linux-kernel - Re: [PATCH v3 7/9] s390: ap: implement PAPQ AQIC interception in kernel

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Message-Id: <7f50ca6d-c0a5-e252-554b-b62b11629f1f@linux.ibm.com>
Date:   Thu, 21 Feb 2019 13:50:26 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Halil Pasic <pasic@...ux.ibm.com>
Cc:     borntraeger@...ibm.com, 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, akrowiak@...ux.ibm.com, david@...hat.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v3 7/9] s390: ap: implement PAPQ AQIC interception in
 kernel

On 20/02/2019 12:54, Halil Pasic wrote:
> On Thu, 14 Feb 2019 14:51:07 +0100
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
> 
>> We register the AP PQAP instruction hook during the open
>> of the mediated device. And unregister it on release.
>>
>> In the AP PQAP instruction hook, if we receive a demand to
>> enable IRQs,
>> - we retrieve the vfio_ap_queue based on the APQN we receive
>>    in REG1,
>> - we retrieve the page of the guest address, (NIB), from
>>    register REG2
>> - we the mediated device to use the VFIO pinning infratrsucture
>>    to pin the page of the guest address,
>> - we retrieve the pointer to KVM to register the guest ISC
>>    and retrieve the host ISC
>> - finaly we activate GISA
>>
>> If we receive a demand to disable IRQs,
>> - we deactivate GISA
>> - unregister from the GIB
>> - unping the NIB
>>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> ---
> 
> [..]
> 
>> +static int handle_pqap(struct kvm_vcpu *vcpu)
>> +{
>> +	uint64_t status;
>> +	uint16_t apqn;
>> +	struct vfio_ap_queue *q;
>> +	struct ap_queue_status qstatus = {};
>> +	struct ap_matrix_mdev *matrix_mdev;
>> +
>> +	/* If we do not use the AIV facility just go to userland */
>> +	if (!(vcpu->arch.sie_block->eca & ECA_AIV))
>> +		return -EOPNOTSUPP;
>> +
>> +	apqn = vcpu->run->s.regs.gprs[0] & 0xffff;
>> +	q = vfio_ap_get_queue(apqn);
>> +	if (!q) {
>> +		qstatus.response_code = AP_RESPONSE_Q_NOT_AVAIL;
>> +		goto out;
>> +	}
>> +
>> +	/* Check if the queue is associated with a guest matrix */
>> +	matrix_mdev = q->matrix;
>> +	if (!matrix_mdev || !matrix_mdev->kvm) {
>> +		qstatus.response_code = AP_RESPONSE_DECONFIGURED;
>> +		goto out;
>> +	}
>> +
>> +	status = vcpu->run->s.regs.gprs[1];
>> +
>> +	/* If IR bit(16) is set we enable the interrupt */
>> +	if ((status >> (63 - 16)) & 0x01) {
>> +		q->isc = status & 0x07;
>> +		q->nib = vcpu->run->s.regs.gprs[2];
> 
> Careful! You may already have q->nib set (may or may not be a 0x07
> scenario). You should unpin the old nib if set interruption controls
> works out, if we get 0x07 response then you unpin the new one.

You are right. We already had this discussion and the corrected patch.
It seems I misunderstood what we wanted to do by sending this patch 
series out.

I will make this right.

regards,
Pierre


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