Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v4 13/15] KVM: s390: configure the guest's AP devices
To:     Pierre Morel <pmorel@linux.vnet.ibm.com>,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     freude@de.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, borntraeger@de.ibm.com,
        cohuck@redhat.com, kwankhede@nvidia.com,
        bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com,
        alex.williamson@redhat.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
References: <1523827345-11600-1-git-send-email-akrowiak@linux.vnet.ibm.com>
 <1523827345-11600-14-git-send-email-akrowiak@linux.vnet.ibm.com>
 <2e7387b9-ceb4-cdca-56ac-f5344084e10a@linux.vnet.ibm.com>
 <c81ae786-1f37-e9b0-1f1a-1bb00180784c@linux.vnet.ibm.com>
 <105bce81-9359-6096-88ce-01ec1aef523e@linux.vnet.ibm.com>
From:   Tony Krowiak <akrowiak@linux.vnet.ibm.com>
Date:   Tue, 17 Apr 2018 12:36:33 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.0
MIME-Version: 1.0
In-Reply-To: <105bce81-9359-6096-88ce-01ec1aef523e@linux.vnet.ibm.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Message-Id: <6eb66344-d200-81d8-6533-aa1f9b53271e@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 04/17/2018 12:18 PM, Pierre Morel wrote:
> On 17/04/2018 18:08, Tony Krowiak wrote:
>> On 04/16/2018 09:05 AM, Pierre Morel wrote:
>>> On 15/04/2018 23:22, Tony Krowiak wrote:
>>>> Registers a group notifier during the open of the mediated
>>>> matrix device to get information on KVM presence through the
>>>> VFIO_GROUP_NOTIFY_SET_KVM event. When notified, the pointer
>>>> to the kvm structure is saved inside the mediated matrix
>>>> device. Once the VFIO AP device driver has access to KVM,
>>>> access to the APs can be configured for the guest.
>>>>
>>>> Access to APs is configured when the file descriptor for the
>>>> mediated matrix device is opened by userspace. The items to be
>>>> configured are:
>>>>
>>>> 1. The ECA.28 bit in the SIE state description determines whether
>>>>     AP instructions are interpreted by the hardware or intercepted.
>>>>     The VFIO AP device driver relies interpretive execution of
>>>>     AP instructions so the ECA.28 bit will be set
>>>>
>>>> 2. Guest access to AP adapters, usage domains and control domains
>>>>     is controlled by three bit masks referenced from the
>>>>     Crypto Control Block (CRYCB) referenced from the guest's SIE state
>>>>     description:
>>>>
>>>>     * The AP Mask (APM) controls access to the AP adapters. Each bit
>>>>       in the APM represents an adapter number - from most significant
>>>>       to least significant bit - from 0 to 255. The bits in the APM
>>>>       are set according to the adapter numbers assigned to the 
>>>> mediated
>>>>       matrix device via its 'assign_adapter' sysfs attribute file.
>>>>
>>>>     * The AP Queue (AQM) controls access to the AP queues. Each bit
>>>>       in the AQM represents an AP queue index - from most significant
>>>>       to least significant bit - from 0 to 255. A queue index 
>>>> references
>>>>       a specific domain and is synonymous with the domian number. The
>>>>       bits in the AQM are set according to the domain numbers assigned
>>>>       to the mediated matrix device via its 'assign_domain' sysfs
>>>>       attribute file.
>>>>
>>>>     * The AP Domain Mask (ADM) controls access to the AP control 
>>>> domains.
>>>>       Each bit in the ADM represents a control domain - from most
>>>>       significant to least significant bit - from 0-255. The
>>>>       bits in the ADM are set according to the domain numbers assigned
>>>>       to the mediated matrix device via its 'assign_control_domain'
>>>>       sysfs attribute file.
>>>>
>>>> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
>>>> ---
>>>>   drivers/s390/crypto/vfio_ap_ops.c     |   50 
>>>> +++++++++++++++++++++++++++++++++
>>>>   drivers/s390/crypto/vfio_ap_private.h |    2 +
>>>>   2 files changed, 52 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
>>>> b/drivers/s390/crypto/vfio_ap_ops.c
>>>> index bc2b05e..e3ff5ab 100644
>>>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>>>> @@ -53,6 +53,54 @@ static int vfio_ap_mdev_remove(struct 
>>>> mdev_device *mdev)
>>>>       return 0;
>>>>   }
>>>>
>>>> +static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>>>> +                       unsigned long action, void *data)
>>>> +{
>>>> +    struct ap_matrix_mdev *matrix_mdev;
>>>> +
>>>> +    if (action == VFIO_GROUP_NOTIFY_SET_KVM) {
>>>> +        matrix_mdev = container_of(nb, struct ap_matrix_mdev,
>>>> +                       group_notifier);
>>>> +        matrix_mdev->kvm = data;
>>>> +    }
>>>> +
>>>> +    return NOTIFY_OK;
>>>> +}
>>>> +
>>>> +static int vfio_ap_mdev_open(struct mdev_device *mdev)
>>>> +{
>>>> +    struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>>>> +    unsigned long events;
>>>> +    int ret;
>>>> +
>>>> +    matrix_mdev->group_notifier.notifier_call = 
>>>> vfio_ap_mdev_group_notifier;
>>>> +    events = VFIO_GROUP_NOTIFY_SET_KVM;
>>>> +
>>>> +    ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
>>>> +                     &events, &matrix_mdev->group_notifier);
>>>> +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    ret = kvm_ap_interpret_instructions(matrix_mdev->kvm, true);
>>>
>>> Do you need this call ?
>>> apie is always enabled in KVM if AP instructions are available.
>>
>> I suppose we don't, in which case we don't need the 
>> kvm_ap_interpret_instructions()
>> function either ... at least not until we implement interception.
>>
>>>
>>>
>>> Setting or not the interpretation is done for the VM in a all.
>>> It is not the right place to do it here since open is device dependent.
>>
>> As I stated above, at this time we probably do not need this, however;
>> that will not always be the case. The setting is and always will be 
>> for the
>> VM in all - unless the architecture changes - because it is 
>> controlled by a
>> single bit (ECA.28). If you recall, I originally set interpretation 
>> in the
>> vfio_ap device driver when notified of the VFIO_GROUP_NOTIFY_SET_KVM 
>> event.
>> I believe ultimately that it is the device driver that should set the 
>> value
>> for apie.
>>
>>
>>
>>>
>>>
>>> Or we only have one device in the VM at a time.
>>> In this case, shouldn't we make it official by returning -EEXIST for 
>>> the second call?
>>
>> We do allow only one vfio-ap device at a time. QEMU will allow only 
>> one vfio-ap device
>> to be configured for a guest. Should we also put a check in here?
>
> QEMU is not the only possible user of this interface.

