18.12.2018, 17:16, "Yongji Xie" <elohi...@gmail.com>:
> On Tue, 18 Dec 2018 at 20:30, Yury Kotov <yury-ko...@yandex-team.ru> wrote:
>> + wrfsh@
>>
>> Hi,
>>
>> 18.12.2018, 13:01, "elohi...@gmail.com" <elohi...@gmail.com>:
>> > From: Xie Yongji <xieyon...@baidu.com>
>> >
>> > Since we now support the message VHOST_USER_GET_SHM_SIZE
>> > and VHOST_USER_SET_SHM_FD. The backend is able to restart
>> > safely because it can record inflight I/O in shared memory.
>> > This patch allows qemu to reconnect the backend after
>> > connection closed.
>> >
>> > Signed-off-by: Xie Yongji <xieyon...@baidu.com>
>> > Signed-off-by: Ni Xun <ni...@baidu.com>
>> > Signed-off-by: Zhang Yu <zhangy...@baidu.com>
>> > ---
>> > hw/block/vhost-user-blk.c | 183 ++++++++++++++++++++++++-----
>> > include/hw/virtio/vhost-user-blk.h | 4 +
>> > 2 files changed, 160 insertions(+), 27 deletions(-)
>> >
>> > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
>> > index 27028cf996..80f2e2d765 100644
>> > --- a/hw/block/vhost-user-blk.c
>> > +++ b/hw/block/vhost-user-blk.c
>> > @@ -101,7 +101,7 @@ const VhostDevConfigOps blk_ops = {
>> > .vhost_dev_config_notifier = vhost_user_blk_handle_config_change,
>> > };
>> >
>> > -static void vhost_user_blk_start(VirtIODevice *vdev)
>> > +static int vhost_user_blk_start(VirtIODevice *vdev)
>> > {
>> > VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
>> > @@ -110,13 +110,13 @@ static void vhost_user_blk_start(VirtIODevice *vdev)
>> >
>> > if (!k->set_guest_notifiers) {
>> > error_report("binding does not support guest notifiers");
>> > - return;
>> > + return -ENOSYS;
>> > }
>> >
>> > ret = vhost_dev_enable_notifiers(&s->dev, vdev);
>> > if (ret < 0) {
>> > error_report("Error enabling host notifiers: %d", -ret);
>> > - return;
>> > + return ret;
>> > }
>> >
>> > ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, true);
>> > @@ -147,12 +147,13 @@ static void vhost_user_blk_start(VirtIODevice *vdev)
>> > vhost_virtqueue_mask(&s->dev, vdev, i, false);
>> > }
>> >
>> > - return;
>> > + return ret;
>> >
>> > err_guest_notifiers:
>> > k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
>> > err_host_notifiers:
>> > vhost_dev_disable_notifiers(&s->dev, vdev);
>> > + return ret;
>> > }
>> >
>> > static void vhost_user_blk_stop(VirtIODevice *vdev)
>> > @@ -171,7 +172,6 @@ static void vhost_user_blk_stop(VirtIODevice *vdev)
>> > ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
>> > if (ret < 0) {
>> > error_report("vhost guest notifier cleanup failed: %d", ret);
>> > - return;
>> > }
>> >
>> > vhost_dev_disable_notifiers(&s->dev, vdev);
>> > @@ -181,21 +181,43 @@ static void vhost_user_blk_set_status(VirtIODevice
>> *vdev, uint8_t status)
>> > {
>> > VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > bool should_start = status & VIRTIO_CONFIG_S_DRIVER_OK;
>> > + int ret;
>> >
>> > if (!vdev->vm_running) {
>> > should_start = false;
>> > }
>> >
>> > - if (s->dev.started == should_start) {
>> > + if (s->should_start == should_start) {
>> > + return;
>> > + }
>> > +
>> > + if (!s->connected || s->dev.started == should_start) {
>> > + s->should_start = should_start;
>> > return;
>> > }
>> >
>> > if (should_start) {
>> > - vhost_user_blk_start(vdev);
>> > + s->should_start = true;
