[UNIKRAFT PATCH v5 09/10] plat/xen/drivers/net: Add transmit operation

[Costin Lupu <costin.lupu@xxxxxxxxx>]

Whenever a packet is transmitted, the request describing it is written in the
shared ring. The packet itself is written in a page referenced by the request
and shared, as well, with the backend. At the end of each transmit operation, a
cleanup operation is performed free'ing the resources allocated for the
previously transmitted packets.

Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
Signed-off-by: Razvan Cojocaru <razvan.cojocaru93@xxxxxxxxx>
---
 plat/xen/drivers/net/netfront.c | 113 ++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)

diff --git a/plat/xen/drivers/net/netfront.c b/plat/xen/drivers/net/netfront.c
index 48b7c02f..5cae3efa 100644
--- a/plat/xen/drivers/net/netfront.c
+++ b/plat/xen/drivers/net/netfront.c
@@ -39,6 +39,7 @@
 #include <uk/alloc.h>
 #include <uk/netdev_driver.h>
 #include <xen-x86/mm.h>
+#include <xen-x86/irq.h>
 #include <xenbus/xenbus.h>
 #include "netfront.h"
 #include "netfront_xb.h"
@@ -78,6 +79,117 @@ static uint16_t get_id_from_freelist(uint16_t *freelist)
        return id;
 }
 
+static int network_tx_buf_gc(struct uk_netdev_tx_queue *txq)
+{
+       RING_IDX prod, cons;
+       netif_tx_response_t *tx_rsp;
+       uint16_t id;
+       bool more_to_do;
+       int count = 0;
+
+       do {
+               prod = txq->ring.sring->rsp_prod;
+               rmb(); /* Ensure we see responses up to 'rp'. */
+
+               for (cons = txq->ring.rsp_cons; cons != prod; cons++) {
+                       tx_rsp = RING_GET_RESPONSE(&txq->ring, cons);
+
+                       if (tx_rsp->status == NETIF_RSP_NULL)
+                               continue;
+
+                       if (tx_rsp->status == NETIF_RSP_ERROR)
+                               uk_pr_err("netdev%u: Transmission error on txq 
%u\n",
+                                       txq->netfront_dev->netdev._data->id,
+                                       txq->lqueue_id);
+
+                       id  = tx_rsp->id;
+                       UK_ASSERT(id < NET_TX_RING_SIZE);
+
+                       gnttab_end_access(txq->gref[id]);
+                       txq->gref[id] = GRANT_INVALID_REF;
+                       uk_netbuf_free_single(txq->netbuf[id]);
+
+                       add_id_to_freelist(id, txq->freelist);
+                       uk_semaphore_up(&txq->sem);
+
+                       count++;
+               }
+
+               txq->ring.rsp_cons = prod;
+
+               RING_FINAL_CHECK_FOR_RESPONSES(&txq->ring, more_to_do);
+       } while (more_to_do);
+
+       return count;
+}
+
+static int netfront_xmit(struct uk_netdev *n,
+               struct uk_netdev_tx_queue *txq,
+               struct uk_netbuf *pkt)
+{
+       struct netfront_dev *nfdev;
+       unsigned long flags;
+       uint16_t id;
+       RING_IDX req_prod;
+       netif_tx_request_t *tx_req;
+       int notify;
+       int status = 0, count;
+
+       UK_ASSERT(n != NULL);
+       UK_ASSERT(txq != NULL);
+       UK_ASSERT(pkt != NULL);
+       UK_ASSERT(pkt->len < PAGE_SIZE);
+
+       nfdev = to_netfront_dev(n);
+
+       /* get request id */
+       if (unlikely(!uk_semaphore_down_try(&txq->sem))) {
+               /* try some cleanup */
+               local_irq_save(flags);
+               count = network_tx_buf_gc(txq);
+               local_irq_restore(flags);
+               if (count == 0 || !uk_semaphore_down_try(&txq->sem))
+                       return -ENOSPC;
+       }
+       local_irq_save(flags);
+       id = get_id_from_freelist(txq->freelist);
+       local_irq_restore(flags);
+
+       /* get request */
+       req_prod = txq->ring.req_prod_pvt;
+       tx_req = RING_GET_REQUEST(&txq->ring, req_prod);
+
+       /* setup grant for buffer data */
+       txq->gref[id] = tx_req->gref =
+               gnttab_grant_access(nfdev->xendev->otherend_id,
+                       virt_to_mfn(pkt->buf), 1);
+       UK_ASSERT(tx_req->gref != GRANT_INVALID_REF);
+       txq->netbuf[id] = pkt;
+
+       tx_req->offset = 0;
+       tx_req->size = (uint16_t) pkt->len;
+       tx_req->flags = 0;
+       tx_req->id = id;
+
+       txq->ring.req_prod_pvt = req_prod + 1;
+       wmb(); /* Ensure backend sees requests */
+
+       RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&txq->ring, notify);
+       if (notify)
+               notify_remote_via_evtchn(txq->evtchn);
+
+       status |= UK_NETDEV_STATUS_SUCCESS;
+
+       /* some cleanup */
+       local_irq_save(flags);
+       count = network_tx_buf_gc(txq);
+       local_irq_restore(flags);
+
+       status |= likely(count > 0) ? UK_NETDEV_STATUS_MORE : 0x0;
+
+       return status;
+}
+
 static int netfront_rxq_enqueue(struct uk_netdev_rx_queue *rxq,
                struct uk_netbuf *netbuf)
 {
@@ -601,6 +713,7 @@ static int netfront_add_dev(struct xenbus_device *xendev)
        }
 
        /* register netdev */
+       nfdev->netdev.tx_one = netfront_xmit;
        nfdev->netdev.ops = &netfront_ops;
        rc = uk_netdev_drv_register(&nfdev->netdev, drv_allocator, DRIVER_NAME);
        if (rc < 0) {
-- 
2.20.1