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


From: Cornelia Huck
Subject: Re: [Qemu-devel] [PATCH v4 4/5] s390x/vfio: ap: Introduce VFIO AP device
Date: Thu, 19 Apr 2018 14:03:45 +0200

On Sun, 15 Apr 2018 15:07:23 -0400
Tony Krowiak <address@hidden> 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 <address@hidden>
> ---
>  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?

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



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