mlxbf_gige: call request_irq() after NAPI initialized

The mlxbf_gige driver encounters a NULL pointer exception in
mlxbf_gige_open() when kdump is enabled.  The sequence to reproduce
the exception is as follows:
a) enable kdump
b) trigger kdump via "echo c > /proc/sysrq-trigger"
c) kdump kernel executes
d) kdump kernel loads mlxbf_gige module
e) the mlxbf_gige module runs its open() as the
   the "oob_net0" interface is brought up
f) mlxbf_gige module will experience an exception
   during its open(), something like:

     Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
     Mem abort info:
       ESR = 0x0000000086000004
       EC = 0x21: IABT (current EL), IL = 32 bits
       SET = 0, FnV = 0
       EA = 0, S1PTW = 0
       FSC = 0x04: level 0 translation fault
     user pgtable: 4k pages, 48-bit VAs, pgdp=00000000e29a4000
     [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
     Internal error: Oops: 0000000086000004 [#1] SMP
     CPU: 0 PID: 812 Comm: NetworkManager Tainted: G           OE     5.15.0-1035-bluefield torvalds#37-Ubuntu
     Hardware name: https://www.mellanox.com BlueField-3 SmartNIC Main Card/BlueField-3 SmartNIC Main Card, BIOS 4.6.0.13024 Jan 19 2024
     pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
     pc : 0x0
     lr : __napi_poll+0x40/0x230
     sp : ffff800008003e00
     x29: ffff800008003e00 x28: 0000000000000000 x27: 00000000ffffffff
     x26: ffff000066027238 x25: ffff00007cedec00 x24: ffff800008003ec8
     x23: 000000000000012c x22: ffff800008003eb7 x21: 0000000000000000
     x20: 0000000000000001 x19: ffff000066027238 x18: 0000000000000000
     x17: ffff578fcb450000 x16: ffffa870b083c7c0 x15: 0000aaab010441d0
     x14: 0000000000000001 x13: 00726f7272655f65 x12: 6769675f6662786c
     x11: 0000000000000000 x10: 0000000000000000 x9 : ffffa870b0842398
     x8 : 0000000000000004 x7 : fe5a48b9069706ea x6 : 17fdb11fc84ae0d2
     x5 : d94a82549d594f35 x4 : 0000000000000000 x3 : 0000000000400100
     x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000066027238
     Call trace:
      0x0
      net_rx_action+0x178/0x360
      __do_softirq+0x15c/0x428
      __irq_exit_rcu+0xac/0xec
      irq_exit+0x18/0x2c
      handle_domain_irq+0x6c/0xa0
      gic_handle_irq+0xec/0x1b0
      call_on_irq_stack+0x20/0x2c
      do_interrupt_handler+0x5c/0x70
      el1_interrupt+0x30/0x50
      el1h_64_irq_handler+0x18/0x2c
      el1h_64_irq+0x7c/0x80
      __setup_irq+0x4c0/0x950
      request_threaded_irq+0xf4/0x1bc
      mlxbf_gige_request_irqs+0x68/0x110 [mlxbf_gige]
      mlxbf_gige_open+0x5c/0x170 [mlxbf_gige]
      __dev_open+0x100/0x220
      __dev_change_flags+0x16c/0x1f0
      dev_change_flags+0x2c/0x70
      do_setlink+0x220/0xa40
      __rtnl_newlink+0x56c/0x8a0
      rtnl_newlink+0x58/0x84
      rtnetlink_rcv_msg+0x138/0x3c4
      netlink_rcv_skb+0x64/0x130
      rtnetlink_rcv+0x20/0x30
      netlink_unicast+0x2ec/0x360
      netlink_sendmsg+0x278/0x490
      __sock_sendmsg+0x5c/0x6c
      ____sys_sendmsg+0x290/0x2d4
      ___sys_sendmsg+0x84/0xd0
      __sys_sendmsg+0x70/0xd0
      __arm64_sys_sendmsg+0x2c/0x40
      invoke_syscall+0x78/0x100
      el0_svc_common.constprop.0+0x54/0x184
      do_el0_svc+0x30/0xac
      el0_svc+0x48/0x160
      el0t_64_sync_handler+0xa4/0x12c
      el0t_64_sync+0x1a4/0x1a8
     Code: bad PC value
     ---[ end trace 7d1c3f3bf9d81885 ]---
     Kernel panic - not syncing: Oops: Fatal exception in interrupt
     Kernel Offset: 0x2870a7a00000 from 0xffff800008000000
     PHYS_OFFSET: 0x80000000
     CPU features: 0x0,000005c1,a3332a5a
     Memory Limit: none
     ---[ end Kernel panic - not syncing: Oops: Fatal exception in interrupt ]---

The exception happens because there is a pending RX interrupt before the
call to request_irq(RX IRQ) executes.  Then, the RX IRQ handler fires
immediately after this request_irq() completes. The RX IRQ handler runs
"napi_schedule()" before NAPI is fully initialized via "netif_napi_add()"
and "napi_enable()", both which happen later in the open() logic.

The logic in mlxbf_gige_open() must fully initialize NAPI before any calls
to request_irq() execute.

Fixes: f92e186 ("Add Mellanox BlueField Gigabit Ethernet driver")
Signed-off-by: David Thompson <davthompson@nvidia.com>
Reviewed-by: Asmaa Mnebhi <asmaa@nvidia.com>
Link: https://lore.kernel.org/r/20240325183627.7641-1-davthompson@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c

@@ -139,13 +139,10 @@ static int mlxbf_gige_open(struct net_device *netdev)
 	control |= MLXBF_GIGE_CONTROL_PORT_EN;
 	writeq(control, priv->base + MLXBF_GIGE_CONTROL);
 
-	err = mlxbf_gige_request_irqs(priv);
-	if (err)
-		return err;
 	mlxbf_gige_cache_stats(priv);
 	err = mlxbf_gige_clean_port(priv);
 	if (err)
-		goto free_irqs;
+		return err;
 
 	/* Clear driver's valid_polarity to match hardware,
 	 * since the above call to clean_port() resets the
@@ -166,6 +163,10 @@ static int mlxbf_gige_open(struct net_device *netdev)
 	napi_enable(&priv->napi);
 	netif_start_queue(netdev);
 
+	err = mlxbf_gige_request_irqs(priv);
+	if (err)
+		goto napi_deinit;
+
 	/* Set bits in INT_EN that we care about */
 	int_en = MLXBF_GIGE_INT_EN_HW_ACCESS_ERROR |
 		 MLXBF_GIGE_INT_EN_TX_CHECKSUM_INPUTS |
@@ -182,14 +183,17 @@ static int mlxbf_gige_open(struct net_device *netdev)
 
 	return 0;
 
+napi_deinit:
+	netif_stop_queue(netdev);
+	napi_disable(&priv->napi);
+	netif_napi_del(&priv->napi);
+	mlxbf_gige_rx_deinit(priv);
+
 tx_deinit:
 	mlxbf_gige_tx_deinit(priv);
 
 phy_deinit:
 	phy_stop(phydev);
-
-free_irqs:
-	mlxbf_gige_free_irqs(priv);
 	return err;
 }