[dpdk-dev] [PATCH v3 2/2] net/virtio: support GUEST ANNOUNCE

[Xiao Wang]

When live migration is done, for the backup VM, either the virtio
frontend or the vhost backend needs to send out gratuitous RARP packet
to announce its new network location.

This patch enables VIRTIO_NET_F_GUEST_ANNOUNCE feature to support live
migration scenario where the vhost backend doesn't have the ability to
generate RARP packet.

Brief introduction of the work flow:
1. QEMU finishes live migration, pokes the backup VM with an interrupt.
2. Virtio interrupt handler reads out the interrupt status value, and
   realizes it needs to send out RARP packet to announce its location.
3. Pause device to stop worker thread touching the queues.
4. Inject a RARP packet into a Tx Queue.
5. Ack the interrupt via control queue.
6. Resume device to continue packet processing.

Signed-off-by: Xiao Wang <xiao.w.wang at intel.com>
---
v3:
- Remove Tx function code duplication, use a special pointer for rarp
  injection.
- Rename function generate_rarp to virtio_notify_peers, replace
  'virtnet_' with 'virtio_'.
- Add comment for state_lock.
- Typo fix and comment improvement.

v2:
- Use rte_pktmbuf_mtod directly to get eth_hdr addr.
- Fix virtio_dev_pause return value check.
---
 drivers/net/virtio/virtio_ethdev.c      | 138 +++++++++++++++++++++++++++++++-
 drivers/net/virtio/virtio_ethdev.h      |   1 +
 drivers/net/virtio/virtio_pci.h         |   7 ++
 drivers/net/virtio/virtio_rxtx.c        |   2 +-
 drivers/net/virtio/virtio_rxtx_simple.c |   2 +-
 drivers/net/virtio/virtqueue.h          |  11 +++
 6 files changed, 157 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index ac73950..80bad52 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -48,6 +48,8 @@
 #include <rte_pci.h>
 #include <rte_bus_pci.h>
 #include <rte_ether.h>
+#include <rte_ip.h>
+#include <rte_arp.h>
 #include <rte_common.h>
 #include <rte_errno.h>
 #include <rte_cpuflags.h>
@@ -55,6 +57,7 @@
 #include <rte_memory.h>
 #include <rte_eal.h>
 #include <rte_dev.h>
+#include <rte_cycles.h>
 
 #include "virtio_ethdev.h"
 #include "virtio_pci.h"
@@ -106,6 +109,13 @@ static int virtio_dev_queue_stats_mapping_set(
 	uint8_t stat_idx,
 	uint8_t is_rx);
 
+static int make_rarp_packet(struct rte_mbuf *rarp_mbuf,
+		const struct ether_addr *mac);
+static int virtio_dev_pause(struct rte_eth_dev *dev);
+static void virtio_dev_resume(struct rte_eth_dev *dev);
+static void virtio_notify_peers(struct rte_eth_dev *dev);
+static void virtio_ack_link_announce(struct rte_eth_dev *dev);
+
 /*
  * The set of PCI devices this driver supports
  */
@@ -1249,9 +1259,116 @@ static int virtio_dev_xstats_get_names(struct rte_eth_dev *dev,
 	return 0;
 }
 
