Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 1157 insertions, 0 deletions

diff --git a/kernel/drivers/scsi/virtio_scsi.c b/kernel/drivers/scsi/virtio_scsi.c
new file mode 100644
index 000000000..f164f24a4
--- /dev/null
+++ b/kernel/drivers/scsi/virtio_scsi.c
@@ -0,0 +1,1157 @@
+/*
+ * Virtio SCSI HBA driver
+ *
+ * Copyright IBM Corp. 2010
+ * Copyright Red Hat, Inc. 2011
+ *
+ * Authors:
+ *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
+ *  Paolo Bonzini   <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mempool.h>
+#include <linux/virtio.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_scsi.h>
+#include <linux/cpu.h>
+#include <linux/blkdev.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_tcq.h>
+#include <linux/seqlock.h>
+
+#define VIRTIO_SCSI_MEMPOOL_SZ 64
+#define VIRTIO_SCSI_EVENT_LEN 8
+#define VIRTIO_SCSI_VQ_BASE 2
+
+/* Command queue element */
+struct virtio_scsi_cmd {
+	struct scsi_cmnd *sc;
+	struct completion *comp;
+	union {
+		struct virtio_scsi_cmd_req       cmd;
+		struct virtio_scsi_cmd_req_pi    cmd_pi;
+		struct virtio_scsi_ctrl_tmf_req  tmf;
+		struct virtio_scsi_ctrl_an_req   an;
+	} req;
+	union {
+		struct virtio_scsi_cmd_resp      cmd;
+		struct virtio_scsi_ctrl_tmf_resp tmf;
+		struct virtio_scsi_ctrl_an_resp  an;
+		struct virtio_scsi_event         evt;
+	} resp;
+} ____cacheline_aligned_in_smp;
+
+struct virtio_scsi_event_node {
+	struct virtio_scsi *vscsi;
+	struct virtio_scsi_event event;
+	struct work_struct work;
+};
+
+struct virtio_scsi_vq {
+	/* Protects vq */
+	spinlock_t vq_lock;
+
+	struct virtqueue *vq;
+};
+
+/*
+ * Per-target queue state.
+ *
+ * This struct holds the data needed by the queue steering policy.  When a
+ * target is sent multiple requests, we need to drive them to the same queue so
+ * that FIFO processing order is kept.  However, if a target was idle, we can
+ * choose a queue arbitrarily.  In this case the queue is chosen according to
+ * the current VCPU, so the driver expects the number of request queues to be
+ * equal to the number of VCPUs.  This makes it easy and fast to select the
+ * queue, and also lets the driver optimize the IRQ affinity for the virtqueues
+ * (each virtqueue's affinity is set to the CPU that "owns" the queue).
+ *
+ * tgt_seq is held to serialize reading and writing req_vq.
+ *
+ * Decrements of reqs are never concurrent with writes of req_vq: before the
+ * decrement reqs will be != 0; after the decrement the virtqueue completion
+ * routine will not use the req_vq so it can be changed by a new request.
+ * Thus they can happen outside the tgt_seq, provided of course we make reqs
+ * an atomic_t.
