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Subject: Re: [PATCH v6 13/21] s390: vfio-ap: sysfs interface to view matrix
 mdev matrix
To:     Tony Krowiak <akrowiak@linux.ibm.com>, pmorel@linux.ibm.com,
        Tony Krowiak <akrowiak@linux.vnet.ibm.com>,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
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        cohuck@redhat.com, kwankhede@nvidia.com,
        bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com,
        alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com,
        alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com,
        jjherne@linux.vnet.ibm.com, thuth@redhat.com,
        pasic@linux.vnet.ibm.com, berrange@redhat.com,
        fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com
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From:   Halil Pasic <pasic@linux.ibm.com>
Date:   Fri, 13 Jul 2018 18:38:52 +0200
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On 07/13/2018 02:24 PM, Tony Krowiak wrote:
> On 07/09/2018 04:38 PM, Pierre Morel wrote:
>> On 09/07/2018 14:20, Pierre Morel wrote:
>>> On 29/06/2018 23:11, 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:
>>>>
>>>>     cat matrix
>>>>
>>>> Signed-off-by: Tony Krowiak <akrowiak@linux.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 c8f31f3..bc7398d 100644
>>>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>>>> @@ -697,6 +697,36 @@ 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,
>>>> @@ -705,6 +735,7 @@ 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,
>>>>   };
>>>>
>>>
>>> I have still the same remark: what you show here is not what is currently
>>> used by the SIE.
>>> It is not irrelevant but what the guest really use may be more interesting
>>> for the admin.
>>>
>>>
>> OK, you implement the right view it in patch 16/21.
>>
>> Still, what is the purpose of showing this view?
> 
> I find it to have great value when configuring the mdev. It provides a view of
> what has been configured thus far.
> 

IMHO we need to keep this view for the reason stated by Tony.

Halil