qiov, iov, iov_cnt, 0, qiov.size);
+        } else {
+            qemu_iovec_to_buf(&qiov, 0, bounce_buffer, qiov.size);
+        }
+
+        /* Redirect I/O to aligned bounce buffer */
+        bounce_iov = g_slice_new(struct iovec);
+        bounce_iov->iov_base = bounce_buffer;
+        bounce_iov->iov_len = qiov.size;
+        iov = bounce_iov;
+        iov_cnt = 1;
+    }
+
+    iocb = ioq_rdwr(&s->ioqueue, read, iov, iov_cnt, offset);
+
+    /* Fill in virtio block metadata needed for completion */
+    VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
+    req->head = head;
+    req->inhdr = inhdr;
+    req->bounce_iov = bounce_iov;
+    req->read_qiov = read_qiov;
+    return 0;
+}
+
+static int process_request(IOQueue *ioq, struct iovec iov[],
+                           unsigned int out_num, unsigned int in_num,
+                           unsigned int head)
+{
+    VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue);
+    struct iovec *in_iov = &iov[out_num];
+    struct virtio_blk_outhdr outhdr;
+    QEMUIOVector *inhdr;
+    size_t in_size;
+
+    /* Copy in outhdr */
+    if (unlikely(iov_to_buf(iov, out_num, 0, &outhdr,
+                            sizeof(outhdr)) != sizeof(outhdr))) {
+        error_report("virtio-blk request outhdr too short");
+        return -EFAULT;
+    }
+    iov_discard_front(&iov, &out_num, sizeof(outhdr));
+
+    /* Grab inhdr for later */
+    in_size = iov_size(in_iov, in_num);
+    if (in_size < sizeof(struct virtio_blk_inhdr)) {
+        error_report("virtio_blk request inhdr too short");
+        return -EFAULT;
+    }
+    inhdr = g_slice_new(QEMUIOVector);
+    qemu_iovec_init(inhdr, 1);
+    qemu_iovec_concat_iov(inhdr, in_iov, in_num,
+            in_size - sizeof(struct virtio_blk_inhdr),
+            sizeof(struct virtio_blk_inhdr));
+    iov_discard_back(in_iov, &in_num, sizeof(struct virtio_blk_inhdr));
+
+    /* TODO Linux sets the barrier bit even when not advertised! */
+    outhdr.type &= ~VIRTIO_BLK_T_BARRIER;
+
+    switch (outhdr.type) {
+    case VIRTIO_BLK_T_IN:
+        do_rdwr_cmd(s, true, in_iov, in_num, outhdr.sector * 512, head, inhdr);
+        return 0;
+
+    case VIRTIO_BLK_T_OUT:
+        do_rdwr_cmd(s, false, iov, out_num, outhdr.sector * 512, head, inhdr);
+        return 0;
+
+    case VIRTIO_BLK_T_SCSI_CMD:
+        /* TODO support SCSI commands */
+        complete_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP);
+        return 0;
+
+    case VIRTIO_BLK_T_FLUSH:
+        /* TODO fdsync not supported by Linux AIO, do it synchronously here! */
+        if (qemu_fdatasync(s->fd) < 0) {
+            complete_request_early(s, head, inhdr, VIRTIO_BLK_S_IOERR);
+        } else {
+            complete_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
+        }
+        return 0;
+
+    case VIRTIO_BLK_T_GET_ID:
+        do_get_id_cmd(s, in_iov, in_num, head, inhdr);
+        return 0;
+
+    default:
+        error_report("virtio-blk unsupported request type %#x", outhdr.type);
+        qemu_iovec_destroy(inhdr);
+        g_slice_free(QEMUIOVector, inhdr);
+        return -EFAULT;
+    }
+}
+
+static int flush_true(EventNotifier *e)
+{
+    return true;
+}
+
+static void handle_notify(EventNotifier *e)
+{
+    VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
+                                           host_notifier);
+
+    /* There is one array of iovecs into which all new requests are extracted
+     * from the vring.  Requests are read from the vring and the translated
+     * descriptors are written to the iovecs array.  The iovecs do not have to
+     * persist across handle_notify() calls because the kernel copies the
+     * iovecs on io_submit().
+     *
+     * Handling io_submit() EAGAIN may require storing the requests across
+     * handle_notify() calls until the kernel has sufficient resources to
+     * accept more I/O.  This is not implemented yet.
