[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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