On Fri, Feb 2, 2024 at 8:24 PM Yunsheng Lin [off-list ref] wrote:

On 2024/2/2 12:05, Jason Wang wrote:

quoted

On Tue, Jan 30, 2024 at 7:38 PM Yunsheng Lin [off-list ref] wrote:

quoted

introduce vhost_net_test basing on virtio_test to test
vhost_net changing in the kernel.

Let's describe what kind of test is being done and how it is done here.

How about something like below:

This patch introduces testing for both vhost_net tx and rx.
Steps for vhost_net tx testing:
1. Prepare a out buf
2. Kick the vhost_net to do tx processing
3. Do the receiving in the tun side
4. verify the data received by tun is correct

Steps for vhost_net rx testing::
1. Prepare a in buf
2. Do the sending in the tun side
3. Kick the vhost_net to do rx processing
4. verify the data received by vhost_net is correct

It looks like some important details were lost, e.g the logic for batching etc.

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+
+static int tun_alloc(struct vdev_info *dev)
+{
+       struct ifreq ifr;
+       int len = HDR_LEN;

Any reason you can't just use the virtio_net uapi?

I didn't find a macro for that in include/uapi/linux/virtio_net.h.

Did you mean using something like below?
sizeof(struct virtio_net_hdr_mrg_rxbuf)

Yes.

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+       int fd, e;
+
+       fd = open("/dev/net/tun", O_RDWR);
+       if (fd < 0) {
+               perror("Cannot open /dev/net/tun");
+               return fd;
+       }
+
+       memset(&ifr, 0, sizeof(ifr));
+
+       ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
+       snprintf(ifr.ifr_name, IFNAMSIZ, "tun_%d", getpid());
+
+       e = ioctl(fd, TUNSETIFF, &ifr);
+       if (e < 0) {
+               perror("ioctl[TUNSETIFF]");
+               close(fd);
+               return e;
+       }
+
+       e = ioctl(fd, TUNSETVNETHDRSZ, &len);
+       if (e < 0) {
+               perror("ioctl[TUNSETVNETHDRSZ]");
+               close(fd);
+               return e;
+       }
+
+       e = ioctl(fd, SIOCGIFHWADDR, &ifr);
+       if (e < 0) {
+               perror("ioctl[SIOCGIFHWADDR]");
+               close(fd);
+               return e;
+       }
+
+       memcpy(dev->mac, &ifr.ifr_hwaddr.sa_data, ETHER_ADDR_LEN);
+       return fd;
+}
+
+static void vdev_create_socket(struct vdev_info *dev)
+{
+       struct ifreq ifr;
+
+       dev->sock = socket(AF_PACKET, SOCK_RAW, htons(TEST_PTYPE));
+       assert(dev->sock != -1);
+
+       snprintf(ifr.ifr_name, IFNAMSIZ, "tun_%d", getpid());

Nit: it might be better to accept the device name instead of repeating
the snprintf trick here, this would facilitate the future changes.

I am not sure I understand what did you mean by "accept the device name"
here.

The above is used to get ifindex of the tun netdevice created in
tun_alloc(), so that we can use it in vdev_send_packet() to send
a packet using the tun netdevice created in tun_alloc(). Is there
anything obvious I missed here?

I meant a const char *ifname for this function and let the caller to
pass the name.

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+       assert(ioctl(dev->sock, SIOCGIFINDEX, &ifr) >= 0);
+
+       dev->ifindex = ifr.ifr_ifindex;
+
+       /* Set the flags that bring the device up */
+       assert(ioctl(dev->sock, SIOCGIFFLAGS, &ifr) >= 0);
+       ifr.ifr_flags |= (IFF_UP | IFF_RUNNING);
+       assert(ioctl(dev->sock, SIOCSIFFLAGS, &ifr) >= 0);
+}
+
+static void vdev_send_packet(struct vdev_info *dev)
+{
+       char *sendbuf = dev->test_buf + HDR_LEN;
+       struct sockaddr_ll saddrll = {0};
+       int sockfd = dev->sock;
+       int ret;
+
+       saddrll.sll_family = PF_PACKET;
+       saddrll.sll_ifindex = dev->ifindex;
+       saddrll.sll_halen = ETH_ALEN;
+       saddrll.sll_protocol = htons(TEST_PTYPE);
+
+       ret = sendto(sockfd, sendbuf, TEST_BUF_LEN, 0,
+                    (struct sockaddr *)&saddrll,
+                    sizeof(struct sockaddr_ll));
+       assert(ret >= 0);
+}
+

...

