On Wed, 19 Nov 2014 15:21:29 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:
> This patch validates feature dependencies during probe and fail the probing
> if a dependency is missed. This fixes the issues of hitting BUG()
> when qemu fails to advertise features correctly. One example is booting
> guest with ctrl_vq=off through qemu.
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
> Cc: Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> Changes from V1:
> - Drop VIRTIO_NET_F_*_UFO from the checklist, since it was disabled
> ---
> drivers/net/virtio_net.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 91 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ec2a8b4..b16a761 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1673,6 +1673,93 @@ static const struct attribute_group virtio_net_mrg_rx_group = {
> };
> #endif
>
> +static int virtnet_validate_features(struct virtio_device *dev,
> + unsigned int *table,
> + int table_size,
> + unsigned int feature)
> +{
> + int i;
> +
> + if (!virtio_has_feature(dev, feature)) {
Do an early return, get rid of one indentation level?
> + for (i = 0; i < table_size; i++) {
> + unsigned int f = table[i];
> +
> + if (virtio_has_feature(dev, f)) {
> + dev_err(&dev->dev,
> + "buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x was not",
s/hyperviser/hypervisor/ (also below)
> + f, feature);
> + return -EINVAL;
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> +static int virtnet_check_features(struct virtio_device *dev)
> +{
> + unsigned int features_for_ctrl_vq[] = {
> + VIRTIO_NET_F_CTRL_RX,
> + VIRTIO_NET_F_CTRL_VLAN,
> + VIRTIO_NET_F_GUEST_ANNOUNCE,
> + VIRTIO_NET_F_MQ,
> + VIRTIO_NET_F_CTRL_MAC_ADDR
> + };
> + unsigned int features_for_guest_csum[] = {
> + VIRTIO_NET_F_GUEST_TSO4,
> + VIRTIO_NET_F_GUEST_TSO6,
> + VIRTIO_NET_F_GUEST_ECN,
> + };
> + unsigned int features_for_host_csum[] = {
> + VIRTIO_NET_F_HOST_TSO4,
> + VIRTIO_NET_F_HOST_TSO6,
> + VIRTIO_NET_F_HOST_ECN,
> + };
I'm wondering whether it would be easier to read if you listed all
prereqs per feature instead of all features that depend on a feature?
It would still be hard to express the v4/v6 or conditions below in
tables, though.
Or call the arrays features_depending_on_foo?
> + int err;
> +
> + err = virtnet_validate_features(dev, features_for_ctrl_vq,
> + ARRAY_SIZE(features_for_ctrl_vq),
> + VIRTIO_NET_F_CTRL_VQ);
> + if (err)
> + return err;
If you already print a message that a user may use to fix their
hypervisor (or bug someone about it), would it make sense to check all
dependencies and print a full list of everything that is broken in the
advertised feature bits? I usually hate it if I fix one thing only to
hit the next bug when the program could have already told me about
everything I need to fix :)
> +
> + err = virtnet_validate_features(dev, features_for_guest_csum,
> + ARRAY_SIZE(features_for_guest_csum),
> + VIRTIO_NET_F_GUEST_CSUM);
> + if (err)
> + return err;
> +
> + err = virtnet_validate_features(dev, features_for_host_csum,
> + ARRAY_SIZE(features_for_host_csum),
> + VIRTIO_NET_F_CSUM);
> + if (err)
> + return err;
> +
> + if (virtio_has_feature(dev, VIRTIO_NET_F_GUEST_ECN) &&
> + (!virtio_has_feature(dev, VIRTIO_NET_F_GUEST_TSO4) ||
> + !virtio_has_feature(dev, VIRTIO_NET_F_GUEST_TSO6))) {
> + dev_err(&dev->dev,
> + "buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x or 0x%x was not",
> + VIRTIO_NET_F_GUEST_ECN,
> + VIRTIO_NET_F_GUEST_TSO4,
> + VIRTIO_NET_F_GUEST_TSO6);
> + return -EINVAL;
> + }
> +
> + if (virtio_has_feature(dev, VIRTIO_NET_F_HOST_ECN) &&
> + (!virtio_has_feature(dev, VIRTIO_NET_F_HOST_TSO4) ||
> + !virtio_has_feature(dev, VIRTIO_NET_F_HOST_TSO6))) {
> + dev_err(&dev->dev,
> + "buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x or 0x%x was not",
"Hypervisor bug: advertised feature <foo> but not <bar> or <baz>"
?
> + VIRTIO_NET_F_HOST_ECN,
> + VIRTIO_NET_F_HOST_TSO4,
> + VIRTIO_NET_F_HOST_TSO6);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> static int virtnet_probe(struct virtio_device *vdev)
> {
> int i, err;
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