Re: [Qemu-devel] [untested PATCH] virtio: fix vhost handling

[Stefan Hajnoczi]

On Fri, Aug 3, 2012 at 5:16 PM, Paolo Bonzini <address@hidden> wrote:
> Commit b1f416aa8d870fab71030abc9401cfc77b948e8e breaks vhost_net
> because it always registers the virtio_pci_host_notifier_read() handler
> function on the ioeventfd, even when vhost_net.ko is using the ioeventfd.
> The result is both QEMU and vhost_net.ko polling on the same eventfd
> and the virtio_net.ko guest driver seeing inconsistent results:
>
>   # ifconfig eth0 192.168.0.1 netmask 255.255.255.0
>   virtio_net virtio0: output:id 0 is not a head!
>
> To fix this, proceed the same as we do for irqfd: add a parameter to
> virtio_queue_set_host_notifier_fd_handler and in that case only set
> the notifier, not the handler
>
> Cc: Stefan Hajnoczi <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>         Interesting, I tested vhost (or thought so).  Can you try this
>         patch instead?

Does this really make the code better than just reverting the patch?

Tested-by: Stefan Hajnoczi <address@hidden>

>
>  hw/virtio-pci.c |   14 +++++++-------
>  hw/virtio.c     |    7 +++++--
>  hw/virtio.h     |    3 ++-
>  3 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 3ab9747..6133626 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -160,7 +160,7 @@ static int virtio_pci_load_queue(void * opaque, int n, 
> QEMUFile *f)
>  }
>
>  static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
> -                                                 int n, bool assign)
> +                                                 int n, bool assign, bool 
> with_vhost)

I don't like this name because virtio-blk-data-plane also wants to use
the ioeventfd.  I suggest we call it use_handler (note logic is
reversed from with_vhost).

Stefan