On 6/23/26 12:17, Jose Ignacio Tornos Martinez wrote:

After commit ad7c7b2172c3 ("net: hold netdev instance lock during sysfs
operations"), iavf_set_mac() is called with the netdev instance lock
already held.

The function queues a MAC address change request via
iavf_replace_primary_mac() and then waits for completion. However, in
the current flow, the actual virtchnl message is sent by the watchdog
task, which also needs to acquire the netdev lock to run. Additionally,
the adminq_task which processes virtchnl responses also needs the netdev
lock.

This creates a deadlock scenario:
1. iavf_set_mac() holds netdev lock and waits for MAC change
2. Watchdog needs netdev lock to send the request -> blocked
3. Even if request is sent, adminq_task needs netdev lock to process
    PF response -> blocked
4. MAC change times out after 2.5 seconds
5. iavf_set_mac() returns -EAGAIN

This particularly affects VFs during bonding setup when multiple VFs are
enslaved in quick succession.

Fix by implementing a synchronous MAC change operation similar to the
approach used in commit fdadbf6e84c4 ("iavf: fix incorrect reset handling
in callbacks").

The solution:
1. Send the virtchnl ADD_ETH_ADDR message directly (not via watchdog)
2. Poll the admin queue hardware directly for responses
3. Process all received messages (including non-MAC messages)
4. Return when MAC change completes or times out

A new generic function iavf_poll_virtchnl_response() is introduced that
can be reused for any future synchronous virtchnl operations. It takes a
callback to check completion, allowing flexible condition checking.

This allows the operation to complete synchronously while holding
netdev_lock, without relying on watchdog or adminq_task. The function
can sleep for up to 2.5 seconds polling hardware, but this is acceptable
since netdev_lock is per-device and only serializes operations on the
same interface.

To support this, change iavf_add_ether_addrs() to return an error code
instead of void, allowing callers to detect failures. Additionally,
export iavf_mac_add_reject() to enable proper rollback on local failures
(timeouts, send errors) - PF rejections are already handled automatically
by iavf_virtchnl_completion().

Remove vc_waitqueue entirely because iavf_set_mac was the only waiter on
this waitqueue and after the changes it is not needed.

Fixes: ad7c7b2172c3 ("net: hold netdev instance lock during sysfs operations")
cc: stable@vger.kernel.org
Signed-off-by: Jose Ignacio Tornos Martinez <redacted>
---
v7: Rebase on current net tree
     Remove the multi-batch processing loop from version 6 according to Przemek
     Kitszel review: the loop cannot work without polling between iterations
     since the second call would fail the current_op check. Multi-batch scenario
     is extremely rare; send first batch and let watchdog handle remainder as v5
     did

I was fine with v5 already, so:
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>

(we will see if Sashiko reads changelog notes (--- section here))