Function virtio_ethdev_negotiate_features

dpdk/drivers/net/virtio/virtio_ethdev.c:1097–1147

}

static int
virtio_ethdev_negotiate_features(struct virtio_hw *hw, uint64_t req_features)
{
	uint64_t host_features;

	/* Prepare guest_features: feature that driver wants to support */
	PMD_INIT_LOG(DEBUG, "guest_features before negotiate = %" PRIx64,
		req_features);

	/* Read device(host) feature bits */
	host_features = VIRTIO_OPS(hw)->get_features(hw);
	PMD_INIT_LOG(DEBUG, "host_features before negotiate = %" PRIx64,
		host_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;

		virtio_read_dev_config(hw,
			offsetof(struct virtio_net_config, mtu),
			&config.mtu, sizeof(config.mtu));

		if (config.mtu < RTE_ETHER_MIN_MTU)
			req_features &= ~(1ULL << VIRTIO_NET_F_MTU);
	}

	/*
	 * Negotiate features: Subset of device feature bits are written back
	 * guest feature bits.
	 */
	hw->guest_features = req_features;
	hw->guest_features = virtio_negotiate_features(hw, host_features);
	PMD_INIT_LOG(DEBUG, "features after negotiate = %" PRIx64,
		hw->guest_features);

	if (VIRTIO_OPS(hw)->features_ok(hw) < 0)
		return -1;

	if (virtio_with_feature(hw, VIRTIO_F_VERSION_1)) {
		virtio_set_status(hw, VIRTIO_CONFIG_STATUS_FEATURES_OK);

		if (!(virtio_get_status(hw) & VIRTIO_CONFIG_STATUS_FEATURES_OK)) {
			PMD_INIT_LOG(ERR, "Failed to set FEATURES_OK status!");
			return -1;
		}
	}

	hw->req_guest_features = req_features;

	return 0;
}

static void
virtio_notify_peers(struct rte_eth_dev *dev)