On Thu, 13 Nov 2014 13:52:54 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:
> This patch tries to detect the possible buggy features advertised by host
> and fix them. One example is booting virtio-net with only ctrl_vq disabled,
> qemu may still advertise many features which depends on it. This will
> trigger several BUG()s in virtnet_send_command().
>
> This patch utilizes the fix_features() method, and disables all features that
> depends on ctrl_vq if it was not advertised.
>
> This fixes the crash when booting with ctrl_vq=off.
That's a qemu device property, right? Might want to mention that, as
this line sounds like it is a kernel parameter.
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> Changes from V1:
> - fix the cut-and-paste error
> ---
> drivers/net/virtio_net.c | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ec2a8b4..6ce125e 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1948,6 +1948,40 @@ static int virtnet_restore(struct virtio_device *vdev)
> }
> #endif
>
> +static void virtnet_fix_features(struct virtio_device *dev)
> +{
> + if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
> + if (virtio_has_feature(dev, VIRTIO_NET_F_CTRL_RX)) {
> + pr_warning("Disable VIRTIO_NET_F_CTRL_RX since host "
> + "does not advertise VIRTIO_NET_F_CTRL_VQ");
> + virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_RX);
> + }
You should probably use dev_warn() or so, so that the user can figure
out which device the message is for. And perhaps add "buggy hypervisor"
to the message to make clear that it's not a guest problem.
I also like the suggestion to use a dependency array.
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