virtio-net: dynamic network offloads configuration

Virtio-net driver currently negotiates network offloads
on startup via features mechanism and have no ability to
disable and re-enable offloads later.
This patch introduced a new control command that allows
to configure device network offloads state dynamically.
The patch also introduces a new feature flag
VIRTIO_NET_F_CTRL_GUEST_OFFLOADS.

Signed-off-by: Dmitry Fleytman <dfleytma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-id: 20130520081814.GA8162@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/net/virtio-net.c

@@ -359,6 +359,34 @@ static uint32_t virtio_net_bad_features(VirtIODevice *vdev)
     return features;
 }
 
+static void virtio_net_apply_guest_offloads(VirtIONet *n)
+{
+    tap_set_offload(qemu_get_subqueue(n->nic, 0)->peer,
+            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_CSUM)),
+            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_TSO4)),
+            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_TSO6)),
+            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_ECN)),
+            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_UFO)));
+}
+
+static uint64_t virtio_net_guest_offloads_by_features(uint32_t features)
+{
+    static const uint64_t 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);
+
+    return guest_offloads_mask & features;
+}
+
+static inline uint64_t virtio_net_supported_guest_offloads(VirtIONet *n)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(n);
+    return virtio_net_guest_offloads_by_features(vdev->guest_features);
+}
+
 static void virtio_net_set_features(VirtIODevice *vdev, uint32_t features)
 {
     VirtIONet *n = VIRTIO_NET(vdev);
@@ -369,12 +397,9 @@ static void virtio_net_set_features(VirtIODevice *vdev, uint32_t features)
     virtio_net_set_mrg_rx_bufs(n, !!(features & (1 << VIRTIO_NET_F_MRG_RXBUF)));
 
     if (n->has_vnet_hdr) {
-        tap_set_offload(qemu_get_subqueue(n->nic, 0)->peer,
+        n->curr_guest_offloads =
-                        (features >> VIRTIO_NET_F_GUEST_CSUM) & 1,
+            virtio_net_guest_offloads_by_features(features);
-                        (features >> VIRTIO_NET_F_GUEST_TSO4) & 1,
+        virtio_net_apply_guest_offloads(n);
-                        (features >> VIRTIO_NET_F_GUEST_TSO6) & 1,
-                        (features >> VIRTIO_NET_F_GUEST_ECN)  & 1,
-                        (features >> VIRTIO_NET_F_GUEST_UFO)  & 1);
     }
 
     for (i = 0;  i < n->max_queues; i++) {
@@ -420,6 +445,43 @@ static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd,
     return VIRTIO_NET_OK;
 }
 
+static int virtio_net_handle_offloads(VirtIONet *n, uint8_t cmd,
+                                     struct iovec *iov, unsigned int iov_cnt)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(n);
+    uint64_t offloads;
+    size_t s;
+
+    if (!((1 << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) & vdev->guest_features)) {
+        return VIRTIO_NET_ERR;
+    }
+
+    s = iov_to_buf(iov, iov_cnt, 0, &offloads, sizeof(offloads));
+    if (s != sizeof(offloads)) {
+        return VIRTIO_NET_ERR;
+    }
+
+    if (cmd == VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET) {
+        uint64_t supported_offloads;
+
+        if (!n->has_vnet_hdr) {
+            return VIRTIO_NET_ERR;
+        }
+
+        supported_offloads = virtio_net_supported_guest_offloads(n);
+        if (offloads & ~supported_offloads) {
+            return VIRTIO_NET_ERR;
+        }
+
+        n->curr_guest_offloads = offloads;
+        virtio_net_apply_guest_offloads(n);
+
+        return VIRTIO_NET_OK;
+    } else {
+        return VIRTIO_NET_ERR;
+    }
+}
+
 static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
                                  struct iovec *iov, unsigned int iov_cnt)
 {
@@ -590,6 +652,8 @@ static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
             status = virtio_net_handle_vlan_table(n, ctrl.cmd, iov, iov_cnt);
         } else if (ctrl.class == VIRTIO_NET_CTRL_MQ) {
             status = virtio_net_handle_mq(n, ctrl.cmd, iov, iov_cnt);
+        } else if (ctrl.class == VIRTIO_NET_CTRL_GUEST_OFFLOADS) {
+            status = virtio_net_handle_offloads(n, ctrl.cmd, iov, iov_cnt);
         }
 
