Re: [Qemu-devel] [PATCH v4 4/5] s390x/vfio: ap: Introduce VFIO AP device

[Tony Krowiak <akrowiak@linux.vnet.ibm.com>]

On 04/23/2018 03:00 AM, Cornelia Huck wrote:
> On Sun, 22 Apr 2018 12:05:44 -0400
> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>
>> On 04/19/2018 08:03 AM, Cornelia Huck wrote:
>>> On Sun, 15 Apr 2018 15:07:23 -0400
>>> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>>>   
>>>> Introduces a VFIO based AP device. The device is defined via
>>>> the QEMU command line by specifying:
>>>>
>>>>       -device vfio-ap,sysfsdev=<path-to-mediated-matrix-device>
>>>>
>>>> There may be only one vfio-ap device configured for a guest.
>>>>
>>>> The mediated matrix device is created by the VFIO AP device
>>>> driver by writing a UUID to a sysfs attribute file (see
>>>> docs/vfio-ap.txt). The mediated matrix device will be named
>>>> after the UUID. Symbolic links to the $uuid are created in
>>>> many places, so the path to the mediated matrix device $uuid
>>>> can be specified in any of the following ways:
>>>>
>>>> /sys/devices/vfio_ap/matrix/$uuid
>>>> /sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough/devices/$uuid
>>>> /sys/bus/mdev/devices/$uuid
>>>> /sys/bus/mdev/drivers/vfio_mdev/$uuid
>>>>
>>>> When the vfio-ap device is realized, it acquires and opens the
>>>> VFIO iommu group to which the mediated matrix device is
>>>> bound. This causes a VFIO group notification event to be
>>>> signaled. The vfio_ap device driver's group notification
>>>> handler will get called at which time the device driver
>>>> will configure the the AP devices to which the guest will
>>>> be granted access.
>>>>
>>>> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
>>>> ---
>>>>    default-configs/s390x-softmmu.mak |    1 +
>>>>    hw/vfio/Makefile.objs             |    1 +
>>>>    hw/vfio/ap.c                      |  191 +++++++++++++++++++++++++++++++++++++
>>>>    include/hw/vfio/vfio-common.h     |    1 +
>>>>    4 files changed, 194 insertions(+), 0 deletions(-)
>>>>    create mode 100644 hw/vfio/ap.c
>>>> +static void vfio_ap_realize(DeviceState *dev, Error **errp)
>>>> +{
>>>> +    VFIODevice *vbasedev;
>>>> +    VFIOGroup *vfio_group;
>>>> +    APDevice *apdev = DO_UPCAST(APDevice, parent_obj, dev);
>>>> +    char *mdevid;
>>>> +    Error *local_err = NULL;
>>>> +    int ret;
>>>> +
>>>> +    /*
>>>> +     * Since a guest's matrix is configured in its entirety by the mediated
>>>> +     * matrix device and hot plug is not currently supported, there is no
>>>> +     * need to have more than one vfio-ap device. Check if a vfio-ap device
>>>> +     * has already been defined.
>>>> +     */
>>>> +    if (vfio_apdev) {
>>>> +        error_setg(&local_err, "Only one %s device is allowed",
>>>> +                   VFIO_AP_DEVICE_TYPE);
>>>> +        goto out_err;
>>>> +    }
>>>> +
>>>> +    if (!s390_has_feat(S390_FEAT_AP)) {
>>>> +        error_setg(&local_err, "AP support not enabled");
>>>> +        goto out_err;
>>>> +    }
>>>> +
>>>> +    vfio_apdev = DO_UPCAST(VFIOAPDevice, apdev, apdev);
>>>> +
>>>> +    vfio_group = vfio_ap_get_group(vfio_apdev, &local_err);
>>>> +    if (!vfio_group) {
>>>> +        goto out_err;
>>>> +    }
>>>> +
>>>> +    vfio_apdev->vdev.ops = &vfio_ap_ops;
>>>> +    vfio_apdev->vdev.type = VFIO_DEVICE_TYPE_AP;
>>>> +    mdevid = basename(vfio_apdev->vdev.sysfsdev);
>>>> +    vfio_apdev->vdev.name = g_strdup_printf("%s", mdevid);
>>>> +    vfio_apdev->vdev.dev = dev;
>>>> +    QLIST_FOREACH(vbasedev, &vfio_group->device_list, next) {
>>>> +        if (strcmp(vbasedev->name, vfio_apdev->vdev.name) == 0) {
>>>> +            error_setg(&local_err,
>>>> +                       "%s: AP device %s has already been realized",
>>>> +                       VFIO_AP_DEVICE_TYPE, vfio_apdev->vdev.name);
>>>> +            goto out_device_err;
>>>> +        }
>>>> +    }
>>>> +
>>>> +    ret = vfio_get_device(vfio_group, mdevid, &vfio_apdev->vdev, &local_err);
>>>> +    if (ret) {
>>>> +        goto out_device_err;
>>>> +    }
>>> Don't you need a put somewhere to avoid memory leaks?
>> There is a call to vfio_put_device in the unrealize function.
> I don't think unrealize is called if realize failed, so you need to
> clean up in the error cases?

Very true. I  misinterpreted your point. Yes, I need to clean up
if realize fails.

>
>>>   
>>>> +
>>>> +    return;
>>>> +
>>>> +
>>>> +out_device_err:
>>>> +    vfio_put_group(vfio_group);
>>>> +out_err:
>>>> +    vfio_apdev = NULL;
>>>> +    error_propagate(errp, local_err);
>>>> +}
>>