[Qemu-block] [PATCH v2 2/5] virtio-blk: add "discard-wzeroes" boolean property

[Stefano Garzarella]

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

Suggested-by: Dr. David Alan Gilbert <address@hidden>
Signed-off-by: Stefano Garzarella <address@hidden>
---
 hw/block/virtio-blk.c          | 2 ++
 hw/core/machine.c              | 1 +
 include/hw/virtio/virtio-blk.h | 1 +
 3 files changed, 4 insertions(+)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 8a6754d9a2..542ec52536 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -1026,6 +1026,8 @@ 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_BIT("discard-wzeroes", VirtIOBlock, conf.discard_wzeroes, 0,
+                     true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 2629515363..ce98857af0 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -30,6 +30,7 @@ GlobalProperty hw_compat_3_1[] = {
     { "memory-backend-memfd", "x-use-canonical-path-for-ramblock-id", "true" },
     { "tpm-crb", "ppi", "false" },
     { "tpm-tis", "ppi", "false" },
+    { "virtio-blk-device", "discard-wzeroes", "false" },
 };
 const size_t hw_compat_3_1_len = G_N_ELEMENTS(hw_compat_3_1);
 
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index 5117431d96..c336afb4cd 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -40,6 +40,7 @@ struct VirtIOBlkConf
     uint32_t request_merging;
     uint16_t num_queues;
     uint16_t queue_size;
+    uint32_t discard_wzeroes;
 };
 
 struct VirtIOBlockDataPlane;
-- 
2.20.1