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

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Message-ID: <1f4720d7-93f1-4e38-a3ad-abaf99596e7c@linux.ibm.com>
Date:   Mon, 4 Dec 2023 09:53:50 -0500
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...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



On 11/29/23 12:12, Christian Borntraeger wrote:
> 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.

Yes, it can be triggered by the LPAR admin. I can't use dev_warn here 
because we don't have a reference to any device, but I can use pr_warn 
if that suffices.

> 
> 
>> 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",