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vfio: Convert to ram_block_discard_disable()

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VFIO is (except devices without a physical IOMMU or some mediated devices)
incompatible with discarding of RAM. The kernel will pin basically all VM
memory. Let's convert to ram_block_discard_disable(), which can now
fail, in contrast to qemu_balloon_inhibit().

Leave "x-balloon-allowed" named as it is for now.

Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Tony Krowiak <akrowiak@linux.ibm.com>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: Eric Farman <farman@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20200626072248.78761-4-david@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
David Hildenbrand 2020-06-26 09:22:30 +02:00 • committed by Michael S. Tsirkin
parent d24f31db3b
commit aff92b8286
5 changed files with 44 additions and 38 deletions
Download patch file Download diff file Expand all files Collapse all files

11
hw/vfio/ccw.c
View file

@ -574,12 +574,13 @@ static void vfio_ccw_get_device(VFIOGroup *group, VFIOCCWDevice *vcdev,
/*
* All vfio-ccw devices are believed to operate in a way compatible with
* memory ballooning, ie. pages pinned in the host are in the current
* working set of the guest driver and therefore never overlap with pages
* available to the guest balloon driver. This needs to be set before
* vfio_get_device() for vfio common to handle the balloon inhibitor.
* discarding of memory in RAM blocks, ie. pages pinned in the host are
* in the current working set of the guest driver and therefore never
* overlap e.g., with pages available to the guest balloon driver. This
* needs to be set before vfio_get_device() for vfio common to handle
* ram_block_discard_disable().
*/
vcdev->vdev.balloon_allowed = true;
vcdev->vdev.ram_block_discard_allowed = true;
if (vfio_get_device(group, vcdev->cdev.mdevid, &vcdev->vdev, errp)) {
goto out_err;