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Re: [PATCH v3 1/2] vhost: Change the sequence of device start
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH v3 1/2] vhost: Change the sequence of device start |
Date: |
Sat, 5 Nov 2022 12:43:42 -0400 |
On Mon, Oct 17, 2022 at 02:44:51PM +0800, Yajun Wu wrote:
> This patch is part of adding vhost-user vhost_dev_start support. The
> motivation is to improve backend configuration speed and reduce live
> migration VM downtime.
>
> Moving the device start routines after finishing all the necessary device
> and VQ configuration, further aligning to the virtio specification for
> "device initialization sequence".
>
> Following patch will add vhost-user vhost_dev_start support.
>
> Signed-off-by: Yajun Wu <yajunw@nvidia.com>
> Acked-by: Parav Pandit <parav@nvidia.com>
>
> ---
> hw/block/vhost-user-blk.c | 18 +++++++++++-------
> hw/net/vhost_net.c | 12 ++++++------
> 2 files changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index 84902dde17..f4deb8cd5d 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -164,13 +164,6 @@ static int vhost_user_blk_start(VirtIODevice *vdev,
> Error **errp)
> goto err_guest_notifiers;
> }
>
> - ret = vhost_dev_start(&s->dev, vdev);
> - if (ret < 0) {
> - error_setg_errno(errp, -ret, "Error starting vhost");
> - goto err_guest_notifiers;
> - }
> - s->started_vu = true;
> -
> /* guest_notifier_mask/pending not used yet, so just unmask
> * everything here. virtio-pci will do the right thing by
> * enabling/disabling irqfd.
> @@ -179,9 +172,20 @@ static int vhost_user_blk_start(VirtIODevice *vdev,
> Error **errp)
> vhost_virtqueue_mask(&s->dev, vdev, i, false);
> }
>
> + s->dev.vq_index_end = s->dev.nvqs;
> + ret = vhost_dev_start(&s->dev, vdev);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Error starting vhost");
> + goto err_guest_notifiers;
> + }
> + s->started_vu = true;
> +
> return ret;
>
> err_guest_notifiers:
> + for (i = 0; i < s->dev.nvqs; i++) {
> + vhost_virtqueue_mask(&s->dev, vdev, i, true);
> + }
> k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
> err_host_notifiers:
> vhost_dev_disable_notifiers(&s->dev, vdev);
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index d28f8b974b..d6924f5e57 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -387,21 +387,21 @@ int vhost_net_start(VirtIODevice *dev, NetClientState
> *ncs,
> } else {
> peer = qemu_get_peer(ncs, n->max_queue_pairs);
> }
> - r = vhost_net_start_one(get_vhost_net(peer), dev);
> -
> - if (r < 0) {
> - goto err_start;
> - }
>
> if (peer->vring_enable) {
> /* restore vring enable state */
> r = vhost_set_vring_enable(peer, peer->vring_enable);
>
> if (r < 0) {
> - vhost_net_stop_one(get_vhost_net(peer), dev);
> goto err_start;
> }
> }
> +
> + r = vhost_net_start_one(get_vhost_net(peer), dev);
> + if (r < 0) {
> + vhost_net_stop_one(get_vhost_net(peer), dev);
Error handling broken here. Corrupts memory if triggered.
I fixed it up when applying just because of the freeze
but I won't do this generally.
> + goto err_start;
> + }
> }
>
> return 0;
> --
> 2.27.0
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