+     */
+    struct iovec iovec[VRING_MAX];
+    struct iovec *end = &iovec[VRING_MAX];
+    struct iovec *iov = iovec;
+
+    /* When a request is read from the vring, the index of the first descriptor
+     * (aka head) is returned so that the completed request can be pushed onto
+     * the vring later.
+     *
+     * The number of hypervisor read-only iovecs is out_num.  The number of
+     * hypervisor write-only iovecs is in_num.
+     */
+    int head;
+    unsigned int out_num = 0, in_num = 0;
+    unsigned int num_queued;
+
+    event_notifier_test_and_clear(&s->host_notifier);
+    for (;;) {
+        /* Disable guest->host notifies to avoid unnecessary vmexits */
+        vring_disable_notification(s->vdev, &s->vring);
+
+        for (;;) {
+            head = vring_pop(s->vdev, &s->vring, iov, end, &out_num, &in_num);
+            if (head < 0) {
+                break; /* no more requests */
+            }
+
+            trace_virtio_blk_data_plane_process_request(s, out_num, in_num,
+                                                        head);
+
+            if (process_request(&s->ioqueue, iov, out_num, in_num, head) < 0) {
+                vring_set_broken(&s->vring);
+                break;
+            }
+            iov += out_num + in_num;
+        }
+
+        if (likely(head == -EAGAIN)) { /* vring emptied */
+            /* Re-enable guest->host notifies and stop processing the vring.
+             * But if the guest has snuck in more descriptors, keep processing.
+             */
+            if (vring_enable_notification(s->vdev, &s->vring)) {
+                break;
+            }
+        } else { /* head == -ENOBUFS or fatal error, iovecs[] is depleted */
+            /* Since there are no iovecs[] left, stop processing for now.  Do
+             * not re-enable guest->host notifies since the I/O completion
+             * handler knows to check for more vring descriptors anyway.
+             */
+            break;
+        }
+    }
+
+    num_queued = ioq_num_queued(&s->ioqueue);
+    if (num_queued > 0) {
+        s->num_reqs += num_queued;
+
+        int rc = ioq_submit(&s->ioqueue);
+        if (unlikely(rc < 0)) {
+            fprintf(stderr, "ioq_submit failed %d\n", rc);
+            exit(1);
+        }
+    }
+}
+
+static int flush_io(EventNotifier *e)
+{
+    VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
+                                           io_notifier);
+
+    return s->num_reqs > 0;
+}
+
+static void handle_io(EventNotifier *e)
+{
+    VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
+                                           io_notifier);
+
+    event_notifier_test_and_clear(&s->io_notifier);
+    if (ioq_run_completion(&s->ioqueue, complete_request, s) > 0) {
+        notify_guest(s);
+    }
+
+    /* If there were more requests than iovecs, the vring will not be empty yet
+     * so check again.  There should now be enough resources to process more
+     * requests.
+     */
+    if (unlikely(vring_more_avail(&s->vring))) {
+        handle_notify(&s->host_notifier);
+    }
+}
+
+static void *data_plane_thread(void *opaque)
+{
+    VirtIOBlockDataPlane *s = opaque;
+
+    do {
+        aio_poll(s->ctx, true);
+    } while (!s->stopping || s->num_reqs > 0);
+    return NULL;
+}
+
+static void start_data_plane_bh(void *opaque)
+{
+    VirtIOBlockDataPlane *s = opaque;
+
+    qemu_bh_delete(s->start_bh);
+    s->start_bh = NULL;
+    qemu_thread_create(&s->thread, data_plane_thread,
+                       s, QEMU_THREAD_JOINABLE);
+}
+
+bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
+                                  VirtIOBlockDataPlane **dataplane)
+{
+    VirtIOBlockDataPlane *s;
+    int fd;
+
+    *dataplane = NULL;
+
+    if (!blk->data_plane) {
+        return true;
+    }
+
+    if (blk->scsi) {
+        error_report("device is incompatible with x-data-plane, use scsi=off");
+        return false;
+    }
+
+    if (blk->config_wce) {
+        error_report("device is incompatible with x-data-plane, "
+                     "use config-wce=off");
+        return false;
+    }
+
+    fd = raw_get_aio_fd(blk->conf.bs);
+    if (fd < 0) {
+        error_report("drive is incompatible with x-data-plane, "