+ */
+struct virtio_scsi_target_state {
+	seqcount_t tgt_seq;
+
+	/* Count of outstanding requests. */
+	atomic_t reqs;
+
+	/* Currently active virtqueue for requests sent to this target. */
+	struct virtio_scsi_vq *req_vq;
+};
+
+/* Driver instance state */
+struct virtio_scsi {
+	struct virtio_device *vdev;
+
+	/* Get some buffers ready for event vq */
+	struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
+
+	u32 num_queues;
+
+	/* If the affinity hint is set for virtqueues */
+	bool affinity_hint_set;
+
+	/* CPU hotplug notifier */
+	struct notifier_block nb;
+
+	/* Protected by event_vq lock */
+	bool stop_events;
+
+	struct virtio_scsi_vq ctrl_vq;
+	struct virtio_scsi_vq event_vq;
+	struct virtio_scsi_vq req_vqs[];
+};
+
+static struct kmem_cache *virtscsi_cmd_cache;
+static mempool_t *virtscsi_cmd_pool;
+
+static inline struct Scsi_Host *virtio_scsi_host(struct virtio_device *vdev)
+{
+	return vdev->priv;
+}
+
+static void virtscsi_compute_resid(struct scsi_cmnd *sc, u32 resid)
+{
+	if (!resid)
+		return;
+
+	if (!scsi_bidi_cmnd(sc)) {
+		scsi_set_resid(sc, resid);
+		return;
+	}
+
+	scsi_in(sc)->resid = min(resid, scsi_in(sc)->length);
+	scsi_out(sc)->resid = resid - scsi_in(sc)->resid;
+}
+
+/**
+ * virtscsi_complete_cmd - finish a scsi_cmd and invoke scsi_done
+ *
+ * Called with vq_lock held.
+ */
+static void virtscsi_complete_cmd(struct virtio_scsi *vscsi, void *buf)
+{
+	struct virtio_scsi_cmd *cmd = buf;
+	struct scsi_cmnd *sc = cmd->sc;
+	struct virtio_scsi_cmd_resp *resp = &cmd->resp.cmd;
+	struct virtio_scsi_target_state *tgt =
+				scsi_target(sc->device)->hostdata;
+
+	dev_dbg(&sc->device->sdev_gendev,
+		"cmd %p response %u status %#02x sense_len %u\n",
+		sc, resp->response, resp->status, resp->sense_len);
+
+	sc->result = resp->status;
+	virtscsi_compute_resid(sc, virtio32_to_cpu(vscsi->vdev, resp->resid));
+	switch (resp->response) {
+	case VIRTIO_SCSI_S_OK:
+		set_host_byte(sc, DID_OK);
+		break;
+	case VIRTIO_SCSI_S_OVERRUN:
+		set_host_byte(sc, DID_ERROR);
+		break;
+	case VIRTIO_SCSI_S_ABORTED:
+		set_host_byte(sc, DID_ABORT);
+		break;
+	case VIRTIO_SCSI_S_BAD_TARGET:
+		set_host_byte(sc, DID_BAD_TARGET);
+		break;
+	case VIRTIO_SCSI_S_RESET:
+		set_host_byte(sc, DID_RESET);
+		break;
+	case VIRTIO_SCSI_S_BUSY:
+		set_host_byte(sc, DID_BUS_BUSY);
+		break;
+	case VIRTIO_SCSI_S_TRANSPORT_FAILURE:
+		set_host_byte(sc, DID_TRANSPORT_DISRUPTED);
+		break;
+	case VIRTIO_SCSI_S_TARGET_FAILURE:
+		set_host_byte(sc, DID_TARGET_FAILURE);
+		break;
+	case VIRTIO_SCSI_S_NEXUS_FAILURE:
+		set_host_byte(sc, DID_NEXUS_FAILURE);
+		break;
+	default:
+		scmd_printk(KERN_WARNING, sc, "Unknown response %d",
+			    resp->response);
+		/* fall through */
+	case VIRTIO_SCSI_S_FAILURE:
+		set_host_byte(sc, DID_ERROR);
+		break;
+	}
+
+	WARN_ON(virtio32_to_cpu(vscsi->vdev, resp->sense_len) >
+		VIRTIO_SCSI_SENSE_SIZE);
+	if (sc->sense_buffer) {
+		memcpy(sc->sense_buffer, resp->sense,
+		       min_t(u32,
