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xen-block: scale sector based quantities correctly

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The Xen blkif protocol requires that sector based quantities should be
interpreted strictly as multiples of 512 bytes. Specifically:

"first_sect and last_sect in blkif_request_segment, as well as
sector_number in blkif_request, are always expressed in 512-byte units."

Commit fcab2b464e "xen: add header and build dataplane/xen-block.c"
incorrectly modified behaviour to use the block device logical_block_size
property as the scale, instead of correctly shifting values by the
hardcoded BDRV_SECTOR_BITS (and hence scaling them to 512 byte units).
This patch undoes that change and restores compliance with the spec.

Furthermore, this patch also restores the original xen_disk behaviour
of advertizing a hardcoded 'sector-size' value of 512 in xenstore and
scaling 'sectors' accordingly. The realize() method is also modified to
fail if logical_block_size is set to anything other than 512.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Message-Id: <20190401121719.27208-1-paul.durrant@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This commit is contained in:
Paul Durrant 2019-04-01 13:17:19 +01:00 • committed by Anthony PERARD
parent 15f084505a
commit 2bcd05cf24
3 changed files with 23 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

10
hw/block/xen-block.c
View file

@ -149,7 +149,7 @@ static void xen_block_set_size(XenBlockDevice *blockdev)
const char *type = object_get_typename(OBJECT(blockdev));
XenBlockVdev *vdev = &blockdev->props.vdev;
BlockConf *conf = &blockdev->props.conf;
int64_t sectors = blk_getlength(conf->blk) / conf->logical_block_size;
int64_t sectors = blk_getlength(conf->blk) / XEN_BLKIF_SECTOR_SIZE;
XenDevice *xendev = XEN_DEVICE(blockdev);
trace_xen_block_size(type, vdev->disk, vdev->partition, sectors);
@ -223,6 +223,12 @@ static void xen_block_realize(XenDevice *xendev, Error **errp)
blkconf_blocksizes(conf);
if (conf->logical_block_size != XEN_BLKIF_SECTOR_SIZE) {
error_setg(errp, "logical_block_size != %u not supported",
XEN_BLKIF_SECTOR_SIZE);
return;
}
if (conf->logical_block_size > conf->physical_block_size) {
error_setg(
errp, "logical_block_size > physical_block_size not supported");
@ -253,7 +259,7 @@ static void xen_block_realize(XenDevice *xendev, Error **errp)
blockdev->device_type);
xen_device_backend_printf(xendev, "sector-size", "%u",
conf->logical_block_size);
XEN_BLKIF_SECTOR_SIZE);
xen_block_set_size(blockdev);