+                     "use format=raw,cache=none,aio=native");
+        return false;
+    }
+
+    s = g_new0(VirtIOBlockDataPlane, 1);
+    s->vdev = vdev;
+    s->fd = fd;
+    s->blk = blk;
+
+    /* Prevent block operations that conflict with data plane thread */
+    bdrv_set_in_use(blk->conf.bs, 1);
+
+    error_setg(&s->migration_blocker,
+            "x-data-plane does not support migration");
+    migrate_add_blocker(s->migration_blocker);
+
+    *dataplane = s;
+    return true;
+}
+
+void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
+{
+    if (!s) {
+        return;
+    }
+
+    virtio_blk_data_plane_stop(s);
+    migrate_del_blocker(s->migration_blocker);
+    error_free(s->migration_blocker);
+    bdrv_set_in_use(s->blk->conf.bs, 0);
+    g_free(s);
+}
+
+void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
+{
+    VirtQueue *vq;
+    int i;
+
+    if (s->started) {
+        return;
+    }
+
+    vq = virtio_get_queue(s->vdev, 0);
+    if (!vring_setup(&s->vring, s->vdev, 0)) {
+        return;
+    }
+
+    s->ctx = aio_context_new();
+
+    /* Set up guest notifier (irq) */
+    if (s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1,
+                                              true) != 0) {
+        fprintf(stderr, "virtio-blk failed to set guest notifier, "
+                "ensure -enable-kvm is set\n");
+        exit(1);
+    }
+    s->guest_notifier = virtio_queue_get_guest_notifier(vq);
+
+    /* Set up virtqueue notify */
+    if (s->vdev->binding->set_host_notifier(s->vdev->binding_opaque,
+                                            0, true) != 0) {
+        fprintf(stderr, "virtio-blk failed to set host notifier\n");
+        exit(1);
+    }
+    s->host_notifier = *virtio_queue_get_host_notifier(vq);
+    aio_set_event_notifier(s->ctx, &s->host_notifier, handle_notify, flush_true);
+
+    /* Set up ioqueue */
+    ioq_init(&s->ioqueue, s->fd, REQ_MAX);
+    for (i = 0; i < ARRAY_SIZE(s->requests); i++) {
+        ioq_put_iocb(&s->ioqueue, &s->requests[i].iocb);
+    }
+    s->io_notifier = *ioq_get_notifier(&s->ioqueue);
+    aio_set_event_notifier(s->ctx, &s->io_notifier, handle_io, flush_io);
+
+    s->started = true;
+    trace_virtio_blk_data_plane_start(s);
+
+    /* Kick right away to begin processing requests already in vring */
+    event_notifier_set(virtio_queue_get_host_notifier(vq));
+
+    /* Spawn thread in BH so it inherits iothread cpusets */
+    s->start_bh = qemu_bh_new(start_data_plane_bh, s);
+    qemu_bh_schedule(s->start_bh);
+}
+
+void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
+{
+    if (!s->started || s->stopping) {
+        return;
+    }
+    s->stopping = true;
+    trace_virtio_blk_data_plane_stop(s);
+
+    /* Stop thread or cancel pending thread creation BH */
+    if (s->start_bh) {
+        qemu_bh_delete(s->start_bh);
+        s->start_bh = NULL;
+    } else {
+        aio_notify(s->ctx);
+        qemu_thread_join(&s->thread);
+    }
+
+    aio_set_event_notifier(s->ctx, &s->io_notifier, NULL, NULL);
+    ioq_cleanup(&s->ioqueue);
+
+    aio_set_event_notifier(s->ctx, &s->host_notifier, NULL, NULL);
+    s->vdev->binding->set_host_notifier(s->vdev->binding_opaque, 0, false);
+
+    aio_context_unref(s->ctx);
+
+    /* Clean up guest notifier (irq) */
+    s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1, false);
+
+    vring_teardown(&s->vring);
+    s->started = false;
+    s->stopping = false;
+}
diff --git a/hw/block/dataplane/virtio-blk.h b/hw/block/dataplane/virtio-blk.h
new file mode 100644
index 0000000000..c90e99f48f
--- /dev/null
+++ b/hw/block/dataplane/virtio-blk.h
@@ -0,0 +1,29 @@
+/*
+ * Dedicated thread for virtio-blk I/O processing
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *   Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef HW_DATAPLANE_VIRTIO_BLK_H
+#define HW_DATAPLANE_VIRTIO_BLK_H
+
+#include "hw/virtio/virtio.h"
+
+typedef struct VirtIOBlockDataPlane VirtIOBlockDataPlane;
+
+bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
+                                  VirtIOBlockDataPlane **dataplane);
+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);
+
+#endif /* HW_DATAPLANE_VIRTIO_BLK_H */