linux-kernel - Re: [PATCH v2 5/5] ibmvfc: reinitialize sub-CRQs and perform channel enquiry after LPM

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Message-ID: <451323f3-e778-81d0-38e9-5f098ed3426c@linux.vnet.ibm.com>
Date:   Thu, 25 Feb 2021 15:17:50 -0600
From:   Brian King <brking@...ux.vnet.ibm.com>
To:     Tyrel Datwyler <tyreld@...ux.ibm.com>,
        james.bottomley@...senpartnership.com
Cc:     martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        brking@...ux.ibm.com
Subject: Re: [PATCH v2 5/5] ibmvfc: reinitialize sub-CRQs and perform channel
 enquiry after LPM

On 2/25/21 2:48 PM, Tyrel Datwyler wrote:
> A live partition migration (LPM) results in a CRQ disconnect similar to
> a hard reset. In this LPM case the hypervisor moslty perserves the CRQ
> transport such that it simply needs to be reenabled. However, the
> capabilities may have changed such as fewer channels, or no channels at
> all. Further, its possible that there may be sub-CRQ support, but no
> channel support. The CRQ reenable path currently doesn't take any of
> this into consideration.
> 
> For simpilicty release and reinitialize sub-CRQs during reenable, and
> set do_enquiry and using_channels with the appropriate values to trigger
> channel renegotiation.
> 
> Signed-off-by: Tyrel Datwyler <tyreld@...ux.ibm.com>
> ---
>  drivers/scsi/ibmvscsi/ibmvfc.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
> index 4ac2c442e1e2..9ae6be56e375 100644
> --- a/drivers/scsi/ibmvscsi/ibmvfc.c
> +++ b/drivers/scsi/ibmvscsi/ibmvfc.c
> @@ -903,6 +903,9 @@ static int ibmvfc_reenable_crq_queue(struct ibmvfc_host *vhost)
>  {
>  	int rc = 0;
>  	struct vio_dev *vdev = to_vio_dev(vhost->dev);
> +	unsigned long flags;
> +
> +	ibmvfc_release_sub_crqs(vhost);
>  
>  	/* Re-enable the CRQ */
>  	do {
> @@ -914,6 +917,16 @@ static int ibmvfc_reenable_crq_queue(struct ibmvfc_host *vhost)
>  	if (rc)
>  		dev_err(vhost->dev, "Error enabling adapter (rc=%d)\n", rc);
>  
> +	spin_lock_irqsave(vhost->host->host_lock, flags);
> +	spin_lock(vhost->crq.q_lock);
> +	vhost->do_enquiry = 1;
> +	vhost->using_channels = 0;
> +
> +	ibmvfc_init_sub_crqs(vhost);
> +
> +	spin_unlock(vhost->crq.q_lock);
> +	spin_unlock_irqrestore(vhost->host->host_lock, flags);

ibmvfc_init_sub_crqs can sleep, for multiple reasons, so you can't hold
a lock when you call it. There is a GFP_KERNEL allocation in it, and the
patch before this one adds an msleep in an error path.

Thanks,

Brian

-- 
Brian King
Power Linux I/O
IBM Linux Technology Center