linux-kernel - Re: [PATCH v1 6/7] vfio: ap: register guest ISC with GISA and GIB

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Date:   Wed, 7 Nov 2018 23:40:42 +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 v1 6/7] vfio: ap: register guest ISC with GISA and GIB

On 06/11/2018 21:21, Tony Krowiak wrote:
> On 10/31/18 2:12 PM, Pierre Morel wrote:
>> Register to the GIB Alert list and retrieve the GAL_ISC
>> to pass to the GISA registration.
>>
>> Unregister on error and when clearing the interrupt.
>>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> Signed-off-by: Michael Mueller <mimu@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c | 16 +++++++++++++---
>>   1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
>> b/drivers/s390/crypto/vfio_ap_ops.c
>> index f68102163bf4..232168797fb8 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -903,16 +903,20 @@ static int ap_ioctl_setirq(struct ap_matrix_mdev 
>> *matrix_mdev,
>>       struct ap_status ap_status = reg2status(0);
>>       unsigned long p;
>>       int ret = -1;
>> -    int apqn;
>> +    int apqn, gal_isc;
>>       uint32_t gd;
>> +    gal_isc = kvm_s390_gisc_register(matrix_mdev->kvm, 
>> matrix_mdev->gisc);
>> +    if (gal_isc < 0)
>> +        return -EIO;
>> +
>>       apqn = (int)(parm->cmd & 0xffff);
>>       gd = matrix_mdev->kvm->vcpus[0]->arch.sie_block->gd;
>>       if (gd & 0x01)
>>           aqic_gisa.f = 1;
>>       aqic_gisa.gisc = matrix_mdev->gisc;
>> -    aqic_gisa.isc = GAL_ISC;
>> +    aqic_gisa.isc = gal_isc;
>>       aqic_gisa.ir = 1;
>>       aqic_gisa.gisao = gisa->next_alert >> 4;
>> @@ -923,7 +927,11 @@ static int ap_ioctl_setirq(struct ap_matrix_mdev 
>> *matrix_mdev,
>>       parm->status = ret;
>>       ap_status = reg2status(ret);
>> -    return (ap_status.rc) ? -EIO : 0;
>> +    if (ap_status.rc) {
>> +        kvm_s390_gisc_unregister(matrix_mdev->kvm, matrix_mdev->gisc);
>> +        return -EIO;
>> +    }
>> +    return 0;
>>   }
>>   static int ap_ioctl_clrirq(struct ap_matrix_mdev *matrix_mdev,
>> @@ -946,6 +954,8 @@ static int ap_ioctl_clrirq(struct ap_matrix_mdev 
>> *matrix_mdev,
>>       parm->status = retval;
>>       ap_status = reg2status(retval);
>> +    /* unregister the IAM from the GIB anyway! */
>> +    kvm_s390_gisc_unregister(matrix_mdev->kvm, matrix_mdev->gisc);
> 
> The case statement in patch 4 does not set mdev->gisc, so the
> presumption here is that VFIO_AP_SET_IRQ has been previously called and
> has set the value for matrix_mdev->gisc. Is it possible for
> VFIO_AP_CLEAR_IRQ to get invoked without a prior call to

right, I will check this.

However if the IRQ is not registered there is no problem as we will get 
an error when unregistering the IRQ
and unregistering the gisc 0 which was not registered will fail too.

But I think we better check before in case these functions change.

> VFIO_AP_SET_IRQ? In any case, shouldn't the GISC value be taken from
> bits 61-63 of 'parm'?

No this is not possible, the ISC field is not relevant when clearing 
interrupts.

> 
>>       return (ap_status.rc) ? -EIO : 0;
>>   }
>>
> 


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