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xen-block: support feature-large-sector-size

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A recent Xen commit [1] clarified the semantics of sector based quantities
used in the blkif protocol such that it is now safe to create a xen-block
device with a logical_block_size != 512, as long as the device only
connects to a frontend advertizing 'feature-large-block-size'.

This patch modifies xen-block accordingly. It also uses a stack variable
for the BlockBackend in xen_block_realize() to avoid repeated dereferencing
of the BlockConf pointer, and changes the parameters of
xen_block_dataplane_create() so that the BlockBackend pointer and sector
size are passed expicitly rather than implicitly via the BlockConf.

These modifications have been tested against a recent Windows PV XENVBD
driver [2] using a xen-disk device with a 4kB logical block size.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=67e1c050e36b2c9900cca83618e56189effbad98
[2] https://winpvdrvbuild.xenproject.org:8080/job/XENVBD-master/126

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Message-Id: <20190409164038.25484-1-paul.durrant@citrix.com>
[Edited error message]
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This commit is contained in:
Paul Durrant 2019-04-09 17:40:38 +01:00 • committed by Anthony PERARD
parent 474f3938d7
commit 5feeb718d7
3 changed files with 40 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

38
hw/block/xen-block.c
View file

@ -52,11 +52,25 @@ static void xen_block_connect(XenDevice *xendev, Error **errp)
XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);
const char *type = object_get_typename(OBJECT(blockdev));
XenBlockVdev *vdev = &blockdev->props.vdev;
BlockConf *conf = &blockdev->props.conf;
unsigned int feature_large_sector_size;
unsigned int order, nr_ring_ref, *ring_ref, event_channel, protocol;
char *str;
trace_xen_block_connect(type, vdev->disk, vdev->partition);
if (xen_device_frontend_scanf(xendev, "feature-large-sector-size", "%u",
&feature_large_sector_size) != 1) {
feature_large_sector_size = 0;
}
if (feature_large_sector_size != 1 &&
conf->logical_block_size != XEN_BLKIF_SECTOR_SIZE) {
error_setg(errp, "logical_block_size != %u not supported by frontend",
XEN_BLKIF_SECTOR_SIZE);
return;
}
if (xen_device_frontend_scanf(xendev, "ring-page-order", "%u",
&order) != 1) {
nr_ring_ref = 1;
@ -150,7 +164,7 @@ 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) / XEN_BLKIF_SECTOR_SIZE;
int64_t sectors = blk_getlength(conf->blk) / conf->logical_block_size;
XenDevice *xendev = XEN_DEVICE(blockdev);
trace_xen_block_size(type, vdev->disk, vdev->partition, sectors);
@ -185,6 +199,7 @@ static void xen_block_realize(XenDevice *xendev, Error **errp)
const char *type = object_get_typename(OBJECT(blockdev));
XenBlockVdev *vdev = &blockdev->props.vdev;
BlockConf *conf = &blockdev->props.conf;
BlockBackend *blk = conf->blk;
Error *local_err = NULL;
if (vdev->type == XEN_BLOCK_VDEV_TYPE_INVALID) {
@ -206,8 +221,8 @@ static void xen_block_realize(XenDevice *xendev, Error **errp)
* The blkif protocol does not deal with removable media, so it must
* always be present, even for CDRom devices.
*/
assert(conf->blk);
if (!blk_is_inserted(conf->blk)) {
assert(blk);
if (!blk_is_inserted(blk)) {
error_setg(errp, "device needs media, but drive is empty");
return;
}
@ -224,26 +239,20 @@ 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");
return;
}
blk_set_dev_ops(conf->blk, &xen_block_dev_ops, blockdev);
blk_set_guest_block_size(conf->blk, conf->logical_block_size);
blk_set_dev_ops(blk, &xen_block_dev_ops, blockdev);
blk_set_guest_block_size(blk, conf->logical_block_size);
if (conf->discard_granularity == -1) {
conf->discard_granularity = conf->physical_block_size;
}
if (blk_get_flags(conf->blk) & BDRV_O_UNMAP) {
if (blk_get_flags(blk) & BDRV_O_UNMAP) {
xen_device_backend_printf(xendev, "feature-discard", "%u", 1);
xen_device_backend_printf(xendev, "discard-granularity", "%u",
conf->discard_granularity);
@ -260,12 +269,13 @@ static void xen_block_realize(XenDevice *xendev, Error **errp)
blockdev->device_type);
xen_device_backend_printf(xendev, "sector-size", "%u",
XEN_BLKIF_SECTOR_SIZE);
conf->logical_block_size);
xen_block_set_size(blockdev);
blockdev->dataplane =
xen_block_dataplane_create(xendev, conf, blockdev->props.iothread);
xen_block_dataplane_create(xendev, blk, conf->logical_block_size,
blockdev->props.iothread);
}
static void xen_block_frontend_changed(XenDevice *xendev,