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[Qemu-devel] [PULL 2/3] xen-disk: only advertize feature-persistent if g
From: |
Stefano Stabellini |
Subject: |
[Qemu-devel] [PULL 2/3] xen-disk: only advertize feature-persistent if grant copy is not available |
Date: |
Tue, 27 Jun 2017 15:04:42 -0700 |
From: Paul Durrant <address@hidden>
If grant copy is available then it will always be used in preference to
persistent maps. In this case feature-persistent should not be advertized
to the frontend, otherwise it may needlessly copy data into persistently
granted buffers.
Signed-off-by: Paul Durrant <address@hidden>
Signed-off-by: Stefano Stabellini <address@hidden>
Reviewed-by: Stefano Stabellini <address@hidden>
---
hw/block/xen_disk.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 9200511..8218741 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -1022,11 +1022,18 @@ static int blk_init(struct XenDevice *xendev)
blkdev->file_blk = BLOCK_SIZE;
+ blkdev->feature_grant_copy =
+ (xengnttab_grant_copy(blkdev->xendev.gnttabdev, 0, NULL) == 0);
+
+ xen_pv_printf(&blkdev->xendev, 3, "grant copy operation %s\n",
+ blkdev->feature_grant_copy ? "enabled" : "disabled");
+
/* fill info
* blk_connect supplies sector-size and sectors
*/
xenstore_write_be_int(&blkdev->xendev, "feature-flush-cache", 1);
- xenstore_write_be_int(&blkdev->xendev, "feature-persistent", 1);
+ xenstore_write_be_int(&blkdev->xendev, "feature-persistent",
+ !blkdev->feature_grant_copy);
xenstore_write_be_int(&blkdev->xendev, "info", info);
blk_parse_discard(blkdev);
@@ -1201,12 +1208,6 @@ static int blk_connect(struct XenDevice *xendev)
xen_be_bind_evtchn(&blkdev->xendev);
- blkdev->feature_grant_copy =
- (xengnttab_grant_copy(blkdev->xendev.gnttabdev, 0, NULL) == 0);
-
- xen_pv_printf(&blkdev->xendev, 3, "grant copy operation %s\n",
- blkdev->feature_grant_copy ? "enabled" : "disabled");
-
xen_pv_printf(&blkdev->xendev, 1, "ok: proto %s, ring-ref %d, "
"remote port %d, local port %d\n",
blkdev->xendev.protocol, blkdev->ring_ref,
--
1.9.1