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

[Cornelia Huck <cohuck@redhat.com>]

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?

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