On 05.12.2018 15:51, Cornelia Huck wrote:
> vfio-ap devices do not pin any pages in the host. Therefore, they
> are belived to be compatible with memory ballooning.
>
> Flag them as compatible, so both vfio-ap and a balloon can be
> used simultaneously.
>
> Signed-off-by: Cornelia Huck <coh...@redhat.com>
> ---
>
> As briefly discussed on IRC. RFC as I do not have easy access to
> hardware I can test this with.
Acked-by: Christian Borntraeger <borntrae...@de.ibm.com>
vfio-ap is based on the SIE support for AP, which transparently handles host
paging.
S390_AP_IOMMU has an empty iommu_ops set and the hardware can tolerate invalid
page
table entries.
So this makes sense to me.
>
> ---
> hw/vfio/ap.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
> index 65de952f44..3bf48eed28 100644
> --- a/hw/vfio/ap.c
> +++ b/hw/vfio/ap.c
> @@ -104,6 +104,14 @@ static void vfio_ap_realize(DeviceState *dev, Error
> **errp)
> vapdev->vdev.name = g_strdup_printf("%s", mdevid);
> vapdev->vdev.dev = dev;
>
> + /*
> + * vfio-ap devices are believed to operate in a way compatible with
> + * memory ballooning, as no pages are pinned in the host.
> + * This needs to be set before vfio_get_device() for vfio common to
> + * handle the balloon inhibitor.
> + */
> + vapdev->vdev.balloon_allowed = true;
> +
> ret = vfio_get_device(vfio_group, mdevid, &vapdev->vdev, &local_err);
> if (ret) {
> goto out_get_dev_err;
>
