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virtio-scsi: implement BlockDevOps->drained_begin() 

The virtio-scsi Host Bus Adapter provides access to devices on a SCSI
bus. Those SCSI devices typically have a BlockBackend. When the
BlockBackend enters a drained section, the SCSI device must temporarily
stop submitting new I/O requests.

Implement this behavior by temporarily stopping virtio-scsi virtqueue
processing when one of the SCSI devices enters a drained section. The
new scsi_device_drained_begin() API allows scsi-disk to message the
virtio-scsi HBA.

scsi_device_drained_begin() uses a drain counter so that multiple SCSI
devices can have overlapping drained sections. The HBA only sees one
pair of .drained_begin/end() calls.

After this commit, virtio-scsi no longer depends on hw/virtio's
ioeventfd aio_set_event_notifier(is_external=true). This commit is a
step towards removing the aio_disable_external() API.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230516190238.8401-19-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
master
Stefan Hajnoczi 2023-05-16 15:02:36 -04:00 committed by Kevin Wolf
parent 1665d9326f
commit 766aa2de0f
6 changed files with 127 additions and 12 deletions
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40
hw/scsi/scsi-bus.c
View File

@ -1669,6 +1669,46 @@ void scsi_device_purge_requests(SCSIDevice *sdev, SCSISense sense)
scsi_device_set_ua(sdev, sense);
}
void scsi_device_drained_begin(SCSIDevice *sdev)
{
SCSIBus *bus = DO_UPCAST(SCSIBus, qbus, sdev->qdev.parent_bus);
if (!bus) {
return;
}
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
assert(bus->drain_count < INT_MAX);
/*
* Multiple BlockBackends can be on a SCSIBus and each may begin/end
* draining at any time. Keep a counter so HBAs only see begin/end once.
*/
if (bus->drain_count++ == 0) {
trace_scsi_bus_drained_begin(bus, sdev);
if (bus->info->drained_begin) {
bus->info->drained_begin(bus);
}
}
}
void scsi_device_drained_end(SCSIDevice *sdev)
{
SCSIBus *bus = DO_UPCAST(SCSIBus, qbus, sdev->qdev.parent_bus);
if (!bus) {
return;
}
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
assert(bus->drain_count > 0);
if (bus->drain_count-- == 1) {
trace_scsi_bus_drained_end(bus, sdev);
if (bus->info->drained_end) {
bus->info->drained_end(bus);
}
}
}
static char *scsibus_get_dev_path(DeviceState *dev)
{
SCSIDevice *d = SCSI_DEVICE(dev);

27
hw/scsi/scsi-disk.c
View File

@ -2360,6 +2360,20 @@ static void scsi_disk_reset(DeviceState *dev)
s->qdev.scsi_version = s->qdev.default_scsi_version;
}
static void scsi_disk_drained_begin(void *opaque)
{
SCSIDiskState *s = opaque;
scsi_device_drained_begin(&s->qdev);
}
static void scsi_disk_drained_end(void *opaque)
{
SCSIDiskState *s = opaque;
scsi_device_drained_end(&s->qdev);
}
static void scsi_disk_resize_cb(void *opaque)
{
SCSIDiskState *s = opaque;
@ -2414,16 +2428,19 @@ static bool scsi_cd_is_medium_locked(void *opaque)
}
static const BlockDevOps scsi_disk_removable_block_ops = {
.change_media_cb = scsi_cd_change_media_cb,
.change_media_cb = scsi_cd_change_media_cb,
.drained_begin = scsi_disk_drained_begin,
.drained_end = scsi_disk_drained_end,
.eject_request_cb = scsi_cd_eject_request_cb,
.is_tray_open = scsi_cd_is_tray_open,
.is_medium_locked = scsi_cd_is_medium_locked,
.resize_cb = scsi_disk_resize_cb,
.is_tray_open = scsi_cd_is_tray_open,
.resize_cb = scsi_disk_resize_cb,
};
static const BlockDevOps scsi_disk_block_ops = {
.resize_cb = scsi_disk_resize_cb,
.drained_begin = scsi_disk_drained_begin,
.drained_end = scsi_disk_drained_end,
.resize_cb = scsi_disk_resize_cb,
};
static void scsi_disk_unit_attention_reported(SCSIDevice *dev)

2
hw/scsi/trace-events
View File

@ -6,6 +6,8 @@ scsi_req_cancel(int target, int lun, int tag) "target %d lun %d tag %d"
scsi_req_data(int target, int lun, int tag, int len) "target %d lun %d tag %d len %d"
scsi_req_data_canceled(int target, int lun, int tag, int len) "target %d lun %d tag %d len %d"
scsi_req_dequeue(int target, int lun, int tag) "target %d lun %d tag %d"
scsi_bus_drained_begin(void *bus, void *sdev) "bus %p sdev %p"
scsi_bus_drained_end(void *bus, void *sdev) "bus %p sdev %p"
scsi_req_continue(int target, int lun, int tag) "target %d lun %d tag %d"
scsi_req_continue_canceled(int target, int lun, int tag) "target %d lun %d tag %d"
scsi_req_parsed(int target, int lun, int tag, int cmd, int mode, int xfer) "target %d lun %d tag %d command %d dir %d length %d"

