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Cisco Bug: CSCvs60000 - Timeouts due to vNIC soft reset and vnic hang

Last Modified

Oct 13, 2020

Products (1)

  • Cisco UCS Virtual Interface Card

Known Affected Releases

4.0(4d)A 4.1(1a)C

Description (partial)

Symptom:
Timeouts, due to vnic 'enic_softreset' and vnic 'hang_notify'.

This is due to an improper handling of a memory allocation failure in the enic driver.

This is not limited to NFS setups: any setup that runs into a low-memory condition can potentially experience this issue.

May also lead to a kernel panic. (Depending on workload and operations)

Conditions:
Running Linux based OS (Also seen in Citrix XEN hypervisors)

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Running ENIC Driver versions between 3.2.210.27 (included) and 4.0.0.8-802.24 (excluded).

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Depending on the vnic configuration, and more specifically the number of RX/TX queues and how those queues are paired, you may see the bug manifest differently.

When the issue affects a TX queue, it will lead to a WATCHDOG timeout, which will trigger an interface reset.

When the issue affects a RX queue, the latter will not be able to properly receive any more packets and all ingress packets addresses to that RX queue will be dropped in hardware (and reflected in the "rx_no_buf" counter which you can check with the "ethtool -S <interface_name>" command). Note that when an RX queue experiences this issue, other RX queues on the same interface will still work fine, and this explains why you may see only a subset of the traffic being dropped (ie, the traffic that happens to land on the bad RX queue).
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