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authorPaul Durrant <pdurrant@amazon.com>2019-12-11 15:29:56 +0000
committerJuergen Gross <jgross@suse.com>2019-12-20 13:44:45 +0100
commitf4eef1b652eeb850a0f44e8f985cc4153a0c0265 (patch)
tree7e3ac85060e8a9e29ba590743eb6161ecf099e4e /drivers/block
parent1ee54195a305fae3955642af8528bdf67496d353 (diff)
xen-blkback: support dynamic unbind/bind
By simply re-attaching to shared rings during connect_ring() rather than assuming they are freshly allocated (i.e assuming the counters are zero) it is possible for vbd instances to be unbound and re-bound from and to (respectively) a running guest. This has been tested by running: while true; do fio --name=randwrite --ioengine=libaio --iodepth=16 \ --rw=randwrite --bs=4k --direct=1 --size=1G --verify=crc32; done in a PV guest whilst running: while true; do echo vbd-$DOMID-$VBD >unbind; echo unbound; sleep 5; echo vbd-$DOMID-$VBD >bind; echo bound; sleep 3; done in dom0 from /sys/bus/xen-backend/drivers/vbd to continuously unbind and re-bind its system disk image. This is a highly useful feature for a backend module as it allows it to be unloaded and re-loaded (i.e. updated) without requiring domUs to be halted. This was also tested by running: while true; do echo vbd-$DOMID-$VBD >unbind; echo unbound; sleep 5; rmmod xen-blkback; echo unloaded; sleep 1; modprobe xen-blkback; echo bound; cd $(pwd); sleep 3; done in dom0 whilst running the same loop as above in the (single) PV guest. Some (less stressful) testing has also been done using a Windows HVM guest with the latest 9.0 PV drivers installed. Signed-off-by: Paul Durrant <pdurrant@amazon.com> Reviewed-by: Juergen Gross <jgross@suse.com> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/xen-blkback/xenbus.c56
1 files changed, 38 insertions, 18 deletions
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index d6a6adfd5159..4c5d99f87813 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -190,6 +190,9 @@ static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
{
int err;
struct xen_blkif *blkif = ring->blkif;
+ const struct blkif_common_sring *sring_common;
+ RING_IDX rsp_prod, req_prod;
+ unsigned int size;
/* Already connected through? */
if (ring->irq)
@@ -200,46 +203,62 @@ static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
if (err < 0)
return err;
+ sring_common = (struct blkif_common_sring *)ring->blk_ring;
+ rsp_prod = READ_ONCE(sring_common->rsp_prod);
+ req_prod = READ_ONCE(sring_common->req_prod);
+
switch (blkif->blk_protocol) {
case BLKIF_PROTOCOL_NATIVE:
{
- struct blkif_sring *sring;
- sring = (struct blkif_sring *)ring->blk_ring;
- BACK_RING_INIT(&ring->blk_rings.native, sring,
- XEN_PAGE_SIZE * nr_grefs);
+ struct blkif_sring *sring_native =
+ (struct blkif_sring *)ring->blk_ring;
+
+ BACK_RING_ATTACH(&ring->blk_rings.native, sring_native,
+ rsp_prod, XEN_PAGE_SIZE * nr_grefs);
+ size = __RING_SIZE(sring_native, XEN_PAGE_SIZE * nr_grefs);
break;
}
case BLKIF_PROTOCOL_X86_32:
{
- struct blkif_x86_32_sring *sring_x86_32;
- sring_x86_32 = (struct blkif_x86_32_sring *)ring->blk_ring;
- BACK_RING_INIT(&ring->blk_rings.x86_32, sring_x86_32,
- XEN_PAGE_SIZE * nr_grefs);
+ struct blkif_x86_32_sring *sring_x86_32 =
+ (struct blkif_x86_32_sring *)ring->blk_ring;
+
+ BACK_RING_ATTACH(&ring->blk_rings.x86_32, sring_x86_32,
+ rsp_prod, XEN_PAGE_SIZE * nr_grefs);
+ size = __RING_SIZE(sring_x86_32, XEN_PAGE_SIZE * nr_grefs);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
- struct blkif_x86_64_sring *sring_x86_64;
- sring_x86_64 = (struct blkif_x86_64_sring *)ring->blk_ring;
- BACK_RING_INIT(&ring->blk_rings.x86_64, sring_x86_64,
- XEN_PAGE_SIZE * nr_grefs);
+ struct blkif_x86_64_sring *sring_x86_64 =
+ (struct blkif_x86_64_sring *)ring->blk_ring;
+
+ BACK_RING_ATTACH(&ring->blk_rings.x86_64, sring_x86_64,
+ rsp_prod, XEN_PAGE_SIZE * nr_grefs);
+ size = __RING_SIZE(sring_x86_64, XEN_PAGE_SIZE * nr_grefs);
break;
}
default:
BUG();
}
+ err = -EIO;
+ if (req_prod - rsp_prod > size)
+ goto fail;
+
err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
xen_blkif_be_int, 0,
"blkif-backend", ring);
- if (err < 0) {
- xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
- ring->blk_rings.common.sring = NULL;
- return err;
- }
+ if (err < 0)
+ goto fail;
ring->irq = err;
return 0;
+
+fail:
+ xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
+ ring->blk_rings.common.sring = NULL;
+ return err;
}
static int xen_blkif_disconnect(struct xen_blkif *blkif)
@@ -1131,7 +1150,8 @@ static struct xenbus_driver xen_blkbk_driver = {
.ids = xen_blkbk_ids,
.probe = xen_blkbk_probe,
.remove = xen_blkbk_remove,
- .otherend_changed = frontend_changed
+ .otherend_changed = frontend_changed,
+ .allow_rebind = true,
};
int xen_blkif_xenbus_init(void)