Re: [PATCH 18/20] scsi: ibmvfc: fix NVMe sub-queue registration failure disabling SCSI multiqueue

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] ibmvfc: permanent loss of NVMe MQ after transient registration failure
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commit 3196ff84a81b6364f0d8e7add637cd7dce662d03
Author: Tyrel Datwyler <tyreld@linux.ibm.com>

scsi: ibmvfc: fix NVMe sub-queue registration failure disabling SCSI multiqueue

This commit modifies ibmvfc_reg_sub_crqs() to check the channel protocol
during registration failure. It clears vhost->do_enquiry for SCSI failures
and vhost->nvme_enabled for NVMe failures, preventing NVMe registration
failures from silently disabling SCSI multiqueue support.

> diff --git a/drivers/scsi/ibmvscsi/ibmvfc-core.c b/drivers/scsi/ibmvscsi/ibmvfc-core.c
> index 93189692191e3..d79a6ae278a2c 100644
> --- a/drivers/scsi/ibmvscsi/ibmvfc-core.c
> +++ b/drivers/scsi/ibmvscsi/ibmvfc-core.c
> @@ -6527,7 +6527,10 @@ static void ibmvfc_reg_sub_crqs(struct ibmvfc_host *vhost,
>  		if (ibmvfc_register_channel(vhost, channels, i)) {
>  			for (j = i; j > 0; j--)
>  				ibmvfc_deregister_channel(vhost, channels, j - 1);
> -			vhost->do_enquiry = 0;
> +			if (channels->protocol == IBMVFC_PROTO_SCSI)
> +				vhost->do_enquiry = 0;
> +			else
> +				vhost->nvme_enabled = 0;

[Severity: High]
Does this permanently disable NVMe multiqueue support if an NVMe sub-queue
registration failure is transient?

When an NVMe registration fails, vhost->nvme_enabled is now set to 0.
The host will eventually reset and retry registration, for example via
ibmvfc_reset_crq() or ibmvfc_reenable_crq_queue().

Unlike vhost->do_enquiry which is explicitly restored to 1 during reset:

ibmvfc_reset_crq() {
	...
	vhost->do_enquiry = 1;
	vhost->using_channels = 0;
	vhost->do_scsi_login = 0;
	vhost->do_nvme_login = 0;
	...
}

vhost->nvme_enabled is never restored.

If the subsequent registration retry succeeds, the NVMe channels are
successfully registered with the hypervisor, but nvme_enabled remains 0.
Could this prevent the driver from advertising IBMVFC_YES_NVMEOF during
NPIV login, leaving the newly registered channels permanently unused by the
VIOS and breaking the multiqueue recovery mechanism?

>  			return;
>  		}
>  	}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260916230921.2204729-1-tyreld@linux.ibm.com?part=18