When used with vhost kernel backend, we can offload at both directions.
- From vhost kernel to virtio_user, the offload is enabled so that
DPDK app can trust the flow is checksum-correct; and if DPDK app
sends it through another port, the checksum needs to be
recalculated or offloaded. It also applies to TSO.
- From virtio_user to vhost_kernel, the offload is enabled so that
kernel can trust the flow is L4-checksum-correct, no need to verify
it; if kernel will consume it, DPDK app should make sure the
l3-checksum is correctly set.
Signed-off-by: Jianfeng Tan <jianfeng....@intel.com>
---
drivers/net/virtio/virtio_user/vhost_kernel.c | 40 +++++++++++++++++++++--
drivers/net/virtio/virtio_user/vhost_kernel_tap.c | 14 ++++++++
drivers/net/virtio/virtio_user/vhost_kernel_tap.h | 7 ++++
3 files changed, 59 insertions(+), 2 deletions(-)
diff --git a/drivers/net/virtio/virtio_user/vhost_kernel.c
b/drivers/net/virtio/virtio_user/vhost_kernel.c
index 9301f96..a5d3e1e 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel.c
@@ -165,6 +165,28 @@ prepare_vhost_memory_kernel(void)
return vm;
}
+/* with below features, vhost kernel does not need to do the checksum and TSO,
+ * these info will be passed to virtio_user through virtio net header.
+ */
+#define VHOST_KERNEL_GUEST_OFFLOADS_MASK \
+ ((1ULL << VIRTIO_NET_F_GUEST_CSUM) | \
+ (1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
+ (1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
+ (1ULL << VIRTIO_NET_F_GUEST_ECN) | \
+ (1ULL << VIRTIO_NET_F_GUEST_UFO))
+
+/* with below features, when flows from virtio_user to vhost kernel
+ * (1) if flows goes up through the kernel networking stack, it does not need
+ * to verify checksum, which can save CPU cycles;
+ * (2) if flows goes through a Linux bridge and outside from an interface
+ * (kernel driver), checksum and TSO will be done by GSO in kernel or even
+ * offloaded into real physical device.
+ */
+#define VHOST_KERNEL_HOST_OFFLOADS_MASK \
+ ((1ULL << VIRTIO_NET_F_HOST_TSO4) | \
+ (1ULL << VIRTIO_NET_F_HOST_TSO6) | \
+ (1ULL << VIRTIO_NET_F_CSUM))
+
static int
vhost_kernel_ioctl(struct virtio_user_dev *dev,
enum vhost_user_request req,
@@ -186,10 +208,15 @@ vhost_kernel_ioctl(struct virtio_user_dev *dev,
arg = (void *)vm;
}
- /* We don't need memory protection here */
- if (req_kernel == VHOST_SET_FEATURES)
+ if (req_kernel == VHOST_SET_FEATURES) {
+ /* We don't need memory protection here */
*(uint64_t *)arg &= ~(1ULL << VIRTIO_F_IOMMU_PLATFORM);
+ /* VHOST kernel does not know about below flags */
+ *(uint64_t *)arg &= ~VHOST_KERNEL_GUEST_OFFLOADS_MASK;
+ *(uint64_t *)arg &= ~VHOST_KERNEL_HOST_OFFLOADS_MASK;
+ }
+
for (i = 0; i < dev->max_queue_pairs; ++i) {
if (dev->vhostfds[i] < 0)
continue;
@@ -199,6 +226,15 @@ vhost_kernel_ioctl(struct virtio_user_dev *dev,
break;
}
+ if (!ret && req_kernel == VHOST_GET_FEATURES) {
+ /* with tap as the backend, all these features are supported
+ * but not claimed by vhost-net, so we add them back when
+ * reporting to upper layer.
+ */
+ *((uint64_t *)arg) |= VHOST_KERNEL_GUEST_OFFLOADS_MASK;
+ *((uint64_t *)arg) |= VHOST_KERNEL_HOST_OFFLOADS_MASK;
+ }
+
if (vm)
free(vm);
diff --git a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
index 797713b..cdb5c3c 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
@@ -50,6 +50,12 @@ vhost_kernel_open_tap(char **p_ifname, int hdr_size)
int sndbuf = INT_MAX;
struct ifreq ifr;
int tapfd;
+ unsigned int offload =
+ TUN_F_CSUM |
+ TUN_F_TSO4 |
+ TUN_F_TSO6 |
+ TUN_F_TSO_ECN |
+ TUN_F_UFO;
/* TODO:
* 1. verify we can get/set vnet_hdr_len, tap_probe_vnet_hdr_len
@@ -106,6 +112,14 @@ vhost_kernel_open_tap(char **p_ifname, int hdr_size)
goto error;
}
+ /* TODO: before set the offload capabilities, we'd better (1) check
+ * negotiated features to see if necessary to offload; (2) query tap
+ * to see if it supports the offload capabilities.
+ */
+ if (ioctl(tapfd, TUNSETOFFLOAD, offload) != 0)
+ PMD_DRV_LOG(ERR, "TUNSETOFFLOAD ioctl() failed: %s",
+ strerror(errno));
+
if (!(*p_ifname))
*p_ifname = strdup(ifr.ifr_name);
diff --git a/drivers/net/virtio/virtio_user/vhost_kernel_tap.h
b/drivers/net/virtio/virtio_user/vhost_kernel_tap.h
index 1fc58ff..8535116 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel_tap.h
+++ b/drivers/net/virtio/virtio_user/vhost_kernel_tap.h
@@ -54,6 +54,13 @@
#define IFF_ATTACH_QUEUE 0x0200
#define IFF_DETACH_QUEUE 0x0400
+/* Features for GSO (TUNSETOFFLOAD). */
+#define TUN_F_CSUM 0x01 /* You can hand me unchecksummed packets. */
+#define TUN_F_TSO4 0x02 /* I can handle TSO for IPv4 packets */
+#define TUN_F_TSO6 0x04 /* I can handle TSO for IPv6 packets */
+#define TUN_F_TSO_ECN 0x08 /* I can handle TSO with ECN bits. */
+#define TUN_F_UFO 0x10 /* I can handle UFO packets */
+
/* Constants */
#define PATH_NET_TUN "/dev/net/tun"
--
2.7.4