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+
+static void vq_info_add(struct vdev_info *dev, int idx, int num, int fd)
+{
+       struct vhost_vring_file backend = { .index = idx, .fd = fd };
+       struct vq_info *info = &dev->vqs[idx];
+       int r;
+
+       info->idx = idx;
+       info->kick = eventfd(0, EFD_NONBLOCK);
+       info->call = eventfd(0, EFD_NONBLOCK);

If we don't care about the callback, let's just avoid to set the call here?

(As I see vq_callback is a NULL)

Sure, will remove the vq_callback related code.

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+       r = posix_memalign(&info->ring, 4096, vring_size(num, 4096));
+       assert(r >= 0);
+       vq_reset(info, num, &dev->vdev);
+       vhost_vq_setup(dev, info);
+       info->fds.fd = info->call;
+       info->fds.events = POLLIN;
+
+       r = ioctl(dev->control, VHOST_NET_SET_BACKEND, &backend);
+       assert(!r);
+}
+
+static void vdev_info_init(struct vdev_info *dev, unsigned long long features)
+{
+       struct ether_header *eh;
+       int i, r;
+
+       dev->vdev.features = features;
+       INIT_LIST_HEAD(&dev->vdev.vqs);
+       spin_lock_init(&dev->vdev.vqs_list_lock);
+
+       dev->buf_size = (HDR_LEN + TEST_BUF_LEN) * 2;
+       dev->buf = malloc(dev->buf_size);
+       assert(dev->buf);
+       dev->test_buf = dev->buf;
+       dev->res_buf = dev->test_buf + HDR_LEN + TEST_BUF_LEN;
+
+       memset(dev->test_buf, 0, HDR_LEN + TEST_BUF_LEN);
+       eh = (struct ether_header *)(dev->test_buf + HDR_LEN);
+       eh->ether_type = htons(TEST_PTYPE);
+       memcpy(eh->ether_dhost, dev->mac, ETHER_ADDR_LEN);
+       memcpy(eh->ether_shost, dev->mac, ETHER_ADDR_LEN);
+
+       for (i = sizeof(*eh); i < TEST_BUF_LEN; i++)
+               dev->test_buf[i + HDR_LEN] = (char)i;
+
+       dev->control = open("/dev/vhost-net", O_RDWR);
+       assert(dev->control >= 0);
+
+       r = ioctl(dev->control, VHOST_SET_OWNER, NULL);
+       assert(r >= 0);
+
+       dev->mem = malloc(offsetof(struct vhost_memory, regions) +
+                         sizeof(dev->mem->regions[0]));
+       assert(dev->mem);
+       memset(dev->mem, 0, offsetof(struct vhost_memory, regions) +
+              sizeof(dev->mem->regions[0]));
+       dev->mem->nregions = 1;
+       dev->mem->regions[0].guest_phys_addr = (long)dev->buf;
+       dev->mem->regions[0].userspace_addr = (long)dev->buf;
+       dev->mem->regions[0].memory_size = dev->buf_size;
+
+       r = ioctl(dev->control, VHOST_SET_MEM_TABLE, dev->mem);
+       assert(r >= 0);
+
+       r = ioctl(dev->control, VHOST_SET_FEATURES, &features);
+       assert(r >= 0);
+
+       dev->nvqs = 2;
+}
+
+static void wait_for_interrupt(struct vq_info *vq)
+{
+       unsigned long long val;
+
+       poll(&vq->fds, 1, -1);
+
+       if (vq->fds.revents & POLLIN)
+               read(vq->fds.fd, &val, sizeof(val));
+}
+
+static void verify_res_buf(char *res_buf)
+{
+       int i;
+
+       for (i = ETHER_HDR_LEN; i < TEST_BUF_LEN; i++)
+               assert(res_buf[i] == (char)i);
+}
+
+static void run_tx_test(struct vdev_info *dev, struct vq_info *vq,
+                       bool delayed, int batch, int bufs)

It might be better to describe the test design briefly above as a
comment. Or we can start from simple test logic and add sophisticated
ones on top.

Does something described in the comment log as suggested by you make
sense to you?
Steps for vhost_net tx testing:
1. Prepare a out buf
2. Kick the vhost_net to do tx processing
3. Do the receiving in the tun side
4. verify the data received by tun is correct

See my reply above.

