linux-kernel - Re: [PATCH v1 4/7] vfio: ap: AP Queue Interrupt Control VFIO ioctl calls

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Date:   Wed, 7 Nov 2018 23:23:40 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     borntraeger@...ibm.com, alex.williamson@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, frankja@...ux.ibm.com, akrowiak@...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 4/7] vfio: ap: AP Queue Interrupt Control VFIO ioctl
 calls

On 07/11/2018 10:46, Cornelia Huck wrote:
> On Wed, 31 Oct 2018 19:12:54 +0100
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
> 
>> This is the implementation of the VFIO ioctl calls to handle
>> the AQIC interception and use GISA to handle interrupts.
>>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c | 95 +++++++++++++++++++++++++++++++
>>   1 file changed, 95 insertions(+)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>> index 272ef427dcc0..f68102163bf4 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -895,12 +895,107 @@ static int vfio_ap_mdev_get_device_info(unsigned long arg)
>>   	return copy_to_user((void __user *)arg, &info, minsz);
>>   }
>>   
>> +static int ap_ioctl_setirq(struct ap_matrix_mdev *matrix_mdev,
>> +			   struct vfio_ap_aqic *parm)
>> +{
>> +	struct aqic_gisa aqic_gisa = reg2aqic(0);
>> +	struct kvm_s390_gisa *gisa = matrix_mdev->kvm->arch.gisa;
>> +	struct ap_status ap_status = reg2status(0);
>> +	unsigned long p;
>> +	int ret = -1;
>> +	int apqn;
>> +	uint32_t gd;
>> +
>> +	apqn = (int)(parm->cmd & 0xffff);
> 
> It seems you always use cmd & 0xffff only. What if there is other stuff
> in the remaining bits of cmd? Do you plan to ignore it in any case, or
> should you actively check that there is nothing in it?
> 

I do not think that the ioctl interface should reflect the hardware 
interface.
The ioctl interface ignores the remaining bits.
We ignore the FC because we obviously want to make a AQIC FC=3
We ignore the T bit.

But we receive the information from the intercepting software, i.e. QEMU 
which should I think do the checks before using the ioctl interface.

It seemed easier to me to pass the complete registers and to ignore some 
bits in them. In case we get any change in the future
But we could also only pass the APQN

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