>> > + /*
>> > + * make sure vhost_user_blk_handle_output() ignores fake
>> > + * guest kick by vhost_dev_enable_notifiers()
>> > + */
>> > + barrier();
>> > + ret = vhost_user_blk_start(vdev);
>> > + if (ret < 0) {
>> > + error_report("vhost-user-blk: vhost start failed: %s",
>> > + strerror(-ret));
>> > + qemu_chr_fe_disconnect(&s->chardev);
>> > + }
>> > } else {
>> > vhost_user_blk_stop(vdev);
>> > + /*
>> > + * make sure vhost_user_blk_handle_output() ignore fake
>> > + * guest kick by vhost_dev_disable_notifiers()
>> > + */
>> > + barrier();
>> > + s->should_start = false;
>> > }
>> > -
>> > }
>> >
>> > static uint64_t vhost_user_blk_get_features(VirtIODevice *vdev,
>> > @@ -225,13 +247,22 @@ static uint64_t
>> vhost_user_blk_get_features(VirtIODevice *vdev,
>> > static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue
>> *vq)
>> > {
>> > VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > - int i;
>> > + int i, ret;
>> >
>> > if (!(virtio_host_has_feature(vdev, VIRTIO_F_VERSION_1) &&
>> > !virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1))) {
>> > return;
>> > }
>> >
>> > + if (s->should_start) {
>> > + return;
>> > + }
>> > + s->should_start = true;
>> > +
>> > + if (!s->connected) {
>> > + return;
>> > + }
>> > +
>> > if (s->dev.started) {
>> > return;
>> > }
>> > @@ -239,7 +270,13 @@ static void
>> vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>> > /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
>> > * vhost here instead of waiting for .set_status().
>> > */
>> > - vhost_user_blk_start(vdev);
>> > + ret = vhost_user_blk_start(vdev);
>> > + if (ret < 0) {
>> > + error_report("vhost-user-blk: vhost start failed: %s",
>> > + strerror(-ret));
>> > + qemu_chr_fe_disconnect(&s->chardev);
>> > + return;
>> > + }
>> >
>> > /* Kick right away to begin processing requests already in vring */
>> > for (i = 0; i < s->dev.nvqs; i++) {
>> > @@ -259,12 +296,105 @@ static void vhost_user_blk_reset(VirtIODevice
>> *vdev)
>> > vhost_dev_reset_shm(s->shm);
>> > }
>> >
>> > +static int vhost_user_blk_connect(DeviceState *dev)
>> > +{
>> > + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>> > + VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > + int ret = 0;
>> > +
>> > + if (s->connected) {
>> > + return 0;
>> > + }
>> > + s->connected = true;
>> > +
>> > + s->dev.nvqs = s->num_queues;
>> > + s->dev.vqs = s->vqs;
>> > + s->dev.vq_index = 0;
>> > + s->dev.backend_features = 0;
>> > +
>> > + vhost_dev_set_config_notifier(&s->dev, &blk_ops);
>> > +
>> > + ret = vhost_dev_init(&s->dev, s->vhost_user, VHOST_BACKEND_TYPE_USER,
>> 0);
>> > + if (ret < 0) {
>> > + error_report("vhost-user-blk: vhost initialization failed: %s",
>> > + strerror(-ret));
>> > + return ret;
>> > + }
>> > +
>> > + /* restore vhost state */
>> > + if (s->should_start) {
>> > + ret = vhost_user_blk_start(vdev);
>> > + if (ret < 0) {
>> > + error_report("vhost-user-blk: vhost start failed: %s",
>> > + strerror(-ret));
>> > + return ret;
>> > + }
>> > + }
>> > +
>> > + return 0;
>> > +}
>> > +
>> > +static void vhost_user_blk_disconnect(DeviceState *dev)
>> > +{
>> > + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>> > + VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > +
