netdev - Re: [PATCH net] net: atlantic: fix warning during hot unplug

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Message-ID: <20250203100236.GB234677@kernel.org>
Date: Mon, 3 Feb 2025 10:02:36 +0000
From: Simon Horman <horms@...nel.org>
To: Jacob Moroni <mail@...emoroni.com>
Cc: Igor Russkikh <irusskikh@...vell.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: atlantic: fix warning during hot unplug

On Sun, Feb 02, 2025 at 05:09:21PM -0500, Jacob Moroni wrote:
> Firmware deinitialization performs MMIO accesses which are not
> necessary if the device has already been removed. In some cases,
> these accesses happen via readx_poll_timeout_atomic which ends up
> timing out, resulting in a warning at hw_atl2_utils_fw.c:112:
> 
> [  104.595913] Call Trace:
> [  104.595915]  <TASK>
> [  104.595918]  ? show_regs+0x6c/0x80
> [  104.595923]  ? __warn+0x8d/0x150
> [  104.595925]  ? aq_a2_fw_deinit+0xcf/0xe0 [atlantic]
> [  104.595934]  ? report_bug+0x182/0x1b0
> [  104.595938]  ? handle_bug+0x6e/0xb0
> [  104.595940]  ? exc_invalid_op+0x18/0x80
> [  104.595942]  ? asm_exc_invalid_op+0x1b/0x20
> [  104.595944]  ? aq_a2_fw_deinit+0xcf/0xe0 [atlantic]
> [  104.595952]  ? aq_a2_fw_deinit+0xcf/0xe0 [atlantic]
> [  104.595959]  aq_nic_deinit.part.0+0xbd/0xf0 [atlantic]
> [  104.595964]  aq_nic_deinit+0x17/0x30 [atlantic]
> [  104.595970]  aq_ndev_close+0x2b/0x40 [atlantic]
> [  104.595975]  __dev_close_many+0xad/0x160
> [  104.595978]  dev_close_many+0x99/0x170
> [  104.595979]  unregister_netdevice_many_notify+0x18b/0xb20
> [  104.595981]  ? __call_rcu_common+0xcd/0x700
> [  104.595984]  unregister_netdevice_queue+0xc6/0x110
> [  104.595986]  unregister_netdev+0x1c/0x30
> [  104.595988]  aq_pci_remove+0xb1/0xc0 [atlantic]
> 
> Fix this by skipping firmware deinitialization altogether if the
> PCI device is no longer present.
> 
> Tested with an AQC113 attached via Thunderbolt by performing
> repeated unplug cycles while traffic was running via iperf.
> 

Hi Jacob,

As a fix for net a Fixes tag should go here
(immediately before your signed-off-by line, no blank line in between).

I'm wondering if this one is appropriate: the problem seems
to go all the way back to here.

Fixes: 97bde5c4f909 ("net: ethernet: aquantia: Support for NIC-specific code")

> Signed-off-by: Jacob Moroni <mail@...emoroni.com>
> ---
>  drivers/net/ethernet/aquantia/atlantic/aq_nic.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
> index fe0e3e2a8117..e2ae95a01947 100644
> --- a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
> +++ b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
> @@ -1428,7 +1428,7 @@ void aq_nic_deinit(struct aq_nic_s *self, bool link_down)
>  	unsigned int i = 0U;
>  
>  	if (!self)
> -		goto err_exit;
> +		return;
>  
>  	for (i = 0U; i < self->aq_vecs; i++) {
>  		aq_vec = self->aq_vec[i];

This hunk, and the removal of the err_exit label, seem to be more
clean-up than addressing the bug described in the patch description.
I don't think they belong in this patch. But could be candidates for
a follow-up patch targeted at net-next.

> @@ -1441,13 +1441,14 @@ void aq_nic_deinit(struct aq_nic_s *self, bool link_down)
>  	aq_ptp_ring_free(self);
>  	aq_ptp_free(self);
>  
> -	if (likely(self->aq_fw_ops->deinit) && link_down) {
> -		mutex_lock(&self->fwreq_mutex);
> -		self->aq_fw_ops->deinit(self->aq_hw);
> -		mutex_unlock(&self->fwreq_mutex);
> +	/* May be invoked during hot unplug. */
> +	if (pci_device_is_present(self->pdev)) {
> +		if (likely(self->aq_fw_ops->deinit) && link_down) {

Maybe not important, but I would have written this as a single if
condition rather than two.

Also, not really appropriate to change in this patch as it's not part
of the bug, but I'm not sure that likely() is appropriate here:
is this a fast path?

> +			mutex_lock(&self->fwreq_mutex);
> +			self->aq_fw_ops->deinit(self->aq_hw);
> +			mutex_unlock(&self->fwreq_mutex);
> +		}
>  	}
> -
> -err_exit:;
>  }
>  
>  void aq_nic_free_vectors(struct aq_nic_s *self)

-- 
pw-bot: changes-requested