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Date:   Tue, 15 Dec 2020 18:42:34 +0100
From:   Cornelia Huck <>
To:     Tony Krowiak <>
Subject: Re: [PATCH v3] s390/vfio-ap: clean up vfio_ap resources when KVM
 pointer invalidated

On Mon, 14 Dec 2020 11:56:17 -0500
Tony Krowiak <> wrote:

> The vfio_ap device driver registers a group notifier with VFIO when the
> file descriptor for a VFIO mediated device for a KVM guest is opened to
> receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM
> event). When the KVM pointer is set, the vfio_ap driver takes the
> following actions:
> 1. Stashes the KVM pointer in the vfio_ap_mdev struct that holds the state
>    of the mediated device.
> 2. Calls the kvm_get_kvm() function to increment its reference counter.
> 3. Sets the function pointer to the function that handles interception of
>    the instruction that enables/disables interrupt processing.
> 4. Sets the masks in the KVM guest's CRYCB to pass AP resources through to
>    the guest.
> In order to avoid memory leaks, when the notifier is called to receive
> notification that the KVM pointer has been set to NULL, the vfio_ap device
> driver should reverse the actions taken when the KVM pointer was set.
> Fixes: 258287c994de ("s390: vfio-ap: implement mediated device open callback")
> Signed-off-by: Tony Krowiak <>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)

Reviewed-by: Cornelia Huck <>

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