commit 5c81161f804144b146607f890e84613a4cbad95c
author Stefano Garzarella <sgarzare@redhat.com> Thu Feb 21 11:33:07 2019 +0100
committer Stefan Hajnoczi <stefanha@redhat.com> Fri Feb 22 09:42:16 2019 +0000
tree df55db0d4d94ecb8f75a3f62c3e2e789425d2d2b
parent bbe8bd4d85d80442f87774d7bffaca11f2c02b9b

virtio-blk: add "discard" and "write-zeroes" properties

In order to avoid migration issues, we enable DISCARD and
WRITE_ZEROES features only for machine type >= 4.0

As discussed with Michael S. Tsirkin and Stefan Hajnoczi on the
list [1], DISCARD operation should not have security implications
(eg. page cache attacks), so we can enable it by default.

[1] https://lists.gnu.org/archive/html/qemu-devel/2019-02/msg00504.html

Suggested-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20190221103314.58500-4-sgarzare@redhat.com
Message-Id: <20190221103314.58500-4-sgarzare@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/block/virtio-blk.c

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 7813237..f7cd322 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -1027,6 +1027,10 @@
     DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size, 128),
     DEFINE_PROP_LINK("iothread", VirtIOBlock, conf.iothread, TYPE_IOTHREAD,
                      IOThread *),
+    DEFINE_PROP_BIT64("discard", VirtIOBlock, host_features,
+                      VIRTIO_BLK_F_DISCARD, true),
+    DEFINE_PROP_BIT64("write-zeroes", VirtIOBlock, host_features,
+                      VIRTIO_BLK_F_WRITE_ZEROES, true),
     DEFINE_PROP_END_OF_LIST(),
 };