linux-kernel - Re: [PATCH v9 17/22] s390: vfio-ap: zeroize the AP queues.

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Date:   Wed, 15 Aug 2018 16:36:32 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>,
        Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com,
        frankja@...ux.ibm.com
Subject: Re: [PATCH v9 17/22] s390: vfio-ap: zeroize the AP queues.

On 08/15/2018 12:24 PM, Cornelia Huck wrote:
> On Mon, 13 Aug 2018 17:48:14 -0400
> Tony Krowiak <akrowiak@...ux.vnet.ibm.com> wrote:
>
> Nit: please drop the leading period in the subject.

I assume you mean the ending period?

>
>> From: Tony Krowiak <akrowiak@...ux.ibm.com>
>>
>> Let's call PAPQ(ZAPQ) to zeroize a queue:
>>
>> * For each queue configured for a mediated matrix device
>>    when it is released.
>>
>> Zeroizing a queue resets the queue, clears all pending
>> messages for the queue entries and disables adapter interruptions
>> associated with the queue.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> Reviewed-by: Halil Pasic <pasic@...ux.ibm.com>
>> Tested-by: Michael Mueller <mimu@...ux.ibm.com>
>> Tested-by: Farhan Ali <alifm@...ux.ibm.com>
>> Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c     |   25 +++++++++++++++++++++++++
>>   drivers/s390/crypto/vfio_ap_private.h |   25 +++++++++++++++++++++++++
>>   2 files changed, 50 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
>> index 3e8534b..34f982a 100644
>> --- a/drivers/s390/crypto/vfio_ap_private.h
>> +++ b/drivers/s390/crypto/vfio_ap_private.h
>> @@ -74,4 +74,29 @@ struct ap_matrix_mdev {
>>   extern int vfio_ap_mdev_register(void);
>>   extern void vfio_ap_mdev_unregister(void);
>>   
>> +static inline int vfio_ap_reset_queue(unsigned int apid, unsigned int apqi,
>> +				      unsigned int retry)
>> +{
>> +	struct ap_queue_status status;
>> +
>> +	do {
>> +		status = ap_zapq(AP_MKQID(apid, apqi));
>> +		switch (status.response_code) {
>> +		case AP_RESPONSE_NORMAL:
>> +			return 0;
>> +		case AP_RESPONSE_RESET_IN_PROGRESS:
>> +		case AP_RESPONSE_BUSY:
>> +			msleep(20);
>> +			break;
>> +		default:
>> +			pr_warn("%s: error zeroizing %02x.%04x: response code %d\n",
>> +				VFIO_AP_MODULE_NAME, apid, apqi,
>> +				status.response_code);
> How can we end up here? Does this mean that we just don't know what to
> do with this response, or is this something that should never happen?
> (How much sense does it make to print an error?)

There are additional response codes that could be returned; for example,
in the case of a catastrophic failure such as: The function can not be
performed because the AP was somehow deconfigured or the functiona
cannot be performed due to a machine check failure that caused the AP
path to be removed. It shouldn't happen, but all are possibilities.
I can get rid of the message and just return -EIO if you prefer.

>
>> +			return -EIO;
>> +		}
>> +	} while (retry--);
>> +
>> +	return -EBUSY;
>> +}
>> +
>>   #endif /* _VFIO_AP_PRIVATE_H_ */