+			     virtio32_to_cpu(vscsi->vdev, resp->sense_len),
+			     VIRTIO_SCSI_SENSE_SIZE));
+		if (resp->sense_len)
+			set_driver_byte(sc, DRIVER_SENSE);
+	}
+
+	sc->scsi_done(sc);
+
+	atomic_dec(&tgt->reqs);
+}
+
+static void virtscsi_vq_done(struct virtio_scsi *vscsi,
+			     struct virtio_scsi_vq *virtscsi_vq,
+			     void (*fn)(struct virtio_scsi *vscsi, void *buf))
+{
+	void *buf;
+	unsigned int len;
+	unsigned long flags;
+	struct virtqueue *vq = virtscsi_vq->vq;
+
+	spin_lock_irqsave(&virtscsi_vq->vq_lock, flags);
+	do {
+		virtqueue_disable_cb(vq);
+		while ((buf = virtqueue_get_buf(vq, &len)) != NULL)
+			fn(vscsi, buf);
+
+		if (unlikely(virtqueue_is_broken(vq)))
+			break;
+	} while (!virtqueue_enable_cb(vq));
+	spin_unlock_irqrestore(&virtscsi_vq->vq_lock, flags);
+}
+
+static void virtscsi_req_done(struct virtqueue *vq)
+{
+	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+	int index = vq->index - VIRTIO_SCSI_VQ_BASE;
+	struct virtio_scsi_vq *req_vq = &vscsi->req_vqs[index];
+
+	virtscsi_vq_done(vscsi, req_vq, virtscsi_complete_cmd);
+};
+
+static void virtscsi_poll_requests(struct virtio_scsi *vscsi)
+{
+	int i, num_vqs;
+
+	num_vqs = vscsi->num_queues;
+	for (i = 0; i < num_vqs; i++)
+		virtscsi_vq_done(vscsi, &vscsi->req_vqs[i],
+				 virtscsi_complete_cmd);
+}
+
+static void virtscsi_complete_free(struct virtio_scsi *vscsi, void *buf)
+{
+	struct virtio_scsi_cmd *cmd = buf;
+
+	if (cmd->comp)
+		complete_all(cmd->comp);
+}
+
+static void virtscsi_ctrl_done(struct virtqueue *vq)
+{
+	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+
+	virtscsi_vq_done(vscsi, &vscsi->ctrl_vq, virtscsi_complete_free);
+};
+
+static void virtscsi_handle_event(struct work_struct *work);
+
+static int virtscsi_kick_event(struct virtio_scsi *vscsi,
+			       struct virtio_scsi_event_node *event_node)
+{
+	int err;
+	struct scatterlist sg;
+	unsigned long flags;
+
+	INIT_WORK(&event_node->work, virtscsi_handle_event);
+	sg_init_one(&sg, &event_node->event, sizeof(struct virtio_scsi_event));
+
+	spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
+
+	err = virtqueue_add_inbuf(vscsi->event_vq.vq, &sg, 1, event_node,
+				  GFP_ATOMIC);
+	if (!err)
+		virtqueue_kick(vscsi->event_vq.vq);
+
+	spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
+
+	return err;
+}
+
+static int virtscsi_kick_event_all(struct virtio_scsi *vscsi)
+{
+	int i;
+
+	for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++) {
+		vscsi->event_list[i].vscsi = vscsi;
+		virtscsi_kick_event(vscsi, &vscsi->event_list[i]);
+	}
+
+	return 0;
+}
+
+static void virtscsi_cancel_event_work(struct virtio_scsi *vscsi)
+{
+	int i;
+
+	/* Stop scheduling work before calling cancel_work_sync.  */
+	spin_lock_irq(&vscsi->event_vq.vq_lock);
+	vscsi->stop_events = true;
+	spin_unlock_irq(&vscsi->event_vq.vq_lock);
+
+	for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++)
+		cancel_work_sync(&vscsi->event_list[i].work);
+}
+
+static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