+#define RARP_PKT_SIZE	64
+static int
+make_rarp_packet(struct rte_mbuf *rarp_mbuf, const struct ether_addr *mac)
+{
+	struct ether_hdr *eth_hdr;
+	struct arp_hdr  *rarp;
+
+	if (rarp_mbuf->buf_len < RARP_PKT_SIZE) {
+		PMD_DRV_LOG(ERR, "mbuf size too small %u (< %d)",
+				rarp_mbuf->buf_len, RARP_PKT_SIZE);
+		return -1;
+	}
+
+	/* Ethernet header. */
+	eth_hdr = rte_pktmbuf_mtod(rarp_mbuf, struct ether_hdr *);
+	memset(eth_hdr->d_addr.addr_bytes, 0xff, ETHER_ADDR_LEN);
+	ether_addr_copy(mac, &eth_hdr->s_addr);
+	eth_hdr->ether_type = htons(ETHER_TYPE_RARP);
+
+	/* RARP header. */
+	rarp = (struct arp_hdr *)(eth_hdr + 1);
+	rarp->arp_hrd = htons(ARP_HRD_ETHER);
+	rarp->arp_pro = htons(ETHER_TYPE_IPv4);
+	rarp->arp_hln = ETHER_ADDR_LEN;
+	rarp->arp_pln = 4;
+	rarp->arp_op  = htons(ARP_OP_REVREQUEST);
+
+	ether_addr_copy(mac, &rarp->arp_data.arp_sha);
+	ether_addr_copy(mac, &rarp->arp_data.arp_tha);
+	memset(&rarp->arp_data.arp_sip, 0x00, 4);
+	memset(&rarp->arp_data.arp_tip, 0x00, 4);
+
+	rarp_mbuf->data_len = RARP_PKT_SIZE;
+	rarp_mbuf->pkt_len = RARP_PKT_SIZE;
+
+	return 0;
+}
+
+static int
+virtio_dev_pause(struct rte_eth_dev *dev)
+{
+	struct virtio_hw *hw = dev->data->dev_private;
+
+	if (hw->started == 0)
+		return -1;
+	hw->started = 0;
+	/*
+	 * Prevent the worker thread from touching queues to avoid contention,
+	 * 1 ms should be enough for the ongoing Tx function to finish.
+	 */
+	rte_delay_ms(1);
+	return 0;
+}
+
+static void
+virtio_dev_resume(struct rte_eth_dev *dev)
+{
+	struct virtio_hw *hw = dev->data->dev_private;
+
+	hw->started = 1;
+}
+
+static void
+virtio_notify_peers(struct rte_eth_dev *dev)
+{
+	struct virtio_hw *hw = dev->data->dev_private;
+	struct virtnet_tx *txvq = dev->data->tx_queues[0];
+	struct virtnet_rx *rxvq = dev->data->rx_queues[0];
+
+	hw->rarp_buf[0] = rte_mbuf_raw_alloc(rxvq->mpool);
+	if (hw->rarp_buf[0] == NULL) {
+		PMD_DRV_LOG(ERR, "first mbuf allocate failed");
+		return;
+	}
+
+	if (make_rarp_packet(hw->rarp_buf[0],
+				(struct ether_addr *)hw->mac_addr)) {
+		rte_pktmbuf_free(hw->rarp_buf[0]);
+		return;
+	}
+
+	/* If virtio port just stopped, no need to send RARP */
+	if (virtio_dev_pause(dev) < 0) {
+		rte_pktmbuf_free(hw->rarp_buf[0]);
+		return;
+	}
+
+	dev->tx_pkt_burst(txvq, hw->rarp_buf, 1);
+	/* Recover the stored hw status to let worker thread continue */
+	virtio_dev_resume(dev);
+}
+
+static void
+virtio_ack_link_announce(struct rte_eth_dev *dev)
+{
+	struct virtio_hw *hw = dev->data->dev_private;
+	struct virtio_pmd_ctrl ctrl;
+	int len;
+
+	ctrl.hdr.class = VIRTIO_NET_CTRL_ANNOUNCE;
+	ctrl.hdr.cmd = VIRTIO_NET_CTRL_ANNOUNCE_ACK;
+	len = 0;
+
+	virtio_send_command(hw->cvq, &ctrl, &len, 0);
+}
+
 /*
- * Process Virtio Config changed interrupt and call the callback
- * if link state changed.
+ * Process virtio config changed interrupt. Call the callback
+ * if link state changed, generate gratuitous RARP packet if
+ * the status indicates an ANNOUNCE.
  */
 void
 virtio_interrupt_handler(void *param)
@@ -1274,6 +1391,12 @@ static int virtio_dev_xstats_get_names(struct rte_eth_dev *dev,
 						      NULL, NULL);
 	}
 
+	if (isr & VIRTIO_NET_S_ANNOUNCE) {
+		rte_spinlock_lock(&hw->state_lock);
+		virtio_notify_peers(dev);
+		virtio_ack_link_announce(dev);
+		rte_spinlock_unlock(&hw->state_lock);
+	}
 }
 
 /* set rx and tx handlers according to what is supported */
@@ -1786,6 +1909,8 @@ static int eth_virtio_pci_remove(struct rte_pci_device *pci_dev)
 			return -EBUSY;
 		}
 
+	rte_spinlock_init(&hw->state_lock);
+
 	hw->use_simple_rx = 1;
 	hw->use_simple_tx = 1;
 
@@ -1892,6 +2017,12 @@ static int eth_virtio_pci_remove(struct rte_pci_device *pci_dev)
 	/* Initialize Link state */
 	virtio_dev_link_update(dev, 0);
 
