linux-kernel - Re: [PATCH] s390/vfio-ap: handle response code 01 on queue reset

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Date:   Wed, 29 Nov 2023 18:12:34 +0100
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     jjherne@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        frankja@...ux.ibm.com, imbrenda@...ux.ibm.com, david@...hat.com
Subject: Re: [PATCH] s390/vfio-ap: handle response code 01 on queue reset

Am 29.11.23 um 15:35 schrieb Tony Krowiak:
> In the current implementation, response code 01 (AP queue number not valid)
> is handled as a default case along with other response codes returned from
> a queue reset operation that are not handled specifically. Barring a bug,
> response code 01 will occur only when a queue has been externally removed
> from the host's AP configuration; nn this case, the queue must
> be reset by the machine in order to avoid leaking crypto data if/when the
> queue is returned to the host's configuration. The response code 01 case
> will be handled specifically by logging a WARN message followed by cleaning
> up the IRQ resources.
> 

To me it looks like this can be triggered by the LPAR admin, correct? So it
is not desireable but possible.
In that case I prefer to not use WARN, maybe use dev_warn or dev_err instead.
WARN can be a disruptive event if panic_on_warn is set.


> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
> ---
>   drivers/s390/crypto/vfio_ap_ops.c | 31 +++++++++++++++++++++++++++++++
>   1 file changed, 31 insertions(+)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 4db538a55192..91d6334574d8 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -1652,6 +1652,21 @@ static int apq_status_check(int apqn, struct ap_queue_status *status)
>   		 * a value indicating a reset needs to be performed again.
>   		 */
>   		return -EAGAIN;
> +	case AP_RESPONSE_Q_NOT_AVAIL:
> +		/*
> +		 * This response code indicates the queue is not available.
> +		 * Barring a bug, response code 01 will occur only when a queue
> +		 * has been externally removed from the host's AP configuration;
> +		 * in which case, the queue must be reset by the machine in
> +		 * order to avoid leaking crypto data if/when the queue is
> +		 * returned to the host's configuration. In this case, let's go
> +		 * ahead and log a warning message and return 0 so the AQIC
> +		 * resources get cleaned up by the caller.
> +		 */
> +		WARN(true,
> +		     "Unable to reset queue %02x.%04x: not in host AP configuration\n",
> +		     AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
> +			return 0;
>   	default:
>   		WARN(true,
>   		     "failed to verify reset of queue %02x.%04x: TAPQ rc=%u\n",
> @@ -1736,6 +1751,22 @@ static void vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q)
>   		q->reset_status.response_code = 0;
>   		vfio_ap_free_aqic_resources(q);
>   		break;
> +	case AP_RESPONSE_Q_NOT_AVAIL:
> +		/*
> +		 * This response code indicates the queue is not available.
> +		 * Barring a bug, response code 01 will occur only when a queue
> +		 * has been externally removed from the host's AP configuration;
> +		 * in which case, the queue must be reset by the machine in
> +		 * order to avoid leaking crypto data if/when the queue is
> +		 * returned to the host's configuration. In this case, let's go
> +		 * ahead and log a warning message then clean up the AQIC
> +		 * resources.
> +		 */
> +		WARN(true,
> +		     "Unable to reset queue %02x.%04x: not in host AP configuration\n",
> +		     AP_QID_CARD(q->apqn), AP_QID_QUEUE(q->apqn));
> +		vfio_ap_free_aqic_resources(q);
> +		break;
>   	default:
>   		WARN(true,
>   		     "PQAP/ZAPQ for %02x.%04x failed with invalid rc=%u\n",