linux-kernel - Re: [PATCH v4 3/7] s390: ap: associate a ap_vfio

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Message-Id: <b18828eb-0fd1-2fdc-f104-16c5ed8fd8cb@linux.ibm.com>
Date:   Mon, 4 Mar 2019 11:19:40 +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 v4 3/7] s390: ap: associate a ap_vfio_queue and a matrix
 mdev

On 04/03/2019 03:09, Halil Pasic wrote:
> On Fri, 22 Feb 2019 16:29:56 +0100
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
> 
>> We need to associate the ap_vfio_queue, which will hold the
>> per queue information for interrupt with a matrix mediated device
>> which hold the configuration and the way to the CRYCB.
> [..]
>> +static int vfio_ap_get_all_domains(struct ap_matrix_mdev *matrix_mdev, int apid)
>> +{
>> +	int apqi, apqn;
>> +	int ret = 0;
>> +	struct vfio_ap_queue *q;
>> +	struct list_head q_list;
>> +
>> +	INIT_LIST_HEAD(&q_list);
>> +
>> +	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS) {
>> +		apqn = AP_MKQID(apid, apqi);
>> +		q = vfio_ap_get_queue(apqn, &matrix_dev->free_list);
>> +		if (!q) {
>> +			ret = -EADDRNOTAVAIL;
>> +			goto rewind;
>> +		}
>> +		if (q->matrix_mdev) {
>> +			ret = -EADDRINUSE;
> 
> You tried to get the q from matrix_dev->free_list thus modulo races
> q->matrix_mdev should be 0. This change breaks the error codes in a
> sense that it becomes impossible to provoke EADDRINUSE (the proper
> error code for taken by another matrix_mdev).
> 

right.
I will change this.

Regards,
Pierre

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