Subject: Re: [PATCH net v1] mlxbf_gige: open() should call request_irq() after NAPI init

From: Jiri Pirko <[email-masked]>
Date: Mon, 18 Mar 2024 12:40:16 +0100

Fri, Mar 15, 2024 at 03:56:09PM CET, [email-masked] wrote:
>This patch fixes an exception that occurs during open()

Don't talk about "this patch" in the patch description. Be imperative to
the codebase, tell it what to do. In both patch description and subject.
Much easier to follow then.

>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 #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.
>
>This patch fixes the issue by re-ordering the logic in mlxbf_gige open()
>so that the request_irq() calls execute after NAPI is fully initialized.

Same here.

>
>Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
>Signed-off-by: David Thompson <[email-masked]>
>Reviewed-by: Asmaa Mnebhi <[email-masked]>

The patch itself looks okay.

pw-bot: cr

>---
> .../mellanox/mlxbf_gige/mlxbf_gige_main.c     | 21 ++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
>diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
>index 3d09fa54598f..77134ca92938 100644
>--- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
>+++ b/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
>@@ -157,7 +154,7 @@ static int mlxbf_gige_open(struct net_device *netdev)
> 
> 	err = mlxbf_gige_tx_init(priv);
> 	if (err)
>-		goto free_irqs;
>+		goto phy_deinit;
> 	err = mlxbf_gige_rx_init(priv);
> 	if (err)
> 		goto tx_deinit;
>@@ -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 |
>@@ -182,11 +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);
> 
>-free_irqs:
>-	mlxbf_gige_free_irqs(priv);
>+phy_deinit:
>+	phy_stop(phydev);
> 	return err;
> }
> 
>-- 
>2.30.1
>
>