[PATCH v2 2/2] util: Add phys_port_name support on virPCIGetNetName

[Moshe Levi]

From: Dmytro Linkin <dlinkin at nvidia.com>

Current virPCIGetNetName() logic is to get net device name by checking
it's phys_port_id, if caller provide it, or by it's index (eg, by it's
position at sysfs net directory). This approach worked fine up until
linux kernel version 5.8, where NVIDIA Mellanox driver implemented
linking of VFs' representors to PF PCI address [1]

This mean
that device's sysfs net directory will hold multiple net devices. Ex.:

$ ls '/sys/bus/pci/devices/0000:82:00.0/net'
ens1f0  eth0  eth1

In switchdev mode the PF and the VF represntors support phys_port_name
In that case there is only a single netdev on the PCI device which is
the PF. The other net devices are the VF representors which we want
to exclude. whereas in the case of using phys_port_id, there could be
multiple PFs, and so we have to match the phys_port_id of the VF

virPCIGetNetName() will try to get PF name by it's index - 0. The
problem here is that the PF nedev entry may not be the first.

To fix that, for switch devices, we introduce a new logic to select the
PF uplink netdev according to the content of phys_port_name. Extend
virPCIGetNetName() logic work in following sequence:
 - filter by phys_port_id, if it's provided, (multi PF)
 or
 - filter by phys_port_name if exist (one PF)
 - get net device by it's index (position) in sysfs net directory.

[1] - https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/
      commit/?id=123f0f53dd64b67e34142485fe866a8a581f12f1

Co-Authored-by: Moshe Levi <moshele at nvidia.com>
Signed-off-by: Dmytro Linkin <dlinkin at nvidia.com>
Reviewed-by: Adrian Chiris <adrianc at nvidia.com>
---
 src/util/virnetdev.c |  7 +++----
 src/util/virpci.c    | 38 +++++++++++++++++++++++++++++++++++++-
 src/util/virpci.h    |  5 +++++
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c
index d41b967d6a..2485718b48 100644
--- a/src/util/virnetdev.c
+++ b/src/util/virnetdev.c
@@ -1263,7 +1263,7 @@ virNetDevGetVirtualFunctions(const char *pfname,
         }
 
         if (virPCIGetNetName(pci_sysfs_device_link, 0,
-                             pfPhysPortID, NULL, &((*vfname)[i])) < 0) {
+                             pfPhysPortID, &((*vfname)[i])) < 0) {
             goto cleanup;
         }
 
@@ -1358,8 +1358,7 @@ virNetDevGetPhysicalFunction(const char *ifname, char **pfname)
         return -1;
 
     if (virPCIGetNetName(physfn_sysfs_path, 0,
-                         vfPhysPortID,
-                         VIR_PF_PHYS_PORT_NAME_REGEX, pfname) < 0) {
+                         vfPhysPortID, pfname) < 0) {
         return -1;
     }
 
@@ -1422,7 +1421,7 @@ virNetDevPFGetVF(const char *pfname, int vf, char **vfname)
      * isn't bound to a netdev driver, it won't have a netdev name,
      * and vfname will be NULL).
      */
-    return virPCIGetNetName(virtfnSysfsPath, 0, pfPhysPortID, NULL, vfname);
+    return virPCIGetNetName(virtfnSysfsPath, 0, pfPhysPortID, vfname);
 }
 
 
diff --git a/src/util/virpci.c b/src/util/virpci.c
index 50fd5ef7ea..e20fb9e10b 100644
--- a/src/util/virpci.c
+++ b/src/util/virpci.c
@@ -2469,7 +2469,7 @@ virPCIDeviceAddressGetSysfsFile(virPCIDeviceAddressPtr addr,
  * @idx: used to choose which netdev when there are several
  *       (ignored if physPortID is set)
  * @physPortID: match this string in the netdev's phys_port_id
- *       (or NULL to ignore and use idx instead)
+ *       (or NULL to ignore and use phys_port_name or idx instead)
  * @netname: used to return the name of the netdev
  *       (set to NULL (but returns success) if there is no netdev)
  *
@@ -2483,6 +2483,7 @@ virPCIGetNetName(const char *device_link_sysfs_path,
 {
     g_autofree char *pcidev_sysfs_net_path = NULL;
     g_autofree char *firstEntryName = NULL;
+    g_autofree char *thisPhysPortName = NULL;
     g_autoptr(DIR) dir = NULL;
     struct dirent *entry = NULL;
     size_t i = 0;
@@ -2522,7 +2523,42 @@ virPCIGetNetName(const char *device_link_sysfs_path,
 
                 continue;
             }
+
         } else {
+            /* Most switch devices use phys_port_name instead of
+             * phys_port_id.
+             * NOTE: VFs' representors net devices can be linked to PF's PCI
+             * device, which mean that there'll be multiple net devices
+             * instances and to get a proper net device need to match on
+             * specific regex.
+             * To get PF netdev, for ex., used following regex:
+             * "(p[0-9]+$)|(p[0-9]+s[0-9]+$)"
+             * or to get exact VF's netdev next regex is used:
+             * "pf0vf1$"
+             */
+            if (virNetDevGetPhysPortName(entry->d_name, &thisPhysPortName) < 0)
+                return -1;
+
+            if (thisPhysPortName) {
+                /* if this one doesn't match, keep looking */
+                if (!virStringMatch(thisPhysPortName, VIR_PF_PHYS_PORT_NAME_REGEX)) {
+                    VIR_FREE(thisPhysPortName);
+                    /* Save the first entry we find to use as a failsafe
+                     * in case we fail to match on regex.
+                     */
+                    if (!firstEntryName)
+                        firstEntryName = g_strdup(entry->d_name);
+
+                    continue;
+                }
+            } else {
+                /* Save the first entry we find to use as a failsafe in case
+                 * phys_port_name is not supported.
+                 */
+                if (!firstEntryName)
+                    firstEntryName = g_strdup(entry->d_name);
+                continue;
+            }
             if (i++ < idx)
                 continue;
         }
diff --git a/src/util/virpci.h b/src/util/virpci.h
index 43828b0a8a..9e89ede1d5 100644
--- a/src/util/virpci.h
+++ b/src/util/virpci.h
@@ -55,6 +55,11 @@ struct _virZPCIDeviceAddress {
 
 #define VIR_PCI_DEVICE_ADDRESS_FMT "%04x:%02x:%02x.%d"
 
+/* Represents format of PF's phys_port_name in switchdev mode:
+ * 'p%u' or 'p%us%u'. New line checked since value is readed from sysfs file.
+ */
+# define VIR_PF_PHYS_PORT_NAME_REGEX  "(p[0-9]+$)|(p[0-9]+s[0-9]+$)"
+
 struct _virPCIDeviceAddress {
     unsigned int domain;
     unsigned int bus;
-- 
2.30.0