Re: [PATCH v2 1/1] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem

Harald Freudenberger
2019-02-21T08:07:35Z

On 21.02.19 08:37, Christian Borntraeger wrote:
>
> On 20.02.2019 14:12, Harald Freudenberger wrote:
>> On 18.02.19 19:08, Pierre Morel wrote:
>>> Libudev relies on having a subsystem link for non-root devices. To
>>> avoid libudev (and potentially other userspace tools) choking on the
>>> matrix device let us introduce a vfio_ap bus and with that the vfio_ap
>>> bus subsytem, and make the matrix device reside within it.
>>>
>>> Doing this we need to suppress the forced link from the matrix device to
>>> the vfio_ap driver and we suppress the device_type we do not need
>>> anymore.
>>>
>>> Since the associated matrix driver is not the vfio_ap driver any more,
>>> we have to change the search for the devices on the vfio_ap driver in
>>> the function vfio_ap_verify_queue_reserved.
>>>
>>> Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
>>> Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>>> ---
>>> drivers/s390/crypto/vfio_ap_drv.c | 48 +++++++++++++++++++++++++++++------
>>> drivers/s390/crypto/vfio_ap_ops.c | 4 +--
>>> drivers/s390/crypto/vfio_ap_private.h | 1 +
>>> 3 files changed, 43 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
>>> index 31c6c84..8e45559 100644
>>> --- a/drivers/s390/crypto/vfio_ap_drv.c
>>> +++ b/drivers/s390/crypto/vfio_ap_drv.c
>>> @@ -24,10 +24,6 @@ MODULE_LICENSE("GPL v2");
>>>
>>> static struct ap_driver vfio_ap_drv;
>>>
>>> -static struct device_type vfio_ap_dev_type = {
>>> - .name = VFIO_AP_DEV_TYPE_NAME,
>>> -};
>>> -
>>> struct ap_matrix_dev *matrix_dev;
>>>
>>> /* Only type 10 adapters (CEX4 and later) are supported
>>> @@ -62,6 +58,27 @@ static void vfio_ap_matrix_dev_release(struct device *dev)
>>> kfree(matrix_dev);
>>> }
>>>
>>> +static int matrix_bus_match(struct device *dev, struct device_driver *drv)
>>> +{
>>> + return 1;
>>> +}
>>> +
>>> +static struct bus_type matrix_bus = {
>>> + .name = "vfio_ap",
>>> + .match = &matrix_bus_match,
>>> +};
>>> +
>>> +static int matrix_probe(struct device *dev)
>>> +{
>>> + return 0;
>>> +}
>>> +
>>> +static struct device_driver matrix_driver = {
>>> + .name = "vfio_ap",
>>> + .bus = &matrix_bus,
>>> + .probe = matrix_probe,
>>> +};
>>> +
>>> static int vfio_ap_matrix_dev_create(void)
>>> {
>>> int ret;
>>> @@ -71,6 +88,10 @@ static int vfio_ap_matrix_dev_create(void)
>>> if (IS_ERR(root_device))
>>> return PTR_ERR(root_device);
>>>
>>> + ret = bus_register(&matrix_bus);
>>> + if (ret)
>>> + goto bus_register_err;
>>> +
>>> matrix_dev = kzalloc(sizeof(*matrix_dev), GFP_KERNEL);
>>> if (!matrix_dev) {
>>> ret = -ENOMEM;
>>> @@ -87,30 +108,41 @@ static int vfio_ap_matrix_dev_create(void)
>>> mutex_init(&matrix_dev->lock);
>>> INIT_LIST_HEAD(&matrix_dev->mdev_list);
>>>
>>> - matrix_dev->device.type = &vfio_ap_dev_type;
>>> dev_set_name(&matrix_dev->device, "%s", VFIO_AP_DEV_NAME);
>>> matrix_dev->device.parent = root_device;
>>> + matrix_dev->device.bus = &matrix_bus;
>>> matrix_dev->device.release = vfio_ap_matrix_dev_release;
>>> - matrix_dev->device.driver = &vfio_ap_drv.driver;
>>> + matrix_dev->vfio_ap_drv = &vfio_ap_drv;
>>>
>>> ret = device_register(&matrix_dev->device);
>>> if (ret)
>>> goto matrix_reg_err;
>>>
>>> + ret = driver_register(&matrix_driver);
>>> + if (ret)
>>> + goto matrix_drv_err;
>>> +
>>> return 0;
>>>
>>> +matrix_drv_err:
>>> + device_unregister(&matrix_dev->device);
>>> matrix_reg_err:
>>> put_device(&matrix_dev->device);
>>> matrix_alloc_err:
>>> + bus_unregister(&matrix_bus);
>>> +bus_register_err:
>>> root_device_unregister(root_device);
>>> -
>>> return ret;
>>> }
>>>
>>> static void vfio_ap_matrix_dev_destroy(void)
>>> {
>>> + struct device *root_device = matrix_dev->device.parent;
>>> +
>>> + driver_unregister(&matrix_driver);
>>> device_unregister(&matrix_dev->device);
>>> - root_device_unregister(matrix_dev->device.parent);
>>> + bus_unregister(&matrix_bus);
>>> + root_device_unregister(root_device);
>>> }
>>>
>>> static int __init vfio_ap_init(void)
>>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>>> index 272ef42..900b9cf 100644
>>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>>> @@ -198,8 +198,8 @@ static int vfio_ap_verify_queue_reserved(unsigned long *apid,
>>> qres.apqi = apqi;
>>> qres.reserved = false;
>>>
>>> - ret = driver_for_each_device(matrix_dev->device.driver, NULL, &qres,
>>> - vfio_ap_has_queue);
>>> + ret = driver_for_each_device(&matrix_dev->vfio_ap_drv->driver, NULL,
>>> + &qres, vfio_ap_has_queue);
>>> if (ret)
>>> return ret;
>>>
>>> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
>>> index 5675492..76b7f98 100644
>>> --- a/drivers/s390/crypto/vfio_ap_private.h
>>> +++ b/drivers/s390/crypto/vfio_ap_private.h
>>> @@ -40,6 +40,7 @@ struct ap_matrix_dev {
>>> struct ap_config_info info;
>>> struct list_head mdev_list;
>>> struct mutex lock;
>>> + struct ap_driver *vfio_ap_drv;
>>> };
>>>
>>> extern struct ap_matrix_dev *matrix_dev;
>> You are introducing a new bus just for a user space application which is unable
>> to deal with a device directly attached to the root of devices ? So you are fixing
>> kernel code because of disability of userspace code. Hm, you are switching
>> root cause and effect. However, not my job.
> the kernel rule is pretty simple. If userspace breaks due to a kernel change fix the
> kernel.
>
>> Why do you need this dummy bus ? Did you evaluate using a "class" subsystem
>> instead ? This is very common and my assumption is that libudev is able to handle
>> this. I am using a "zcrypt" class for providing additional zcrypt device nodes and
>> this works fine together with udev. I would avoid the introduction and maintenance
>> of bus code at any cost.
> The class variant sounds promising. Pierre what do you think?
I checked that. My additional zcrypt devices (you can easily create one
with just echo "blubber" >/sys/class/zcrypt/create) and then have a look
to the new device entry in sysfs at /sys/devices/virtual/zcrypt/blubber).
Maybe you need to alloc device numbers for this - I am not sure if it is
sufficient to device_register() without a device number. However, have
a look into zcrpyt_api.c zcdn_init() and zcdn_create().
With a new class, you can also remove the root device needed as an
anchor for the old and for the bus code.
>> Btw. having a look onto the naming ... the module is named "vfio_ap", the
>> driver is named "vfio_ap", the bus is named "vfio_ap", the root bus device is
>> named "vfio_ap" ... a bunch of vfio_aps naming different things.
>>
>> regards
>> Harald Freudenberger
>>