linux-kernel - Re: [PATCH v4 6/7] s390: ap: Cleanup on removing the AP device

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Date:   Mon, 11 Mar 2019 09:31:02 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>, borntraeger@...ibm.com
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, frankja@...ux.ibm.com, pasic@...ux.ibm.com,
        david@...hat.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v4 6/7] s390: ap: Cleanup on removing the AP device

On 08/03/2019 23:43, Tony Krowiak wrote:
> On 2/22/19 10:29 AM, Pierre Morel wrote:
>> When the device is remove, we must make sure to
>> clear the interruption and reset the AP device.
>>
>> We also need to clear the CRYCB of the guest.
>>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_drv.c     | 35 
>> +++++++++++++++++++++++++++++++++++
>>   drivers/s390/crypto/vfio_ap_ops.c     |  3 ++-
>>   drivers/s390/crypto/vfio_ap_private.h |  3 +++
>>   3 files changed, 40 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_drv.c 
>> b/drivers/s390/crypto/vfio_ap_drv.c
>> index eca0ffc..e5d91ff 100644
>> --- a/drivers/s390/crypto/vfio_ap_drv.c
>> +++ b/drivers/s390/crypto/vfio_ap_drv.c
>> @@ -5,6 +5,7 @@
>>    * Copyright IBM Corp. 2018
>>    *
>>    * Author(s): Tony Krowiak <akrowiak@...ux.ibm.com>
>> + *          Pierre Morel <pmorel@...ux.ibm.com>
>>    */
>>   #include <linux/module.h>
>> @@ -12,6 +13,8 @@
>>   #include <linux/slab.h>
>>   #include <linux/string.h>
>>   #include <asm/facility.h>
>> +#include <linux/bitops.h>
>> +#include <linux/kvm_host.h>
>>   #include "vfio_ap_private.h"
>>   #define VFIO_AP_ROOT_NAME "vfio_ap"
>> @@ -61,6 +64,33 @@ static int vfio_ap_queue_dev_probe(struct ap_device 
>> *apdev)
>>   }
>>   /**
>> + * vfio_ap_update_crycb
>> + * @q: A pointer to the queue being removed
>> + *
>> + * We clear the APID of the queue, making this queue unusable for the 
>> guest.
>> + * After this function we can reset the queue without to fear a race 
>> with
>> + * the guest to access the queue again.
>> + * We do not fear race with the host as we still get the device.
>> + */
>> +static void vfio_ap_update_crycb(struct vfio_ap_queue *q)
>> +{
>> +    struct ap_matrix_mdev *matrix_mdev = q->matrix_mdev;
>> +
>> +    if (!matrix_mdev)
>> +        return;
>> +
>> +    clear_bit_inv(AP_QID_CARD(q->apqn), matrix_mdev->matrix.apm);
>> +
>> +    if (!matrix_mdev->kvm)
>> +        return;
>> +
>> +    kvm_arch_crypto_set_masks(matrix_mdev->kvm,
>> +                  matrix_mdev->matrix.apm,
>> +                  matrix_mdev->matrix.aqm,
>> +                  matrix_mdev->matrix.adm);
>> +}
>> +
>> +/**
>>    * vfio_ap_queue_dev_remove:
>>    *
>>    * Free the associated vfio_ap_queue structure
>> @@ -70,6 +100,11 @@ static void vfio_ap_queue_dev_remove(struct 
>> ap_device *apdev)
>>       struct vfio_ap_queue *q;
>>       q = dev_get_drvdata(&apdev->device);
>> +    if (!q)
>> +        return;
>> +
>> +    vfio_ap_update_crycb(q);
>> +    vfio_ap_mdev_reset_queue(q);
> 
> Since the bit corresponding to the APID is cleared in the
> vfio_ap_update_crycb() above, shouldn't all queues on that
> card also be reset?

I do not think so.
The remove function will be called in a loop for all queues by the bus.
No need to clear all queues.


> 
>>       list_del(&q->list);
>>       kfree(q);
>>   }
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
>> b/drivers/s390/crypto/vfio_ap_ops.c
>> index 0196065..5b9bb33 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -59,6 +59,7 @@ int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q)
>>               if (retry <= 0)
>>                   pr_warn("%s: queue 0x%04x not empty\n",
>>                       __func__, q->apqn);
>> +            vfio_ap_free_irq(q);
> 
> Shouldn't this be done for the response codes that terminate this loop
> such as those caught by the default case?

I do not think so, the error code is returned and the caller may want to 
reset the queue again.
I think that doing the free inside the call to reset is not right.
I will investigate in this direction.

Regards,
Pierre

-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany