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

Christian Borntraeger
2019-02-19T09:44:25Z

On 19.02.2019 10:22, Cornelia Huck wrote:
> On Mon, 18 Feb 2019 19:08:48 +0100
> Pierre Morel <pmorel@linux.ibm.com> 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
>
> s/suppress/remove/ ?
>
>> 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(-)
>
> (...)
>
>> @@ -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;
>> +}
>
> I don't think you need this (the important function is the match
> function of the bus).

Yes, with

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index 8e45559795429..8ceec41afe322 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -68,15 +68,9 @@ static struct bus_type matrix_bus = {
.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)

on top things still look fine.

>
>> +
>> +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;
>
> It's a bit annoying that we need to introduce a bus that basically does
> nothing, but I think this looks sane.
>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>