+					    struct virtio_scsi_event *event)
+{
+	struct scsi_device *sdev;
+	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
+	unsigned int target = event->lun[1];
+	unsigned int lun = (event->lun[2] << 8) | event->lun[3];
+
+	switch (virtio32_to_cpu(vscsi->vdev, event->reason)) {
+	case VIRTIO_SCSI_EVT_RESET_RESCAN:
+		scsi_add_device(shost, 0, target, lun);
+		break;
+	case VIRTIO_SCSI_EVT_RESET_REMOVED:
+		sdev = scsi_device_lookup(shost, 0, target, lun);
+		if (sdev) {
+			scsi_remove_device(sdev);
+			scsi_device_put(sdev);
+		} else {
+			pr_err("SCSI device %d 0 %d %d not found\n",
+				shost->host_no, target, lun);
+		}
+		break;
+	default:
+		pr_info("Unsupport virtio scsi event reason %x\n", event->reason);
+	}
+}
+
+static void virtscsi_handle_param_change(struct virtio_scsi *vscsi,
+					 struct virtio_scsi_event *event)
+{
+	struct scsi_device *sdev;
+	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
+	unsigned int target = event->lun[1];
+	unsigned int lun = (event->lun[2] << 8) | event->lun[3];
+	u8 asc = virtio32_to_cpu(vscsi->vdev, event->reason) & 255;
+	u8 ascq = virtio32_to_cpu(vscsi->vdev, event->reason) >> 8;
+
+	sdev = scsi_device_lookup(shost, 0, target, lun);
+	if (!sdev) {
+		pr_err("SCSI device %d 0 %d %d not found\n",
+			shost->host_no, target, lun);
+		return;
+	}
+
+	/* Handle "Parameters changed", "Mode parameters changed", and
+	   "Capacity data has changed".  */
+	if (asc == 0x2a && (ascq == 0x00 || ascq == 0x01 || ascq == 0x09))
+		scsi_rescan_device(&sdev->sdev_gendev);
+
+	scsi_device_put(sdev);
+}
+
+static void virtscsi_handle_event(struct work_struct *work)
+{
+	struct virtio_scsi_event_node *event_node =
+		container_of(work, struct virtio_scsi_event_node, work);
+	struct virtio_scsi *vscsi = event_node->vscsi;
+	struct virtio_scsi_event *event = &event_node->event;
+
+	if (event->event &
+	    cpu_to_virtio32(vscsi->vdev, VIRTIO_SCSI_T_EVENTS_MISSED)) {
+		event->event &= ~cpu_to_virtio32(vscsi->vdev,
+						   VIRTIO_SCSI_T_EVENTS_MISSED);
+		scsi_scan_host(virtio_scsi_host(vscsi->vdev));
+	}
+
+	switch (virtio32_to_cpu(vscsi->vdev, event->event)) {
+	case VIRTIO_SCSI_T_NO_EVENT:
+		break;
+	case VIRTIO_SCSI_T_TRANSPORT_RESET:
+		virtscsi_handle_transport_reset(vscsi, event);
+		break;
+	case VIRTIO_SCSI_T_PARAM_CHANGE:
+		virtscsi_handle_param_change(vscsi, event);
+		break;
+	default:
+		pr_err("Unsupport virtio scsi event %x\n", event->event);
+	}
+	virtscsi_kick_event(vscsi, event_node);
+}
+
+static void virtscsi_complete_event(struct virtio_scsi *vscsi, void *buf)
+{
+	struct virtio_scsi_event_node *event_node = buf;
+
+	if (!vscsi->stop_events)
+		queue_work(system_freezable_wq, &event_node->work);
+}
+
+static void virtscsi_event_done(struct virtqueue *vq)
+{
+	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+
+	virtscsi_vq_done(vscsi, &vscsi->event_vq, virtscsi_complete_event);
+};
+
+/**
+ * virtscsi_add_cmd - add a virtio_scsi_cmd to a virtqueue