True .... I will put a check in here to make sure only one device is 
created.

>
>
>>
>>>
>>>
>>>
>>>> +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    ret = kvm_ap_configure_matrix(matrix_mdev->kvm,
>>>> +                      matrix_mdev->matrix);
>>>> +
>>>> +    return ret;
>>>> +}
>>>> +
>>>> +static void vfio_ap_mdev_release(struct mdev_device *mdev)
>>>> +{
>>>> +    struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>>>> +
>>>> +    kvm_ap_deconfigure_matrix(matrix_mdev->kvm);
>>>> +    kvm_ap_interpret_instructions(matrix_mdev->kvm, false);
>>>
>>> This call clears the apie in KVM.
>>> This is only OK if we have a single device present until the end of 
>>> the VM,
>>> otherwise AP instructions in the guest will fail after the release 
>>> until the end of the VM
>>> or until a new device is plugged.
>>
>> See Message ID: 
>> <1523819244-29954-5-git-send-email-akrowiak@linux.vnet.ibm.com> on the
>> qemu mailing list. There will be only one vfio-ap device allowed for 
>> the MVP model.
>
> dito.
> Anyone can write a userland application using this interface.

See comments above, not to mention I will probably remove this call.

>
> <2b053349-071e-17ed-6ebd-a37bcfd2f330@linux.vnet.ibm.com>
>>
>>>
>>>
>>>
>>>> + vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
>>>> +                 &matrix_mdev->group_notifier);
>>>> +}
>>>> +
>>>>   static ssize_t name_show(struct kobject *kobj, struct device 
>>>> *dev, char *buf)
>>>>   {
>>>>       return sprintf(buf, "%s\n", VFIO_AP_MDEV_NAME_HWVIRT);
>>>> @@ -754,6 +802,8 @@ static ssize_t matrix_show(struct device *dev, 
>>>> struct device_attribute *attr,
>>>>       .mdev_attr_groups    = vfio_ap_mdev_attr_groups,
>>>>       .create            = vfio_ap_mdev_create,
>>>>       .remove            = vfio_ap_mdev_remove,
>>>> +    .open            = vfio_ap_mdev_open,
>>>> +    .release        = vfio_ap_mdev_release,
>>>>   };
>>>>
>>>>   int vfio_ap_mdev_register(struct ap_matrix *ap_matrix)
>>>> diff --git a/drivers/s390/crypto/vfio_ap_private.h 
>>>> b/drivers/s390/crypto/vfio_ap_private.h
>>>> index f248faf..48e2806 100644
>>>> --- a/drivers/s390/crypto/vfio_ap_private.h
>>>> +++ b/drivers/s390/crypto/vfio_ap_private.h
>>>> @@ -31,6 +31,8 @@ struct ap_matrix {
>>>>
>>>>   struct ap_matrix_mdev {
>>>>       struct kvm_ap_matrix *matrix;
>>>> +    struct notifier_block group_notifier;
>>>> +    struct kvm *kvm;
>>>>   };
>>>>
>>>>   static inline struct ap_matrix *to_ap_matrix(struct device *dev)
>>>
>>>
>>
>