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vhost-vdpa: Set discarding of RAM broken when initializing the backend 

Similar to VFIO, vDPA will go ahead an map+pin all guest memory. Memory
that used to be discarded will get re-populated and if we
discard+re-access memory after mapping+pinning, the pages mapped into the
vDPA IOMMU will go out of sync with the actual pages mapped into the user
space page tables.

Set discarding of RAM broken such that:
- virtio-mem and vhost-vdpa run mutually exclusive
- virtio-balloon is inhibited and no memory discards will get issued

In the future, we might be able to support coordinated discarding of RAM
as used by virtio-mem and already supported by vfio via the
RamDiscardManager.

Acked-by: Jason Wang <jasowang@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Cindy Lu <lulu@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20211027130324.59791-1-david@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
This commit is contained in:
David Hildenbrand 2021-10-27 15:03:24 +02:00 committed by Michael S. Tsirkin
parent 44d3d89814
commit e1c1915bef
1 changed files with 13 additions and 0 deletions
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13
hw/virtio/vhost-vdpa.c
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@ -331,6 +331,17 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
struct vhost_vdpa *v;
assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
trace_vhost_vdpa_init(dev, opaque);
int ret;
/*
* Similar to VFIO, we end up pinning all guest memory and have to
* disable discarding of RAM.
*/
ret = ram_block_discard_disable(true);
if (ret) {
error_report("Cannot set discarding of RAM broken");
return ret;
}
v = opaque;
v->dev = dev;
@ -442,6 +453,8 @@ static int vhost_vdpa_cleanup(struct vhost_dev *dev)
memory_listener_unregister(&v->listener);
dev->opaque = NULL;
ram_block_discard_disable(false);
return 0;
}