>> > + if (!s->connected) {
>> > + return;
>> > + }
>> > + s->connected = false;
>> > +
>> > + if (s->dev.started) {
>> > + vhost_user_blk_stop(vdev);
>> > + }
>> > +
>> > + vhost_dev_cleanup(&s->dev);
>> > +}
>> > +
>> > +static gboolean vhost_user_blk_watch(GIOChannel *chan, GIOCondition cond,
>> > + void *opaque)
>> > +{
>> > + DeviceState *dev = opaque;
>> > + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>> > + VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > +
>> > + qemu_chr_fe_disconnect(&s->chardev);
>> > +
>> > + return true;
>> > +}
>> > +
>> > +static void vhost_user_blk_event(void *opaque, int event)
>> > +{
>> > + DeviceState *dev = opaque;
>> > + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>> > + VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > +
>> > + switch (event) {
>> > + case CHR_EVENT_OPENED:
>> > + if (vhost_user_blk_connect(dev) < 0) {
>> > + qemu_chr_fe_disconnect(&s->chardev);
>> > + return;
>> > + }
>> > + s->watch = qemu_chr_fe_add_watch(&s->chardev, G_IO_HUP,
>> > + vhost_user_blk_watch, dev);
>> > + break;
>> > + case CHR_EVENT_CLOSED:
>> > + vhost_user_blk_disconnect(dev);
>> > + if (s->watch) {
>> > + g_source_remove(s->watch);
>> > + s->watch = 0;
>> > + }
>> > + break;
>> > + }
>> > +}
>> > +
>> > static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
>> > {
>> > VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>> > VHostUserBlk *s = VHOST_USER_BLK(vdev);
>> > VhostUserState *user;
>> > int i, ret;
>> > + Error *err = NULL;
>> >
>> > if (!s->chardev.chr) {
>> > error_setg(errp, "vhost-user-blk: chardev is mandatory");
>> > @@ -299,23 +429,21 @@ static void
>> vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
>> > }
>> >
>> > s->shm = g_new0(struct vhost_shm, 1);
>> > -
>> > - s->dev.nvqs = s->num_queues;
>> > - s->dev.vqs = g_new(struct vhost_virtqueue, s->dev.nvqs);
>> > - s->dev.vq_index = 0;
>> > - s->dev.backend_features = 0;
>> > -
>> > - vhost_dev_set_config_notifier(&s->dev, &blk_ops);
>> > -
>> > - ret = vhost_dev_init(&s->dev, s->vhost_user, VHOST_BACKEND_TYPE_USER,
>> 0);
>> > - if (ret < 0) {
>> > - error_setg(errp, "vhost-user-blk: vhost initialization failed: %s",
>> > - strerror(-ret));
>> > - goto virtio_err;
>> > + s->vqs = g_new(struct vhost_virtqueue, s->num_queues);
>> > + s->watch = 0;
>> > + s->should_start = false;
>> > + s->connected = false;
>> > +
>> > + while (qemu_chr_fe_wait_connected(&s->chardev, &err) < 0) {
>> > + error_report_err(err);
>> > + err = NULL;
>> > + sleep(1);
>> > }
>>
>> After the reconnect loop we have some function calls to vhost backend:
>> * qemu_chr_fe_set_handlers implicit calls vhost_dev_init
>> * vhost_dev_get_config
>> * vhost_dev_init_shm
>>
>> If vhost backend will restart during their execution the initialzation will
>> be
>> failed. What do you think? May be we can call these functions inside of
>> the reconnect loop to fix it?
>
> qemu_chr_fe_wait_connected() should be called only when we are in
> disconnected state. Otherwise, it will be conflicted with reconnect
> thread.
>
Reconnect thread is started by reconnet timer callback from the main loop but
vhost_user_blk_device_realize is also runs in the main loop, so we don't a race
in this case I think.
Regards,
Yury
