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>

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 781323775632ca7145cc3b58dd9e0d7e7d9b153d..f7cd32281191bc6de3ba960e8103d62d5d907fff 100644 (file)
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -1027,6 +1027,10 @@ static Property virtio_blk_properties[] = {
     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(),
 };
 

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 077fbd182adfcbbff5367d3be3ee6dcdf88990de..766ca5899dad182cd702e27bbf46a0e660124adf 100644 (file)
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -33,6 +33,8 @@ GlobalProperty hw_compat_3_1[] = {
     { "usb-kbd", "serial", "42" },
     { "usb-mouse", "serial", "42" },
     { "usb-kbd", "serial", "42" },
+    { "virtio-blk-device", "discard", "false" },
+    { "virtio-blk-device", "write-zeroes", "false" },
 };
 const size_t hw_compat_3_1_len = G_N_ELEMENTS(hw_compat_3_1);