From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 20 Feb 2019 13:51:08 +0100 From: Halil Pasic Subject: Re: [PATCH v2 1/1] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem In-Reply-To: <20190220102731.4fca4f91.cohuck@redhat.com> References: <1550513328-12646-1-git-send-email-pmorel@linux.ibm.com> <1550513328-12646-2-git-send-email-pmorel@linux.ibm.com> <8e6853ba-12ed-a4f3-1263-0e15f715b644@linux.ibm.com> <6cc5b478-4678-9a82-b902-cc9aed22becf@linux.ibm.com> <20190220102731.4fca4f91.cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20190220135108.49f8f891@oc2783563651> Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Cornelia Huck Cc: Pierre Morel , Tony Krowiak , borntraeger@de.ibm.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com List-ID: On Wed, 20 Feb 2019 10:27:31 +0100 Cornelia Huck wrote: > On Tue, 19 Feb 2019 22:31:17 +0100 > Pierre Morel wrote: > > > On 19/02/2019 19:52, Tony Krowiak wrote: > > > On 2/18/19 1:08 PM, 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 > > >> Reported-by: Christian Borntraeger > > >> Signed-off-by: Pierre Morel > > >> --- > > >>   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; > > > > > > I think we should verify the following: > > > > > > * dev == matrix_dev->device > > > * drv == &matrix_driver > > > > > > The model employed is for the matrix device to be a singleton, so I > > > think we should verify that the matrix device and driver defined herein > > > ought to be the only possible choices for a match. Of course, doing so > > > will require some restructuring of this patch. > > > > I think Conny already answered this question. > > Not quite :), but I don't think we need any magic in there, as there's > only one device and only one driver on that bus. No need to make this > more complicated. > I agree, no need to complicate this any further. > > > > > > > >> +} > > >> + > > >> +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", > > > > > > This is the same name used for the original device driver. I think > > > this driver ought to have a different name to avoid confusion. > > > How about vfio_ap_matrix or some other name to differentiate the > > > two. > > > > I would like too, but changing this will change the path to the mediated > > device supported type. > > Yes, we don't want to change that. > Nod. > > > > > > > > > >> +    .bus = &matrix_bus, > > >> +    .probe = matrix_probe, > > > > > > I would add: > > >     .suppress_bind_attrs = true; > > > > > > This will remove the sysfs bind/unbind interfaces. Since there is only > > > one matrix device and it's lifecycle is controlled herein, there is no > > > sense in allowing a root user to bind/unbind it. > > > > > > > OTOH bind/unbind has no impact. > > If no one else ask for this I will not change what has already been > > reviewed by Conny and Christian. > > As we only have one driver, it does not really make sense anyway. > I see this as a reason to suppress_bind_attrs. It is much easier than to think about what should happen when one unbinds the matrix device from the vfio_ap driver on the vfio_ap bus. With the code as is it seems to just keep working as if nothing happened. And /sys/devices/vfio_ap/matrix/mdev_supported_types/ referencing the name of the driver that is already gone sounds a bit weird. Regards, Halil