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Why is MLXCENT_HW_TMP_ERR being logged against SR-IOV VF in errpt?

Question & Answer


Question

Why is MLXCENT_HW_TMP_ERR being logged against SR-IOV VF in errpt?
Setup:
VIOS: 3.1.4.41
Model: 9040-MR9
Firmware: FW950.50
ent0: PCIe3 2 PORT 25/10 Gb NIC&ROCE SFP28 ADAPTER VF
errpt:
LABEL:          MLXCENT_HW_TMP_ERR
IDENTIFIER:     1AD504C3

Date/Time:       Thu Jan 1 00:00:00 1970
Sequence Number: 0001
Machine Id:      00000000000
Node Id:         VIOS1
Class:           H
Type:            TEMP
WPAR:            Global
Resource Name:   ent0
Resource Class:  adapter
Resource Type:   b31516101e06
Location:        UXXXX.ND1.CSSYYYY-P1-C6-T1-S1
VPD:
      PCIe3 2 PORT 25/10 Gb NIC&ROCE SFP28 ADAPTER:
        Part Number.................01FT751
        EC Level....................P14620
        FRU Number..................01FT753
        Serial Number...............FF0F0F0F0FF
        Feature Code/Marketing ID...EC2U
        Customer Card ID Number.....FFF0
        Network Address.............FFFFFFFFFFFF
        ROM Level.(alterable).......001400301004
Description
Hardware temporary error
        Recommended Actions
        PERFORM PROBLEM DETERMINATION PROCEDURES
Detail Data
FILE NAME
line: 3090 file: entcore_response.c
MAC ADDRESS
FFFF FFFF FFFF
DEVICE DRIVER INTERNAL STATE
0000 0000 0000 0002 0000 0000 0000 0001 0000 0000 0000 0000
PCI ETHERNET STATISTICS
0000 FFFF 0000 00FF FFFF 0000 0000 FF00 FFFF 00FF 0000 FFFF 0000 FFFF 0000 0000

Answer

When changing an SR-IOV capable adapter from dedicated mode to sharing mode, the physical ports are automatically configured for 9000 MTU. However, when assigning a VF (logical port) from these physical ports to an AIX LPAR or VIOS, the VF on the OS does not have jumbo_frames enabled by default. Due to this mismatch, whenever the VF receives a large packet (>1500), it’s unable to DMA the packet to its’ buffer. This then triggers the “MLXCENT_HW_TMP_ERR” error to be logged.
If jumbo frames is not being used/configured on the network, any of the below options is a viable solution:
  1. Set MTU on the Physical Port via HMC GUI to 1500:
    1. On the HMC GUI, select the frame
    2. Click “Hardware virtualized I/O”
    3. Select the corresponding SR-IOV adapter
    4. Under “Physical Ports View”, select the physical port and click “Action” -> “Modify Physical Port”
    5. A popup will appear. Toggle open the “Advanced Section”
    6. Change MTU Size from 9000 to 1500 and click “Ok”
      HMC GUI: SR-IOV Adapter Port Advanced Section
       
  2.     Enable jumbo frames on VF adapter on the AIX LPAR/VIOS:
    1.  If VF entX is logging error, enable jumbo frames on that VF:
      • chdev -l entX -a jumbo_frames=yes -P
      • NOTE: If "auto_set_mtu" attribute is set to "yes" on the VF, MTU will automatically be set to 9000 on the interface, if interface enX is configured. Set auto_set_mtu to "no" to disable automatically setting MTU.
    2. Reboot the LPAR/VIOS for changes to take effect.
Additional Information:
SUPPORT

If you require more assistance, use the following step-by-step instructions to contact IBM to open a case for software with an active and valid support contract.  

1. Document (or collect screen captures of) all symptoms, errors, and messages related to your issue.

2. Capture any logs or data relevant to the situation.

3. Contact IBM to open a case:

   -For electronic support, see the IBM Support Community:
     https://www.ibm.com/mysupport
   -If you require telephone support, see the web page:
      https://www.ibm.com/planetwide/

4. Provide a clear, concise description of the issue.

 - For more information, see: Working with IBM AIX Support: Describing the problem.

5. If the system is accessible, collect a system snap, and upload all of the details and data for your case.

 - For more information, see: Working with IBM AIX Support: Collecting snap data
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Author:
Tim George

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Product Synonym

AIX; PowerVM

Document Information

Modified date:
30 May 2025

UID

ibm17234893

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