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xen-disk: only advertize feature-persistent if grant copy is not available

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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 <paul.durrant@citrix.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
This commit is contained in:
Paul Durrant 2017-06-21 08:52:47 -04:00 committed by Stefano Stabellini
parent b0ac694fdb
commit 976eba1c88
1 changed files with 8 additions and 7 deletions
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15
hw/block/xen_disk.c
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@ -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,