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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v4 18/20] 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@xxxxxxxxxx>
---
include/hw/scsi/scsi.h | 14 ++++++++++++
hw/scsi/scsi-bus.c | 40 +++++++++++++++++++++++++++++++++
hw/scsi/scsi-disk.c | 27 +++++++++++++++++-----
hw/scsi/virtio-scsi-dataplane.c | 22 ++++++++++--------
hw/scsi/virtio-scsi.c | 38 +++++++++++++++++++++++++++++++
hw/scsi/trace-events | 2 ++
6 files changed, 129 insertions(+), 14 deletions(-)
diff --git a/include/hw/scsi/scsi.h b/include/hw/scsi/scsi.h
index 6f23a7a73e..e2bb1a2fbf 100644
--- a/include/hw/scsi/scsi.h
+++ b/include/hw/scsi/scsi.h
@@ -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);
diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
index 64d7311757..b571fdf895 100644
--- a/hw/scsi/scsi-bus.c
+++ b/hw/scsi/scsi-bus.c
@@ -1668,6 +1668,46 @@ 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);
diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index e01bd84541..2249087d6a 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -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)
diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index 81643445ed..1060038e13 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -153,14 +153,16 @@ 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:
@@ -206,9 +208,11 @@ void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
}
s->dataplane_stopping = true;
- aio_context_acquire(s->ctx);
- aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
- aio_context_release(s->ctx);
+ if (s->bus.drain_count == 0) {
+ aio_context_acquire(s->ctx);
+ aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
+ aio_context_release(s->ctx);
+ }
blk_drain_all(); /* ensure there are no in-flight requests */
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index a02f9233ec..eba1e84dac 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -1081,6 +1081,42 @@ 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,
@@ -1095,6 +1131,8 @@ 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,
diff --git a/hw/scsi/trace-events b/hw/scsi/trace-events
index ab238293f0..bdd4e2c7c7 100644
--- a/hw/scsi/trace-events
+++ b/hw/scsi/trace-events
@@ -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"
--
2.39.2
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