linux-kernel - Re: [PATCH v5 10/13] s390: vfio-ap: sysfs interface to view matrix mdev matrix

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Date:   Thu, 24 May 2018 11:10:44 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, kwankhede@...dia.com,
        bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, pmorel@...ux.vnet.ibm.com,
        alifm@...ux.vnet.ibm.com, mjrosato@...ux.vnet.ibm.com,
        jjherne@...ux.vnet.ibm.com, thuth@...hat.com,
        pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com
Subject: Re: [PATCH v5 10/13] s390: vfio-ap: sysfs interface to view matrix
 mdev matrix

On 23/05/2018 16:38, Tony Krowiak wrote:
> On 05/16/2018 03:55 AM, Pierre Morel wrote:
>> On 07/05/2018 17:11, Tony Krowiak wrote:
>>> Provides a sysfs interface to view the AP matrix configured for the
>>> mediated matrix device.
>>>
>>> The relevant sysfs structures are:
>>>
>>> /sys/devices/vfio_ap
>>> ... [matrix]
>>> ...... [mdev_supported_types]
>>> ......... [vfio_ap-passthrough]
>>> ............ [devices]
>>> ...............[$uuid]
>>> .................. matrix
>>>
>>> To view the matrix configured for the mediated matrix device,
>>> print the matrix file:
>>
>> This is the configured matrix, not the one used by the guest.
>> Nothing in the patches protect against binding a queue and assigning
>> a new AP when the guest runs.
>> The card and queue will be showed by this entry.
>
> Of course, as stated above, this is the matrix configured for the
> mediated matrix device. Are you suggesting here that the driver
> should prevent assigning a new adapter or domain while a guest is
> running? Couldn't this be a step in the process for hot (un)plugging
> AP queues?

No, I mean what is the point to show this?
It is not what the guest sees.
Has it any use case?

>
>>
>>
>>
>>>
>>>     cat matrix
>>>
>>> Signed-off-by: Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
>>> ---
>>>   drivers/s390/crypto/vfio_ap_ops.c |   31 
>>> +++++++++++++++++++++++++++++++
>>>   1 files changed, 31 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
>>> b/drivers/s390/crypto/vfio_ap_ops.c
>>> index 755be1d..81e03b8 100644
>>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>>> @@ -716,6 +716,36 @@ static ssize_t control_domains_show(struct 
>>> device *dev,
>>>   }
>>>   DEVICE_ATTR_RO(control_domains);
>>>
>>> +static ssize_t matrix_show(struct device *dev, struct 
>>> device_attribute *attr,
>>> +               char *buf)
>>> +{
>>> +    struct mdev_device *mdev = mdev_from_dev(dev);
>>> +    struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>>> +    char *bufpos = buf;
>>> +    unsigned long apid;
>>> +    unsigned long apqi;
>>> +    unsigned long napm = matrix_mdev->matrix.apm_max + 1;
>>> +    unsigned long naqm = matrix_mdev->matrix.aqm_max + 1;
>>> +    int nchars = 0;
>>> +    int n;
>>> +
>>> +    for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, napm) {
>>> +        n = sprintf(bufpos, "%02lx\n", apid);
>>> +        bufpos += n;
>>> +        nchars += n;
>>> +
>>> +        for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, naqm) {
>>> +            n = sprintf(bufpos, "%02lx.%04lx\n", apid, apqi);
>>> +            bufpos += n;
>>> +            nchars += n;
>>> +        }
>>> +    }
>>> +
>>> +    return nchars;
>>> +}
>>> +DEVICE_ATTR_RO(matrix);
>>> +
>>> +
>>>   static struct attribute *vfio_ap_mdev_attrs[] = {
>>>       &dev_attr_assign_adapter.attr,
>>>       &dev_attr_unassign_adapter.attr,
>>> @@ -724,6 +754,7 @@ static ssize_t control_domains_show(struct 
>>> device *dev,
>>>       &dev_attr_assign_control_domain.attr,
>>>       &dev_attr_unassign_control_domain.attr,
>>>       &dev_attr_control_domains.attr,
>>> +    &dev_attr_matrix.attr,
>>>       NULL,
>>>   };
>>>
>>
>

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