netdev - RE: [Intel-wired-lan] [PATCH net v2] i40e: fix endless loop under rtnl

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Message-ID: <PH0PR11MB50959F0358EEED7AB520D4C5D6AA9@PH0PR11MB5095.namprd11.prod.outlook.com>
Date:   Thu, 30 Sep 2021 21:23:02 +0000
From:   "Keller, Jacob E" <jacob.e.keller@...el.com>
To:     Jiri Benc <jbenc@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
Subject: RE: [Intel-wired-lan] [PATCH net v2] i40e: fix endless loop under
 rtnl

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of Jiri
> Benc
> Sent: Tuesday, September 14, 2021 1:55 AM
> To: netdev@...r.kernel.org
> Cc: intel-wired-lan@...ts.osuosl.org
> Subject: [Intel-wired-lan] [PATCH net v2] i40e: fix endless loop under rtnl
> 
> The loop in i40e_get_capabilities can never end. The problem is that
> although i40e_aq_discover_capabilities returns with an error if there's
> a firmware problem, the returned error is not checked. There is a check for
> pf->hw.aq.asq_last_status but that value is set to I40E_AQ_RC_OK on most
> firmware problems.
> 
> When i40e_aq_discover_capabilities encounters a firmware problem, it will
> enocunter the same problem on its next invocation. As the result, the loop
> becomes endless. We hit this with I40E_ERR_ADMIN_QUEUE_TIMEOUT but
> looking
> at the code, it can happen with a range of other firmware errors.
> 
> I don't know what the correct behavior should be: whether the firmware
> should be retried a few times, or whether pf->hw.aq.asq_last_status should
> be always set to the encountered firmware error (but then it would be
> pointless and can be just replaced by the i40e_aq_discover_capabilities
> return value). However, the current behavior with an endless loop under the
> rtnl mutex(!) is unacceptable and Intel has not submitted a fix, although we
> explained the bug to them 7 months ago.
> 
> This may not be the best possible fix but it's better than hanging the whole
> system on a firmware bug.

Yea this is a strict improvement.

> 
> Fixes: 56a62fc86895 ("i40e: init code and hardware support")
> Tested-by: Stefan Assmann <sassmann@...hat.com>
> Signed-off-by: Jiri Benc <jbenc@...hat.com>
> ---
> v2: added the Fixes tag, no code changes
> ---
>  drivers/net/ethernet/intel/i40e/i40e_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c
> b/drivers/net/ethernet/intel/i40e/i40e_main.c
> index 2f20980dd9a5..b5b984754ec9 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
> @@ -10113,7 +10113,7 @@ static int i40e_get_capabilities(struct i40e_pf *pf,
>  		if (pf->hw.aq.asq_last_status == I40E_AQ_RC_ENOMEM) {
>  			/* retry with a larger buffer */
>  			buf_len = data_size;
> -		} else if (pf->hw.aq.asq_last_status != I40E_AQ_RC_OK) {
> +		} else if (pf->hw.aq.asq_last_status != I40E_AQ_RC_OK || err) {
>  			dev_info(&pf->pdev->dev,
>  				 "capability discovery failed, err %s aq_err %s\n",
>  				 i40e_stat_str(&pf->hw, err),
> --
> 2.18.1
> 
> _______________________________________________
> Intel-wired-lan mailing list
> Intel-wired-lan@...osl.org
> https://lists.osuosl.org/mailman/listinfo/intel-wired-lan

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