On Fri, Apr 07, 2017 at 07:57:40AM +0000, Jianfeng Tan wrote:
> After the introduction of vhost MTU, VIRTIO_NET_F_MTU is enabled
> by default. However, virtio-user vtpci does not support to get
> MTU from device yet, i.e., vtpci_read_dev_config(MTU) fails.
> Plus, struct virtio_net_config is defined as a uninitialized
> variable, and could be different values in
> virtio_negotiate_features() and virtio_init_device().
>
> In some cases, it passes the check in virtio_negotiate_features()
> but fails the check in virtio_init_device(). As a result,
> virtio-user canno be initialized.
>
> To fix it, (1) accessing uninitialized variable is not a good
> practice, so initialize it as zero; (2) explicitly disable MTU
> feature in virtio-user.
>
> Fixes: 49d26d9e3f47 ("net/virtio: support MTU feature")
> Cc: Maxime Coquelin <maxime.coque...@redhat.com>
> Cc: Yuanhan Liu <yuanhan....@linux.intel.com>
>
> Signed-off-by: Jianfeng Tan <jianfeng....@intel.com>
> ---
> drivers/net/virtio/virtio_ethdev.c | 4 ++--
> drivers/net/virtio/virtio_user/virtio_user_dev.c | 6 ++++++
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_ethdev.c
> b/drivers/net/virtio/virtio_ethdev.c
> index 78cb3e8..4c43784 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -1163,7 +1163,7 @@ virtio_negotiate_features(struct virtio_hw *hw,
> uint64_t req_features)
>
> /* If supported, ensure MTU value is valid before acknowledging it. */
> if (host_features & req_features & (1ULL << VIRTIO_NET_F_MTU)) {
> - struct virtio_net_config config;
> + struct virtio_net_config config = {0};
virtio-user does not support the MTU feature, this patch should not be
reached. The virtio-user feature negotiation should be broken.
--yliu
>
> vtpci_read_dev_config(hw,
> offsetof(struct virtio_net_config, mtu),
> @@ -1332,7 +1332,7 @@ virtio_init_device(struct rte_eth_dev *eth_dev,
> uint64_t req_features)
> {
> struct virtio_hw *hw = eth_dev->data->dev_private;
> struct virtio_net_config *config;
> - struct virtio_net_config local_config;
> + struct virtio_net_config local_config = {0};
> struct rte_pci_device *pci_dev = NULL;
> int ret;
>
> diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> index 6871cd4..529b3d7 100644
> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> @@ -362,6 +362,12 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char
> *path, int queues,
> /* The backend will not report this feature, we add it explicitly */
> dev->device_features |= (1ull << VIRTIO_NET_F_STATUS);
>
> + /* TODO: VIRTIO_NET_F_MTU is for QEMU to advertise MTU to both frontend
> + * and backend driver. For virtio-user, disable it for now, until we
> + * have a parameter to specify the MTU.
> + */
> + dev->device_features &= ~(1ull << VIRTIO_NET_F_MTU);
> +
> return 0;
> }
>
> --
> 2.7.4
