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    SubjectRe: [PATCH v12 12/22] vfio: Add notifier callback to parent's ops structure of mdev
    On 11/15/2016 04:11 PM, Kirti Wankhede wrote:
    >
    >
    > On 11/15/2016 12:15 PM, Jike Song wrote:
    >> On 11/14/2016 11:42 PM, Kirti Wankhede wrote:
    >>> Add a notifier calback to parent's ops structure of mdev device so that per
    >>> device notifer for vfio module is registered through vfio_mdev module.
    >>>
    >>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
    >>> Signed-off-by: Neo Jia <cjia@nvidia.com>
    >>> Change-Id: Iafa6f1721aecdd6e50eb93b153b5621e6d29b637
    >>> ---
    >>> drivers/vfio/mdev/vfio_mdev.c | 19 +++++++++++++++++++
    >>> include/linux/mdev.h | 9 +++++++++
    >>> 2 files changed, 28 insertions(+)
    >>>
    >>> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
    >>> index ffc36758cb84..1694b1635607 100644
    >>> --- a/drivers/vfio/mdev/vfio_mdev.c
    >>> +++ b/drivers/vfio/mdev/vfio_mdev.c
    >>> @@ -24,6 +24,15 @@
    >>> #define DRIVER_AUTHOR "NVIDIA Corporation"
    >>> #define DRIVER_DESC "VFIO based driver for Mediated device"
    >>>
    >>> +static int vfio_mdev_notifier(struct notifier_block *nb, unsigned long action,
    >>> + void *data)
    >>> +{
    >>> + struct mdev_device *mdev = container_of(nb, struct mdev_device, nb);
    >>> + struct parent_device *parent = mdev->parent;
    >>> +
    >>> + return parent->ops->notifier(mdev, action, data);
    >>> +}
    >>> +
    >>> static int vfio_mdev_open(void *device_data)
    >>> {
    >>> struct mdev_device *mdev = device_data;
    >>> @@ -40,6 +49,11 @@ static int vfio_mdev_open(void *device_data)
    >>> if (ret)
    >>> module_put(THIS_MODULE);
    >>>
    >>> + if (likely(parent->ops->notifier)) {
    >>> + mdev->nb.notifier_call = vfio_mdev_notifier;
    >>> + if (vfio_register_notifier(&mdev->dev, &mdev->nb))
    >>> + pr_err("Failed to register notifier for mdev\n");
    >>> + }
    >>
    >> Hi Kirti,
    >>
    >> Could you please move the notifier registration before parent->ops->open()?
    >> as you might know, I'm extending your vfio_register_notifier to also include
    >> the attaching/detaching events of vfio_group and kvm. Basically if vfio_group
    >> not attached to any kvm instance, the parent->ops->open() should return -ENODEV
    >> to indicate the failure, but to know whether kvm is available in open(), the
    >> notifier registration should be earlier.
    >>
    >
    > Ok. That seem fine to me.
    >

    Thanks - and I guess it's also good to move unregister after ->release(),
    so that a sequence of register-open-release-unregister guaranteed :)

    --
    Thanks,
    Jike

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