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Re: [PATCH v3] util: support PCI passthrough net device stats collection



On 9/24/20 4:18 AM, zhenwei pi wrote:
Collect PCI passthrough net device stats from kernel by netlink
API.

Currently, libvirt can not get PCI passthrough net device stats,
run command:
  #virsh domifstat instance --interface=52:54:00:2d:b2:35
  error: Failed to get interface stats instance 52:54:00:2d:b2:35
  error: internal error: Interface name not provided

The PCI device(usually SR-IOV virtual function device) is detached
while it's used in PCI passthrough mode. And we can not parse this
device from /proc/net/dev any more.

In this patch, libvirt check net device is VF of not firstly, then
query virNetDevVFInterfaceStats(new API).
virNetDevVFInterfaceStats parses VFs info of all PFs, compares MAC
address until the two MAC addresses match.
'#ip -s link show' can get the same result. Instead of parsing the
output result, implement this feature by libnl API.

Notice that this feature deponds on driver of PF.
Test on Mellanox ConnectX-4 Lx, it works well.
Also test on Intel Corporation 82599ES, it works, but only get 0.
(ip-link command get the same result).

IFLA_VF_STATS is supported since Linux-4.2, suggested by Laine,
just using defined(__linux__) && WITH_LIBNL is enough.

Signed-off-by: zhenwei pi <pizhenwei bytedance com>
---
  src/libvirt_private.syms |   1 +
  src/qemu/qemu_driver.c   |   3 ++
  src/util/virnetdev.c     | 121 +++++++++++++++++++++++++++++++++++++++++++++++
  src/util/virnetdev.h     |   5 ++
  4 files changed, 130 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index bdbe3431b8..bcc40b8d69 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2585,6 +2585,7 @@ virNetDevSetRcvMulti;
  virNetDevSetupControl;
  virNetDevSysfsFile;
  virNetDevValidateConfig;
+virNetDevVFInterfaceStats;
# util/virnetdevbandwidth.h
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index ae715c01d7..f554010c40 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -10196,6 +10196,9 @@ qemuDomainInterfaceStats(virDomainPtr dom,
      if (virDomainNetGetActualType(net) == VIR_DOMAIN_NET_TYPE_VHOSTUSER) {
          if (virNetDevOpenvswitchInterfaceStats(net->ifname, stats) < 0)
              goto cleanup;
+    } else if (virDomainNetGetActualType(net) == VIR_DOMAIN_NET_TYPE_HOSTDEV) {
+        if (virNetDevVFInterfaceStats(&net->mac, stats) < 0)
+            goto cleanup;
      } else {
          if (virNetDevTapInterfaceStats(net->ifname, stats,
                                         !virDomainNetTypeSharesHostView(net)) < 0)
diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c
index e1a4cc2bef..3d54d07606 100644
--- a/src/util/virnetdev.c
+++ b/src/util/virnetdev.c
@@ -1489,6 +1489,7 @@ static struct nla_policy ifla_vf_policy[IFLA_VF_MAX+1] = {
                              .maxlen = sizeof(struct ifla_vf_mac) },
      [IFLA_VF_VLAN]      = { .type = NLA_UNSPEC,
                              .maxlen = sizeof(struct ifla_vf_vlan) },
+    [IFLA_VF_STATS]     = { .type = NLA_NESTED },
  };
@@ -2265,6 +2266,116 @@ virNetDevSetNetConfig(const char *linkdev, int vf,
      return 0;
  }
+static struct nla_policy ifla_vfstats_policy[IFLA_VF_STATS_MAX+1] = {
+    [IFLA_VF_STATS_RX_PACKETS]  = { .type = NLA_U64 },
+    [IFLA_VF_STATS_TX_PACKETS]  = { .type = NLA_U64 },
+    [IFLA_VF_STATS_RX_BYTES]    = { .type = NLA_U64 },
+    [IFLA_VF_STATS_TX_BYTES]    = { .type = NLA_U64 },
+    [IFLA_VF_STATS_BROADCAST]   = { .type = NLA_U64 },
+    [IFLA_VF_STATS_MULTICAST]   = { .type = NLA_U64 },
+};
+
+static int
+virNetDevParseVfStats(struct nlattr **tb, virMacAddrPtr mac,
+                      virDomainInterfaceStatsPtr stats)
+{
+    int ret = -1, len;
+    struct ifla_vf_mac *vf_lladdr;
+    struct nlattr *nla, *t[IFLA_VF_MAX+1];
+    struct nlattr *stb[IFLA_VF_STATS_MAX+1];
+
+    if (tb == NULL || mac == NULL || stats == NULL) {
+        return -1;
+    }
+
+    if (!tb[IFLA_VFINFO_LIST])
+        return -1;
+
+    len = nla_len(tb[IFLA_VFINFO_LIST]);
+
+    for (nla = nla_data(tb[IFLA_VFINFO_LIST]); nla_ok(nla, len);
+            nla = nla_next(nla, &len)) {
+        ret = nla_parse(t, IFLA_VF_MAX, nla_data(nla), nla_len(nla),
+                ifla_vf_policy);
+        if (ret < 0)
+            return -1;
+
+        if (t[IFLA_VF_MAC] == NULL) {
+            continue;
+        }
+
+        vf_lladdr = nla_data(t[IFLA_VF_MAC]);
+        if (virMacAddrCmpRaw(mac, vf_lladdr->mac)) {
+            continue;
+        }
+
+        if (t[IFLA_VF_STATS]) {
+            ret = nla_parse_nested(stb, IFLA_VF_STATS_MAX,
+                    t[IFLA_VF_STATS],
+                    ifla_vfstats_policy);
+            if (ret < 0)
+                return -1;
+
+            stats->rx_bytes = nla_get_u64(stb[IFLA_VF_STATS_RX_BYTES]);
+            stats->tx_bytes = nla_get_u64(stb[IFLA_VF_STATS_TX_BYTES]);
+            stats->rx_packets = nla_get_u64(stb[IFLA_VF_STATS_RX_PACKETS]);
+            stats->tx_packets = nla_get_u64(stb[IFLA_VF_STATS_TX_PACKETS]);
+        }
+        return 0;
+    }
+
+    return ret;
+}
+
+/**
+ * virNetDevVFInterfaceStats:
+ * @mac: MAC address of the VF interface
+ * @stats: returns stats of the VF interface
+ *
+ * Get the VF interface from kernel by netlink.
+ * Returns 0 on success, -1 on failure.
+ */
+int
+virNetDevVFInterfaceStats(virMacAddrPtr mac,
+                          virDomainInterfaceStatsPtr stats)
+{
+    int rc = -1;
+    void *nlData = NULL;
+    struct nlattr *tb[IFLA_MAX + 1] = {NULL, };
+    char *sysfsDevicePath = NULL;
+    DIR *dirp = NULL;
+    struct dirent *dp;
+
+    if (virDirOpen(&dirp, SYSFS_NET_DIR) < 0)
+        return -1;
+
+    /* get all PCI net devices, and parse VFs list from netlink API.
+     * compare MAC address, collect device stats if matching.
+     */


