[PATCH v3 0/7] fix multi-process VF hotplug

longli
2026-02-25T13:58:38Z

This series fixes multi-process support for DPDK drivers used on
Azure VMs with Accelerated Networking (AN). When AN is toggled, the
VF device is hot-removed and hot-added, which can crash secondary
processes due to stale fast-path pointers and race conditions.

Patches 1-2 fix the netvsc PMD:
- Fix rwlock misuse and race conditions on VF add/remove events
- Add multi-process VF device removal support via IPC

Patches 3-4 fix resource leaks:
- MANA PD resource leak on device close
- netvsc devargs memory leak on hotplug

Patches 5-7 fix a common bug across MANA, MLX5, and MLX4 drivers
where the secondary process START_RXTX/STOP_RXTX IPC handlers
update dev->rx_pkt_burst/tx_pkt_burst but do not update the
process-local rte_eth_fp_ops[] array. Since rte_eth_rx_burst()
uses rte_eth_fp_ops (not dev->rx_pkt_burst), the secondary retains
stale queue data pointers after VF hot-add, causing a segfault.

Tested on Azure D8s_v3 (mlx5) with symmetric_mp primary+secondary.
AN disable/re-enable correctly hot-removes and re-attaches VF in
both processes without crash.

v3:
- Drop patch 1 from v2 (secondary ignore promiscuous enable/disable)
as it is no longer needed with the VF race condition fixes
- Patch 2: use #define for MZ_NETVSC_SHARED_DATA instead of const
char pointer
- Patch 2: simplify netvsc_secondary_handle_device_remove() to take
vf_port directly instead of struct hn_data pointer
- Patch 2: return 0 (not error) when VF port is not present in
secondary, as this is a normal condition during startup
- Patch 2: pass vf_port as parameter to netvsc_mp_req_vf() instead
of reading from hv->vf_ctx internally
- Patch 2: protect netvsc_init_once() and secondary_cnt increment
under same spinlock to prevent race between MP handler registration
and secondary count visibility
- Patch 2: add secondary_cnt decrement in error and cleanup paths
- Patch 2: fix misleading comment about cross-process locking

v2:
- Patch 1: rename __hn_vf_add/__hn_vf_remove to
hn_vf_add_unlocked/hn_vf_remove_unlocked to avoid C-reserved
double-underscore prefix (C99 7.1.3)
- Patch 1: add hn_vf_detach() cleanup path when VF configure/start
fails after hn_vf_attach() succeeds, preventing half-attached
VF state
- Patch 1: unconditionally clear vf_vsc_switched on VF remove
regardless of hn_nvs_set_datapath() result, since VF is being
removed anyway
- Patch 2: add rte_eth_dev_is_valid_port() check before accessing
rte_eth_devices[] in secondary VF removal handler
- Patch 2: rename netvsc_mp_req_VF to netvsc_mp_req_vf per DPDK
lowercase naming convention
- Patch 2: use rte_memory_order_acquire/release instead of relaxed
for secondary_cnt to ensure visibility on ARM
- Patch 2: initialize ret = 0 in netvsc_init_once()
- Patch 3: use local 'err' variable for ibv_dealloc_pd() return
value to avoid shadowing outer 'ret'

Long Li (7):
net/netvsc: fix race conditions on VF add/remove events
net/netvsc: add multi-process VF device removal support
net/mana: fix PD resource leak on device close
net/netvsc: fix devargs memory leak on hotplug
net/mana: fix fast-path ops setup in secondary process
net/mlx5: fix fast-path ops setup in secondary process
net/mlx4: fix fast-path ops setup in secondary process

drivers/net/mana/mana.c | 14 ++
drivers/net/mana/mp.c | 6 +
drivers/net/mlx4/mlx4_mp.c | 4 +
drivers/net/mlx5/linux/mlx5_mp_os.c | 4 +
drivers/net/netvsc/hn_ethdev.c | 287 +++++++++++++++++++++++++++-
drivers/net/netvsc/hn_nvs.h | 5 +
drivers/net/netvsc/hn_rxtx.c | 40 ++--
drivers/net/netvsc/hn_var.h | 1 +
drivers/net/netvsc/hn_vf.c | 144 ++++++++------
9 files changed, 417 insertions(+), 88 deletions(-)

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2.43.0