netdevsim: allow normal queue reset while down

Resetting queues while the device is down should be legal.
Allow it, test it. Ideally we'd test this with a real device
supporting devmem but I don't have access to such devices.

Reviewed-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20250206225638.1387810-5-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/netdevsim/netdev.c

@@ -645,8 +645,11 @@ nsim_queue_mem_alloc(struct net_device *dev, void *per_queue_mem, int idx)
 	if (ns->rq_reset_mode > 3)
 		return -EINVAL;
 
-	if (ns->rq_reset_mode == 1)
+	if (ns->rq_reset_mode == 1) {
+		if (!netif_running(ns->netdev))
+			return -ENETDOWN;
 		return nsim_create_page_pool(&qmem->pp, &ns->rq[idx]->napi);
+	}
 
 	qmem->rq = nsim_queue_alloc();
 	if (!qmem->rq)
@@ -754,11 +757,6 @@ nsim_qreset_write(struct file *file, const char __user *data,
 		return -EINVAL;
 
 	rtnl_lock();
-	if (!netif_running(ns->netdev)) {
-		ret = -ENETDOWN;
-		goto exit_unlock;
-	}
-
 	if (queue >= ns->netdev->real_num_rx_queues) {
 		ret = -EINVAL;
 		goto exit_unlock;

tools/testing/selftests/net/nl_netdev.py

@@ -35,6 +35,21 @@ def napi_list_check(nf) -> None:
                         comment=f"queue count after reset queue {q} mode {i}")
 
 
+def nsim_rxq_reset_down(nf) -> None:
+    """
+    Test that the queue API supports resetting a queue
+    while the interface is down. We should convert this
+    test to testing real HW once more devices support
+    queue API.
+    """
+    with NetdevSimDev(queue_count=4) as nsimdev:
+        nsim = nsimdev.nsims[0]
+
+        ip(f"link set dev {nsim.ifname} down")
+        for i in [0, 2, 3]:
+            nsim.dfs_write("queue_reset", f"1 {i}")
+
+
 def page_pool_check(nf) -> None:
     with NetdevSimDev() as nsimdev:
         nsim = nsimdev.nsims[0]
@@ -106,7 +121,8 @@ def get_pp():
 
 def main() -> None:
     nf = NetdevFamily()
-    ksft_run([empty_check, lo_check, page_pool_check, napi_list_check],
+    ksft_run([empty_check, lo_check, page_pool_check, napi_list_check,
+              nsim_rxq_reset_down],
              args=(nf, ))
     ksft_exit()