+	hw->rarp_buf = rte_zmalloc("rarp_buf", sizeof(struct rte_mbuf *), 0);
+	if (!hw->rarp_buf) {
+		PMD_INIT_LOG(ERR, "Failed to allocate rarp pointer");
+		return -ENOMEM;
+	}
+
 	return 0;
 }
 
@@ -1952,12 +2083,15 @@ static void virtio_dev_free_mbufs(struct rte_eth_dev *dev)
 
 	PMD_INIT_LOG(DEBUG, "stop");
 
+	rte_spinlock_lock(&hw->state_lock);
 	if (intr_conf->lsc || intr_conf->rxq)
 		virtio_intr_disable(dev);
 
 	hw->started = 0;
 	memset(&link, 0, sizeof(link));
 	virtio_dev_atomic_write_link_status(dev, &link);
+	rte_free(hw->rarp_buf);
+	rte_spinlock_unlock(&hw->state_lock);
 }
 
 static int
diff --git a/drivers/net/virtio/virtio_ethdev.h b/drivers/net/virtio/virtio_ethdev.h
index 2039bc5..58faa22 100644
--- a/drivers/net/virtio/virtio_ethdev.h
+++ b/drivers/net/virtio/virtio_ethdev.h
@@ -67,6 +67,7 @@
 	 1u << VIRTIO_NET_F_HOST_TSO6	  |	\
 	 1u << VIRTIO_NET_F_MRG_RXBUF	  |	\
 	 1u << VIRTIO_NET_F_MTU	| \
+	 1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE  | \
 	 1u << VIRTIO_RING_F_INDIRECT_DESC |    \
 	 1ULL << VIRTIO_F_VERSION_1       |	\
 	 1ULL << VIRTIO_F_IOMMU_PLATFORM)
diff --git a/drivers/net/virtio/virtio_pci.h b/drivers/net/virtio/virtio_pci.h
index 3c5ce66..7bd6c50 100644
--- a/drivers/net/virtio/virtio_pci.h
+++ b/drivers/net/virtio/virtio_pci.h
@@ -270,6 +270,13 @@ struct virtio_hw {
 	struct virtio_pci_common_cfg *common_cfg;
 	struct virtio_net_config *dev_cfg;
 	void	    *virtio_user_dev;
+	/*
+	 * App management thread and virtio interrupt handler thread
+	 * both can change the 'started' flag, this lock is meant to
+	 * avoid such a contention.
+	 */
+	rte_spinlock_t state_lock;
+	struct rte_mbuf **rarp_buf;
 
 	struct virtqueue **vqs;
 };
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 6a24fde..6bae8a6 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -1017,7 +1017,7 @@
 	uint16_t nb_used, nb_tx = 0;
 	int error;
 
-	if (unlikely(hw->started == 0))
+	if (unlikely(hw->started == 0) && tx_pkts != hw->rarp_buf)
 		return nb_tx;
 
 	if (unlikely(nb_pkts < 1))
diff --git a/drivers/net/virtio/virtio_rxtx_simple.c b/drivers/net/virtio/virtio_rxtx_simple.c
index b5bc1c4..a04f20e 100644
--- a/drivers/net/virtio/virtio_rxtx_simple.c
+++ b/drivers/net/virtio/virtio_rxtx_simple.c
@@ -99,7 +99,7 @@ int __attribute__((cold))
 	uint16_t desc_idx_max = (vq->vq_nentries >> 1) - 1;
 	uint16_t nb_tx = 0;
 
-	if (unlikely(hw->started == 0))
+	if (unlikely(hw->started == 0) && tx_pkts != hw->rarp_buf)
 		return nb_tx;
 
 	nb_used = VIRTQUEUE_NUSED(vq);
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 2305d91..d9045e1 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -158,6 +158,17 @@ struct virtio_net_ctrl_mac {
 #define VIRTIO_NET_CTRL_VLAN_ADD 0
 #define VIRTIO_NET_CTRL_VLAN_DEL 1
 
+/*
+ * Control link announce acknowledgement
+ *
+ * The command VIRTIO_NET_CTRL_ANNOUNCE_ACK is used to indicate that
+ * driver has recevied the notification; device would clear the
+ * VIRTIO_NET_S_ANNOUNCE bit in the status field after it receives
+ * this command.
+ */
+#define VIRTIO_NET_CTRL_ANNOUNCE     3
+#define VIRTIO_NET_CTRL_ANNOUNCE_ACK 0
+
 struct virtio_net_ctrl_hdr {
 	uint8_t class;
 	uint8_t cmd;
-- 
1.8.3.1