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[Qemu-devel] Re: [PATCH] vhost-net: Do not set features for backend when
From: |
Jason Wang |
Subject: |
[Qemu-devel] Re: [PATCH] vhost-net: Do not set features for backend when peer was deleted |
Date: |
Wed, 27 Oct 2010 14:59:16 +0800 |
Michael S. Tsirkin writes:
> On Wed, Oct 27, 2010 at 12:43:51AM +0800, Jason Wang wrote:
> > When hot-unplug a virtio nic with vhost-net backend, guest may
> > continue to program the nic even if its peer have been deleted. We can
> > not set features at this time as vhost_net_ack_features() may still
> > try to use the tap related vhost_net structure which have been freed
> > in tap_cleanup(). And setting offload features for a deleted backend
> > is also meaningless in this situation
> >
> > Signed-off-by: Jason Wang <address@hidden>
>
> Hmm. Actually, this is not enough.
> We really must stop and cleanup vhost net.
>
But this patch just prevent the guest from programming a nic with its
vhost-net backend deleted. The vhost net was still stopped and cleaned
when the peer have been removed.
> Two issues are
> 1. vhost_net_stop needs virtio device pointer
> 2. virtio net has a vhost_started flag
>
> Two ways to fix it that I see:
> 1. add a callback in nic and invoke when peer_deleted is set
> 2. add vhost_started and virtio device pointers in vhost
>
> Path 1 seems easier ...
>
> MST
>
> > ---
> > hw/virtio-net.c | 3 +++
> > 1 files changed, 3 insertions(+), 0 deletions(-)
> >
> > diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> > index 7e1688c..68c8e48 100644
> > --- a/hw/virtio-net.c
> > +++ b/hw/virtio-net.c
> > @@ -245,6 +245,9 @@ static void virtio_net_set_features(VirtIODevice
> > *vdev, uint32_t features)
> > {
> > VirtIONet *n = to_virtio_net(vdev);
> >
> > + if (n->nic->peer_deleted)
> > + return;
> > +
> > n->mergeable_rx_bufs = !!(features & (1 << VIRTIO_NET_F_MRG_RXBUF));
> >
> > if (n->has_vnet_hdr) {
>