MAX_MBUF_SIZE causes queue configuration failure.

[David Marchand]

Hello,

On Wed, Apr 12, 2023 at 8:59 AM Dhamodaran Pandiyan
<dhamodaran.it15 at gmail.com> wrote:
>
> When I set the value to MAX_MBUF_SIZE as less than 16256, all the initialization went through fine and the application was online.
>
> But when I increase the MAX_MBUF_SIZE to more than 16256 like 16257, 17000, or 18000, I get the attached log error which shows an issue in configuring the virtual queues for the NIC.
>
> Log Snip:
> i40evf_configure_vsi_queues(): Failed to execute command of VIRTCHNL_OP_CONFIG_VSI_QUEUES
> i40evf_dev_start(): configure queues failed

Added net/i40e driver maintainers.

This error indicates a failure either when sending a message to the PF
driver, or that the PF driver refused to configure this VF with the
passed parameters.
Assuming you are using the PF i40e driver, I tracked this message
handling to find that buffer size is limited (the exact limit is not
clear to me) probably due to some hw limitations.

See:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c#n4088
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c#n2371
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c#n714

/* max pkt. length validation */
if (info->max_pkt_size >= (16 * 1024) || info->max_pkt_size < 64) {
    ret = -EINVAL;
    goto error_param;
}

I'll let net/i40e reply with better details/explanations.


> MTU size for port id:  is: 9000
> Failed to start the fast pkt for port_id : 1Ret: -1
>
> Some Observations:
> 1. Thought memory availability was an issue, so provided 10x more memory and allocated 10x huge pages than required, still noticed the same issue.
> 2. Got to know MTU size also plays a role in deciding the mbuf_size, so tried running app with MTU of less value, but still issue persists.
>
> Please someone enlighten me on what is happening here.



-- 
David Marchand