[PATCH v3] virtio-blk: Respect discard granularity

[Akihiko Odaki]

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
---
 hw/block/virtio-blk.c          | 8 +++++++-
 hw/core/machine.c              | 4 +++-
 include/hw/virtio/virtio-blk.h | 1 +
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index bac2d6fa2b2..f4378e61182 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -962,10 +962,14 @@ static void virtio_blk_update_config(VirtIODevice *vdev, 
uint8_t *config)
     blkcfg.wce = blk_enable_write_cache(s->blk);
     virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues);
     if (virtio_has_feature(s->host_features, VIRTIO_BLK_F_DISCARD)) {
+        uint32_t discard_granularity = conf->discard_granularity;
+        if (discard_granularity == -1 || !s->conf.report_discard_granularity) {
+            discard_granularity = blk_size;
+        }
         virtio_stl_p(vdev, &blkcfg.max_discard_sectors,
                      s->conf.max_discard_sectors);
         virtio_stl_p(vdev, &blkcfg.discard_sector_alignment,
-                     blk_size >> BDRV_SECTOR_BITS);
+                     discard_granularity >> BDRV_SECTOR_BITS);
         /*
          * We support only one segment per request since multiple segments
          * are not widely used and there are no userspace APIs that allow
@@ -1299,6 +1303,8 @@ static Property virtio_blk_properties[] = {
                      IOThread *),
     DEFINE_PROP_BIT64("discard", VirtIOBlock, host_features,
                       VIRTIO_BLK_F_DISCARD, true),
+    DEFINE_PROP_BOOL("report-discard-granularity", VirtIOBlock,
+                     conf.report_discard_granularity, true),
     DEFINE_PROP_BIT64("write-zeroes", VirtIOBlock, host_features,
                       VIRTIO_BLK_F_WRITE_ZEROES, true),
     DEFINE_PROP_UINT32("max-discard-sectors", VirtIOBlock,
diff --git a/hw/core/machine.c b/hw/core/machine.c
index de3b8f1b318..e4df5797e72 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -33,7 +33,9 @@
 #include "migration/global_state.h"
 #include "migration/vmstate.h"
 
-GlobalProperty hw_compat_5_2[] = {};
+GlobalProperty hw_compat_5_2[] = {
+    { "virtio-blk-device", "report-discard-granularity", "off" },
+};
 const size_t hw_compat_5_2_len = G_N_ELEMENTS(hw_compat_5_2);
 
 GlobalProperty hw_compat_5_1[] = {
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index 214ab748229..29655a406dd 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -41,6 +41,7 @@ struct VirtIOBlkConf
     uint16_t num_queues;
     uint16_t queue_size;
     bool seg_max_adjust;
+    bool report_discard_granularity;
     uint32_t max_discard_sectors;
     uint32_t max_write_zeroes_sectors;
     bool x_enable_wce_if_config_wce;
-- 
2.24.3 (Apple Git-128)