         s = iov_from_buf(elem.in_sg, elem.in_num, 0, &status, sizeof(status));
@@ -1110,6 +1174,10 @@ static void virtio_net_save(QEMUFile *f, void *opaque)
             qemu_put_be32(f, n->vqs[i].tx_waiting);
         }
     }
+
+    if ((1 << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) & vdev->guest_features) {
+        qemu_put_be64(f, n->curr_guest_offloads);
+    }
 }
 
 static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
@@ -1167,15 +1235,6 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
             error_report("virtio-net: saved image requires vnet_hdr=on");
             return -1;
         }
-
-        if (n->has_vnet_hdr) {
-            tap_set_offload(qemu_get_queue(n->nic)->peer,
-                    (vdev->guest_features >> VIRTIO_NET_F_GUEST_CSUM) & 1,
-                    (vdev->guest_features >> VIRTIO_NET_F_GUEST_TSO4) & 1,
-                    (vdev->guest_features >> VIRTIO_NET_F_GUEST_TSO6) & 1,
-                    (vdev->guest_features >> VIRTIO_NET_F_GUEST_ECN)  & 1,
-                    (vdev->guest_features >> VIRTIO_NET_F_GUEST_UFO)  & 1);
-        }
     }
 
     if (version_id >= 9) {
@@ -1209,6 +1268,16 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
         }
     }
 
+    if ((1 << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) & vdev->guest_features) {
+        n->curr_guest_offloads = qemu_get_be64(f);
+    } else {
+        n->curr_guest_offloads = virtio_net_supported_guest_offloads(n);
+    }
+
+    if (peer_has_vnet_hdr(n)) {
+        virtio_net_apply_guest_offloads(n);
+    }
+
     virtio_net_set_queues(n);
 
     /* Find the first multicast entry in the saved MAC filter */

include/hw/i386/pc.h

@@ -217,6 +217,10 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
             .property = "vectors",\
             /* DEV_NVECTORS_UNSPECIFIED as a uint32_t string */\
             .value    = stringify(0xFFFFFFFF),\
+        },{ \
+            .driver   = "virtio-net-pci", \
+            .property = "ctrl_guest_offloads", \
+            .value    = "off", \
         },{\
             .driver   = "e1000",\
             .property = "romfile",\

include/hw/virtio/virtio-net.h

@@ -31,6 +31,8 @@
 /* The feature bitmap for virtio net */
 #define VIRTIO_NET_F_CSUM       0       /* Host handles pkts w/ partial csum */
 #define VIRTIO_NET_F_GUEST_CSUM 1       /* Guest handles pkts w/ partial csum */
+#define VIRTIO_NET_F_CTRL_GUEST_OFFLOADS 2 /* Control channel offload
+                                         * configuration support */
 #define VIRTIO_NET_F_MAC        5       /* Host has given MAC address. */
 #define VIRTIO_NET_F_GSO        6       /* Host handles pkts w/ any GSO type */
 #define VIRTIO_NET_F_GUEST_TSO4 7       /* Guest can handle TSOv4 in. */
@@ -190,6 +192,7 @@ typedef struct VirtIONet {
     size_t config_size;
     char *netclient_name;
     char *netclient_type;
+    uint64_t curr_guest_offloads;
 } VirtIONet;
 
 #define VIRTIO_NET_CTRL_MAC    1
@@ -229,6 +232,15 @@ struct virtio_net_ctrl_mq {
  #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN        1
  #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX        0x8000
 
+/*
+ * Control network offloads
+ *
+ * Dynamic offloads are available with the
+ * VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature bit.
+ */
+#define VIRTIO_NET_CTRL_GUEST_OFFLOADS   5
+ #define VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET        0
+
 #define DEFINE_VIRTIO_NET_FEATURES(_state, _field) \
         DEFINE_VIRTIO_COMMON_FEATURES(_state, _field), \
         DEFINE_PROP_BIT("csum", _state, _field, VIRTIO_NET_F_CSUM, true), \
@@ -249,6 +261,7 @@ struct virtio_net_ctrl_mq {
         DEFINE_PROP_BIT("ctrl_vlan", _state, _field, VIRTIO_NET_F_CTRL_VLAN, true), \
         DEFINE_PROP_BIT("ctrl_rx_extra", _state, _field, VIRTIO_NET_F_CTRL_RX_EXTRA, true), \
         DEFINE_PROP_BIT("ctrl_mac_addr", _state, _field, VIRTIO_NET_F_CTRL_MAC_ADDR, true), \
+        DEFINE_PROP_BIT("ctrl_guest_offloads", _state, _field, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, true), \
         DEFINE_PROP_BIT("mq", _state, _field, VIRTIO_NET_F_MQ, false)
 
 #define DEFINE_VIRTIO_NET_PROPERTIES(_state, _field)                           \