Messages in this thread | | | Subject | Re: [PATCH v5 05/13] s390: vfio-ap: register matrix device with VFIO mdev framework | From | Pierre Morel <> | Date | Tue, 15 May 2018 16:17:01 +0200 |
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On 14/05/2018 21:42, Tony Krowiak wrote: > On 05/11/2018 01:18 PM, Halil Pasic wrote: >> >> >> On 05/07/2018 05:11 PM, Tony Krowiak wrote: >>> Registers the matrix device created by the VFIO AP device >>> driver with the VFIO mediated device framework. >>> Registering the matrix device will create the sysfs >>> structures needed to create mediated matrix devices >>> each of which will be used to configure the AP matrix >>> for a guest and connect it to the VFIO AP device driver. >>> >> [..] >>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c >>> b/drivers/s390/crypto/vfio_ap_ops.c >>> new file mode 100644 >>> index 0000000..d7d36fb >>> --- /dev/null >>> +++ b/drivers/s390/crypto/vfio_ap_ops.c >>> @@ -0,0 +1,106 @@ >>> +// SPDX-License-Identifier: GPL-2.0+ >>> +/* >>> + * Adjunct processor matrix VFIO device driver callbacks. >>> + * >>> + * Copyright IBM Corp. 2017 >>> + * Author(s): Tony Krowiak <akrowiak@linux.vnet.ibm.com> >>> + * >>> + */ >>> +#include <linux/string.h> >>> +#include <linux/vfio.h> >>> +#include <linux/device.h> >>> +#include <linux/list.h> >>> +#include <linux/ctype.h> >>> + >>> +#include "vfio_ap_private.h" >>> + >>> +#define VFOP_AP_MDEV_TYPE_HWVIRT "passthrough" >>> +#define VFIO_AP_MDEV_NAME_HWVIRT "VFIO AP Passthrough Device" >>> + >>> +static int vfio_ap_mdev_create(struct kobject *kobj, struct >>> mdev_device *mdev) >>> +{ >>> + struct ap_matrix *ap_matrix = to_ap_matrix(mdev_parent_dev(mdev)); >>> + >>> + ap_matrix->available_instances--; >>> + >>> + return 0; >>> +} >>> + >>> +static int vfio_ap_mdev_remove(struct mdev_device *mdev) >>> +{ >>> + struct ap_matrix *ap_matrix = to_ap_matrix(mdev_parent_dev(mdev)); >>> + >>> + ap_matrix->available_instances++; >>> + >>> + return 0; >>> +} >>> + >> >> The above functions seem to be called with the lock of this >> auto-generated >> mdev parent device held. That's why we don't have to care about >> synchronization >> ourselves, right? > > I would assume as much. The comments for the 'struct mdev_parent_ops' in > include/linux/mdev.h do not mention anything about synchronization, > nor did I > see any locking or synchronization in the vfio_ccw implementation > after which > I modeled my code, so frankly it is something I did not consider. > >> >> >> A small comment in the code could be helpful for mdev non-experts. >> Hell, I would >> even consider documenting it for all mdev -- took me some time to >> figure out. > > You may want to bring this up with the VFIO mdev maintainers, but I'd > be happy to > include a comment in the functions in question if you think it important. > >> >> >> [..] >> >> >>> +int vfio_ap_mdev_register(struct ap_matrix *ap_matrix) >>> +{ >>> + int ret; >>> + >>> + ret = mdev_register_device(&ap_matrix->device, >>> &vfio_ap_matrix_ops); >>> + if (ret) >>> + return ret; >>> + >>> + ap_matrix->available_instances = >>> AP_MATRIX_MAX_AVAILABLE_INSTANCES; >>> + >>> + return 0; >>> +} >>> + >>> +void vfio_ap_mdev_unregister(struct ap_matrix *ap_matrix) >>> +{ >>> + ap_matrix->available_instances--; >> >> What is this for? I don't understand. > > To control the number of mediated devices one can create for the > matrix device. > Once the max is reached, the mdev framework will not allow creation of > another > mediated device until one is removed. This counter keeps track of the > number > of instances that can be created. This is documented with the mediated > framework. You may want to take a look at: > > Documentation/vfio-mediated-device.txt > Documentation/vfio.txt > Documentation/virtual/kvm/devices/vfio.txt
This is what you do in create/remove. But here in unregister I agree with Halil, it does not seem to be usefull.
> >> >> >> Regards, >> Halil >> >>> + mdev_unregister_device(&ap_matrix->device); >>> +} > >
-- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany
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