linux-kernel - Re: [PATCH v7 06/15] s390/vfio-ap: sysfs attribute to display the guest CRYCB

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Message-ID: <60c6bfb6-dd0a-75dc-1043-8dffe983220a@linux.ibm.com>
Date:   Wed, 8 Apr 2020 12:38:49 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ux.ibm.com, borntraeger@...ibm.com,
        mjrosato@...ux.ibm.com, pmorel@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        jjherne@...ux.ibm.com, fiuczy@...ux.ibm.com
Subject: Re: [PATCH v7 06/15] s390/vfio-ap: sysfs attribute to display the
 guest CRYCB



On 4/8/20 6:33 AM, Cornelia Huck wrote:
> On Tue,  7 Apr 2020 15:20:06 -0400
> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>
>> The matrix of adapters and domains configured in a guest's CRYCB may
>> differ from the matrix of adapters and domains assigned to the matrix mdev,
>> so this patch introduces a sysfs attribute to display the CRYCB of a guest
>> using the matrix mdev. For a matrix mdev denoted by $uuid, the crycb for a
>> guest using the matrix mdev can be displayed as follows:
>>
>>     cat /sys/devices/vfio_ap/matrix/$uuid/guest_matrix
>>
>> If a guest is not using the matrix mdev at the time the crycb is displayed,
>> an error (ENODEV) will be returned.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c | 58 +++++++++++++++++++++++++++++++
>>   1 file changed, 58 insertions(+)
>> +static DEVICE_ATTR_RO(guest_matrix);
> Hm... should information like the guest configuration be readable by
> everyone? Or should it be restricted a bit more?

Why? The matrix attribute already displays the APQNs of the queues
assigned to the matrix mdev. The guest_matrix attribute merely displays
a subset of the matrix (i.e., the APQNs assigned to the mdev that reference
queue devices bound to the vfio_ap device driver).

How can this be restricted?

>
>> +
>>   static struct attribute *vfio_ap_mdev_attrs[] = {
>>   	&dev_attr_assign_adapter.attr,
>>   	&dev_attr_unassign_adapter.attr,
>> @@ -1050,6 +1107,7 @@ static struct attribute *vfio_ap_mdev_attrs[] = {
>>   	&dev_attr_unassign_control_domain.attr,
>>   	&dev_attr_control_domains.attr,
>>   	&dev_attr_matrix.attr,
>> +	&dev_attr_guest_matrix.attr,
>>   	NULL,
>>   };
>>