18
hw/scsi/virtio-scsi-dataplane.c
View File

@ -158,14 +158,16 @@ int virtio_scsi_dataplane_start(VirtIODevice *vdev)
s->dataplane_starting = false;
s->dataplane_started = true;
aio_context_acquire(s->ctx);
virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx);
virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);
if (s->bus.drain_count == 0) {
aio_context_acquire(s->ctx);
virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx);
virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);
for (i = 0; i < vs->conf.num_queues; i++) {
virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx);
for (i = 0; i < vs->conf.num_queues; i++) {
virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx);
}
aio_context_release(s->ctx);
}
aio_context_release(s->ctx);
return 0;
fail_host_notifiers:
@ -211,7 +213,9 @@ void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
}
s->dataplane_stopping = true;
aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
if (s->bus.drain_count == 0) {
aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
}
blk_drain_all(); /* ensure there are no in-flight requests */

38
hw/scsi/virtio-scsi.c
View File

@ -1117,6 +1117,42 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev,
}
}
/* Suspend virtqueue ioeventfd processing during drain */
static void virtio_scsi_drained_begin(SCSIBus *bus)
{
VirtIOSCSI *s = container_of(bus, VirtIOSCSI, bus);
VirtIODevice *vdev = VIRTIO_DEVICE(s);
uint32_t total_queues = VIRTIO_SCSI_VQ_NUM_FIXED +
s->parent_obj.conf.num_queues;
if (!s->dataplane_started) {
return;
}
for (uint32_t i = 0; i < total_queues; i++) {
VirtQueue *vq = virtio_get_queue(vdev, i);
virtio_queue_aio_detach_host_notifier(vq, s->ctx);
}
}
/* Resume virtqueue ioeventfd processing after drain */
static void virtio_scsi_drained_end(SCSIBus *bus)
{
VirtIOSCSI *s = container_of(bus, VirtIOSCSI, bus);
VirtIODevice *vdev = VIRTIO_DEVICE(s);
uint32_t total_queues = VIRTIO_SCSI_VQ_NUM_FIXED +
s->parent_obj.conf.num_queues;
if (!s->dataplane_started) {
return;
}
for (uint32_t i = 0; i < total_queues; i++) {
VirtQueue *vq = virtio_get_queue(vdev, i);
virtio_queue_aio_attach_host_notifier(vq, s->ctx);
}
}
static struct SCSIBusInfo virtio_scsi_scsi_info = {
.tcq = true,
.max_channel = VIRTIO_SCSI_MAX_CHANNEL,
@ -1131,6 +1167,8 @@ static struct SCSIBusInfo virtio_scsi_scsi_info = {
.get_sg_list = virtio_scsi_get_sg_list,
.save_request = virtio_scsi_save_request,
.load_request = virtio_scsi_load_request,
.drained_begin = virtio_scsi_drained_begin,
.drained_end = virtio_scsi_drained_end,
};
void virtio_scsi_common_realize(DeviceState *dev,

14
include/hw/scsi/scsi.h
View File

@ -133,6 +133,16 @@ struct SCSIBusInfo {
void (*save_request)(QEMUFile *f, SCSIRequest *req);
void *(*load_request)(QEMUFile *f, SCSIRequest *req);
void (*free_request)(SCSIBus *bus, void *priv);
/*
* Temporarily stop submitting new requests between drained_begin() and
* drained_end(). Called from the main loop thread with the BQL held.
*
* Implement these callbacks if request processing is triggered by a file
* descriptor like an EventNotifier. Otherwise set them to NULL.
*/
void (*drained_begin)(SCSIBus *bus);
void (*drained_end)(SCSIBus *bus);
};
#define TYPE_SCSI_BUS "SCSI"
@ -144,6 +154,8 @@ struct SCSIBus {
SCSISense unit_attention;
const SCSIBusInfo *info;
int drain_count; /* protected by BQL */
};
/**
@ -213,6 +225,8 @@ void scsi_req_cancel_complete(SCSIRequest *req);
void scsi_req_cancel(SCSIRequest *req);
void scsi_req_cancel_async(SCSIRequest *req, Notifier *notifier);
void scsi_req_retry(SCSIRequest *req);
void scsi_device_drained_begin(SCSIDevice *sdev);
void scsi_device_drained_end(SCSIDevice *sdev);
void scsi_device_purge_requests(SCSIDevice *sdev, SCSISense sense);
void scsi_device_set_ua(SCSIDevice *sdev, SCSISense sense);
void scsi_device_report_change(SCSIDevice *dev, SCSISense sense);