Sorry, I hate to bring this up only on v3 of the patches (In the initial version I hadn't looked at implementation details, only at build CI, and hadn't gotten back to look at the later versions before other people commented on also-macro-level issues), but we shouldn't be determining which VF stats of which PF to report by scanning through all the PFs until we find a VF with a matching MAC address. Aside from being really inefficient (you shouldn't need to get a dump of all interfaces, just of the one interface you're interested in), also the MAC address of a device isn't unique (although it usually is), so you can't be guaranteed this is the correct VF.

Instead we need to start with the PCI address in the virDomainHostdevDef associated with the VF (which can be retrieved with virDomainNetDefActualHostdev(net)) and then learn the name of the PF, and what the VF# is for this VF using virPCIGetVirtualFunctionInfo(), (*or even better* - that function refactored to be more like virHostdevNetDevice() - it provides exactly what you need, but is just located in a file (virhostdev.c) that shouldn't be referenced from virnetdev.c).

Once we know the PF device name and which VF, we can get the NetlinkDump *only* for that device, and then directly grab the details from the particular VFINFO in the list, rather than relying on a match of the (unreliable) MAC address.

Since I already have an idea of the change I'd like to see in virPCIGetVirtualFunctionInfo(), let me refactor that function (and a few surrounding) so that they're more generally useful, and I'll Cc the patch for it to you so that you can use the updated function. I'll try to do it in the next couple days.


+    while (virDirRead(dirp, &dp, SYSFS_NET_DIR) > 0) {
+        if (virNetDevSysfsFile(&sysfsDevicePath, dp->d_name, "device") < 0)
+            break;
+
+        if (virNetDevIsPCIDevice(sysfsDevicePath)) {
+            rc = virNetlinkDumpLink(dp->d_name, -1, &nlData, tb, 0, 0);
+            if (rc < 0) {
+                rc = -1;
+                goto cleanup;
+            }
+
+            rc = virNetDevParseVfStats(tb, mac, stats);
+            VIR_FREE(nlData);
+            if (rc == 0)
+                goto cleanup;
+        }
+        VIR_FREE(sysfsDevicePath);
+    }
+
+ cleanup:
+    VIR_FREE(sysfsDevicePath);
+    VIR_DIR_CLOSE(dirp);
+    return rc;
+}
#else /* defined(__linux__) && defined(WITH_LIBNL) && defined(IFLA_VF_MAX) */ @@ -2309,6 +2420,16 @@ virNetDevSetNetConfig(const char *linkdev G_GNUC_UNUSED,
  }
+int
+virNetDevVFInterfaceStats(virMacAddrPtr mac G_GNUC_UNUSED,
+                     virDomainInterfaceStatsPtr stats G_GNUC_UNUSED)
+{
+    virReportSystemError(ENOSYS, "%s",
+                         _("Unable to get VF net device stats on this platform"));
+    return -1;
+}
+
+
  #endif /* defined(__linux__) && defined(WITH_LIBNL) && defined(IFLA_VF_MAX) */
VIR_ENUM_IMPL(virNetDevIfState,
diff --git a/src/util/virnetdev.h b/src/util/virnetdev.h
index 5f581323ed..ff59d9d341 100644
--- a/src/util/virnetdev.h
+++ b/src/util/virnetdev.h
@@ -312,4 +312,9 @@ int virNetDevSysfsFile(char **pf_sysfs_device_link,
  int virNetDevRunEthernetScript(const char *ifname, const char *script)
      G_GNUC_NO_INLINE;
+int virNetDevVFInterfaceStats(virMacAddrPtr mac,
+                              virDomainInterfaceStatsPtr stats)
+ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
+
+
  G_DEFINE_AUTOPTR_CLEANUP_FUNC(virNetDevRxFilter, virNetDevRxFilterFree);



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