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+{
+       const bool random_batch = batch == RANDOM_BATCH;
+       long long spurious = 0;
+       struct scatterlist sl;
+       unsigned int len;
+       int r;
+
+       for (;;) {
+               long started_before = vq->started;
+               long completed_before = vq->completed;
+
+               virtqueue_disable_cb(vq->vq);
+               do {
+                       if (random_batch)
+                               batch = (random() % vq->vring.num) + 1;
+
+                       while (vq->started < bufs &&
+                              (vq->started - vq->completed) < batch) {
+                               sg_init_one(&sl, dev->test_buf, HDR_LEN + TEST_BUF_LEN);
+                               r = virtqueue_add_outbuf(vq->vq, &sl, 1,
+                                                        dev->test_buf + vq->started,
+                                                        GFP_ATOMIC);
+                               if (unlikely(r != 0)) {
+                                       if (r == -ENOSPC &&
+                                           vq->started > started_before)
+                                               r = 0;
+                                       else
+                                               r = -1;
+                                       break;
+                               }
+
+                               ++vq->started;
+
+                               if (unlikely(!virtqueue_kick(vq->vq))) {
+                                       r = -1;
+                                       break;
+                               }
+                       }
+
+                       if (vq->started >= bufs)
+                               r = -1;
+
+                       /* Flush out completed bufs if any */
+                       while (virtqueue_get_buf(vq->vq, &len)) {
+                               int n;
+
+                               n = recvfrom(dev->sock, dev->res_buf, TEST_BUF_LEN, 0, NULL, NULL);
+                               assert(n == TEST_BUF_LEN);
+                               verify_res_buf(dev->res_buf);
+
+                               ++vq->completed;
+                               r = 0;
+                       }
+               } while (r == 0);
+
+               if (vq->completed == completed_before && vq->started == started_before)
+                       ++spurious;
+
+               assert(vq->completed <= bufs);
+               assert(vq->started <= bufs);
+               if (vq->completed == bufs)
+                       break;
+
+               if (delayed) {
+                       if (virtqueue_enable_cb_delayed(vq->vq))
+                               wait_for_interrupt(vq);
+               } else {
+                       if (virtqueue_enable_cb(vq->vq))
+                               wait_for_interrupt(vq);
+               }
+       }
+       printf("TX spurious wakeups: 0x%llx started=0x%lx completed=0x%lx\n",
+              spurious, vq->started, vq->completed);
+}
+
+static void run_rx_test(struct vdev_info *dev, struct vq_info *vq,
+                       bool delayed, int batch, int bufs)
+{
+       const bool random_batch = batch == RANDOM_BATCH;
+       long long spurious = 0;
+       struct scatterlist sl;
+       unsigned int len;
+       int r;
+
+       for (;;) {
+               long started_before = vq->started;
+               long completed_before = vq->completed;
+
+               do {
+                       if (random_batch)
+                               batch = (random() % vq->vring.num) + 1;
+
+                       while (vq->started < bufs &&
+                              (vq->started - vq->completed) < batch) {
+                               sg_init_one(&sl, dev->res_buf, HDR_LEN + TEST_BUF_LEN);
+
+                               r = virtqueue_add_inbuf(vq->vq, &sl, 1,
+                                                       dev->res_buf + vq->started,
+                                                       GFP_ATOMIC);
+                               if (unlikely(r != 0)) {
+                                       if (r == -ENOSPC &&

Drivers usually maintain a #free_slots, this can help to avoid the
trick for checking ENOSPC?

The above "(vq->started - vq->completed) < batch" seems to ensure that
the 'r' can't be '-ENOSPC'?

Well, if this is true any reason we still check ENOSPEC here?

We just need to ensure the batch <= desc_num,
and the 'r == -ENOSPC' checking seems to be unnecessary.

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+                                           vq->started > started_before)
+                                               r = 0;
+                                       else
+                                               r = -1;
+                                       break;
+                               }
+
+                               ++vq->started;
+
+                               vdev_send_packet(dev);
+
+                               if (unlikely(!virtqueue_kick(vq->vq))) {
+                                       r = -1;
+                                       break;
+                               }
+                       }
+
+                       if (vq->started >= bufs)
+                               r = -1;
+
+                       /* Flush out completed bufs if any */
+                       while (virtqueue_get_buf(vq->vq, &len)) {
+                               struct ether_header *eh;
+
+                               eh = (struct ether_header *)(dev->res_buf + HDR_LEN);
+
+                               /* tun netdev is up and running, ignore the
+                                * non-TEST_PTYPE packet.
+                                */

I wonder if it's better to set up some kind of qdisc to avoid the
unexpected packet here, or is it too complicated?

Yes, at least I don't know to do that yet.

For example, the blackhole qdisc?

Thanks