From e1c1915befbd2a991b20812eef6ad650b5637a36 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Wed, 27 Oct 2021 15:03:24 +0200 Subject: 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 Cc: Jason Wang Cc: Michael S. Tsirkin Cc: Cindy Lu Signed-off-by: David Hildenbrand Message-Id: <20211027130324.59791-1-david@redhat.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefano Garzarella --- hw/virtio/vhost-vdpa.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c index 12661fd..0d80514 100644 --- a/hw/virtio/vhost-vdpa.c +++ b/hw/virtio/vhost-vdpa.c @@ -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; } -- cgit v1.1