+ * @vq		: the struct virtqueue we're talking about
+ * @cmd		: command structure
+ * @req_size	: size of the request buffer
+ * @resp_size	: size of the response buffer
+ */
+static int virtscsi_add_cmd(struct virtqueue *vq,
+			    struct virtio_scsi_cmd *cmd,
+			    size_t req_size, size_t resp_size)
+{
+	struct scsi_cmnd *sc = cmd->sc;
+	struct scatterlist *sgs[6], req, resp;
+	struct sg_table *out, *in;
+	unsigned out_num = 0, in_num = 0;
+
+	out = in = NULL;
+
+	if (sc && sc->sc_data_direction != DMA_NONE) {
+		if (sc->sc_data_direction != DMA_FROM_DEVICE)
+			out = &scsi_out(sc)->table;
+		if (sc->sc_data_direction != DMA_TO_DEVICE)
+			in = &scsi_in(sc)->table;
+	}
+
+	/* Request header.  */
+	sg_init_one(&req, &cmd->req, req_size);
+	sgs[out_num++] = &req;
+
+	/* Data-out buffer.  */
+	if (out) {
+		/* Place WRITE protection SGLs before Data OUT payload */
+		if (scsi_prot_sg_count(sc))
+			sgs[out_num++] = scsi_prot_sglist(sc);
+		sgs[out_num++] = out->sgl;
+	}
+
+	/* Response header.  */
+	sg_init_one(&resp, &cmd->resp, resp_size);
+	sgs[out_num + in_num++] = &resp;
+
+	/* Data-in buffer */
+	if (in) {
+		/* Place READ protection SGLs before Data IN payload */
+		if (scsi_prot_sg_count(sc))
+			sgs[out_num + in_num++] = scsi_prot_sglist(sc);
+		sgs[out_num + in_num++] = in->sgl;
+	}
+
+	return virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_ATOMIC);
+}
+
+static int virtscsi_kick_cmd(struct virtio_scsi_vq *vq,
+			     struct virtio_scsi_cmd *cmd,
+			     size_t req_size, size_t resp_size)
+{
+	unsigned long flags;
+	int err;
+	bool needs_kick = false;
+
+	spin_lock_irqsave(&vq->vq_lock, flags);
+	err = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size);
+	if (!err)
+		needs_kick = virtqueue_kick_prepare(vq->vq);
+
+	spin_unlock_irqrestore(&vq->vq_lock, flags);
+
+	if (needs_kick)
+		virtqueue_notify(vq->vq);
+	return err;
+}
+
+static void virtio_scsi_init_hdr(struct virtio_device *vdev,
+				 struct virtio_scsi_cmd_req *cmd,
+				 struct scsi_cmnd *sc)
+{
+	cmd->lun[0] = 1;
+	cmd->lun[1] = sc->device->id;
+	cmd->lun[2] = (sc->device->lun >> 8) | 0x40;
+	cmd->lun[3] = sc->device->lun & 0xff;
+	cmd->tag = cpu_to_virtio64(vdev, (unsigned long)sc);
+	cmd->task_attr = VIRTIO_SCSI_S_SIMPLE;
+	cmd->prio = 0;
+	cmd->crn = 0;
+}
+
+static void virtio_scsi_init_hdr_pi(struct virtio_device *vdev,
+				    struct virtio_scsi_cmd_req_pi *cmd_pi,
+				    struct scsi_cmnd *sc)
+{
+	struct request *rq = sc->request;
+	struct blk_integrity *bi;
+
+	virtio_scsi_init_hdr(vdev, (struct virtio_scsi_cmd_req *)cmd_pi, sc);
+
+	if (!rq || !scsi_prot_sg_count(sc))
+		return;
+
+	bi = blk_get_integrity(rq->rq_disk);
+
+	if (sc->sc_data_direction == DMA_TO_DEVICE)
+		cmd_pi->pi_bytesout = cpu_to_virtio32(vdev,
+							blk_rq_sectors(rq) *
+							bi->tuple_size);
+	else if (sc->sc_data_direction == DMA_FROM_DEVICE)
+		cmd_pi->pi_bytesin = cpu_to_virtio32(vdev,
+						       blk_rq_sectors(rq) *
+						       bi->tuple_size);
+}
