From fb0b154c801e3447e505de420195fb7038695941 Mon Sep 17 00:00:00 2001
From: Akihiko Odaki
Date: Thu, 25 Feb 2021 09:12:39 +0900
Subject: virtio-blk: Respect discard granularity

Report the configured granularity for discard operation to the
guest. If this is not set use the block size.

Since until now we have ignored the configured discard granularity
and always reported the block size, let's add
'report-discard-granularity' property and disable it for older
machine types to avoid migration issues.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210225001239.47046-1-akihiko.odaki@gmail.com>
---
 hw/block/virtio-blk.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'hw/block')

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 3d2072cf75..d28979efb8 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,
-- 
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