[PATCH net v2] i40e: fix endless loop under rtnl

[PATCH net v2] i40e: fix endless loop under rtnl

[Jiri Benc]

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.

Fixes: 56a62fc86895 ("i40e: init code and hardware support")
Tested-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: Jiri Benc <jbenc@redhat.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

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

[Jesse Brandeburg]

On Tue, Sep 14, 2021 at 1:55 AM Jiri Benc <jbenc@redhat.com> wrote:
>
> 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.
>
> Fixes: 56a62fc86895 ("i40e: init code and hardware support")
> Tested-by: Stefan Assmann <sassmann@redhat.com>
> Signed-off-by: Jiri Benc <jbenc@redhat.com>


Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>

Thanks!

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

[Switzer, David]

-----Original Message-----
>From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of Jiri
>Benc
>Sent: Tuesday, September 14, 2021 1:55 AM
>To: netdev@vger.kernel.org
>Cc: intel-wired-lan@lists.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.
>
>Fixes: 56a62fc86895 ("i40e: init code and hardware support")
>Tested-by: Stefan Assmann <sassmann@redhat.com>
>Signed-off-by: Jiri Benc <jbenc@redhat.com>
Tested-by: Dave Switzer <david.switzer@intel.com>

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

[Keller, Jacob E]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of Jiri
> Benc
> Sent: Tuesday, September 14, 2021 1:55 AM
> To: netdev@vger.kernel.org
> Cc: intel-wired-lan@lists.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@redhat.com>
> Signed-off-by: Jiri Benc <jbenc@redhat.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
> 
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