+
+static int virtscsi_queuecommand(struct virtio_scsi *vscsi,
+				 struct virtio_scsi_vq *req_vq,
+				 struct scsi_cmnd *sc)
+{
+	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
+	struct virtio_scsi_cmd *cmd = scsi_cmd_priv(sc);
+	int req_size;
+
+	BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize);
+
+	/* TODO: check feature bit and fail if unsupported?  */
+	BUG_ON(sc->sc_data_direction == DMA_BIDIRECTIONAL);
+
+	dev_dbg(&sc->device->sdev_gendev,
+		"cmd %p CDB: %#02x\n", sc, sc->cmnd[0]);
+
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->sc = sc;
+
+	BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);
+
+	if (virtio_has_feature(vscsi->vdev, VIRTIO_SCSI_F_T10_PI)) {
+		virtio_scsi_init_hdr_pi(vscsi->vdev, &cmd->req.cmd_pi, sc);
+		memcpy(cmd->req.cmd_pi.cdb, sc->cmnd, sc->cmd_len);
+		req_size = sizeof(cmd->req.cmd_pi);
+	} else {
+		virtio_scsi_init_hdr(vscsi->vdev, &cmd->req.cmd, sc);
+		memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);
+		req_size = sizeof(cmd->req.cmd);
+	}
+
+	if (virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)) != 0)
+		return SCSI_MLQUEUE_HOST_BUSY;
+	return 0;
+}
+
+static int virtscsi_queuecommand_single(struct Scsi_Host *sh,
+					struct scsi_cmnd *sc)
+{
+	struct virtio_scsi *vscsi = shost_priv(sh);
+	struct virtio_scsi_target_state *tgt =
+				scsi_target(sc->device)->hostdata;
+
+	atomic_inc(&tgt->reqs);
+	return virtscsi_queuecommand(vscsi, &vscsi->req_vqs[0], sc);
+}
+
+static struct virtio_scsi_vq *virtscsi_pick_vq_mq(struct virtio_scsi *vscsi,
+						  struct scsi_cmnd *sc)
+{
+	u32 tag = blk_mq_unique_tag(sc->request);
+	u16 hwq = blk_mq_unique_tag_to_hwq(tag);
+
+	return &vscsi->req_vqs[hwq];
+}
+
+static struct virtio_scsi_vq *virtscsi_pick_vq(struct virtio_scsi *vscsi,
+					       struct virtio_scsi_target_state *tgt)
+{
+	struct virtio_scsi_vq *vq;
+	unsigned long flags;
+	u32 queue_num;
+
+	local_irq_save(flags);
+	if (atomic_inc_return(&tgt->reqs) > 1) {
+		unsigned long seq;
+
+		do {
+			seq = read_seqcount_begin(&tgt->tgt_seq);
+			vq = tgt->req_vq;
+		} while (read_seqcount_retry(&tgt->tgt_seq, seq));
+	} else {
+		/* no writes can be concurrent because of atomic_t */
+		write_seqcount_begin(&tgt->tgt_seq);
+
+		/* keep previous req_vq if a reader just arrived */
+		if (unlikely(atomic_read(&tgt->reqs) > 1)) {
+			vq = tgt->req_vq;
+			goto unlock;
+		}
+
+		queue_num = smp_processor_id();
+		while (unlikely(queue_num >= vscsi->num_queues))
+			queue_num -= vscsi->num_queues;
+		tgt->req_vq = vq = &vscsi->req_vqs[queue_num];
+ unlock:
+		write_seqcount_end(&tgt->tgt_seq);
+	}
+	local_irq_restore(flags);
+
+	return vq;
+}
+
+static int virtscsi_queuecommand_multi(struct Scsi_Host *sh,
+				       struct scsi_cmnd *sc)
+{
+	struct virtio_scsi *vscsi = shost_priv(sh);
+	struct virtio_scsi_target_state *tgt =
+				scsi_target(sc->device)->hostdata;
+	struct virtio_scsi_vq *req_vq;
+
+	if (shost_use_blk_mq(sh))
+		req_vq = virtscsi_pick_vq_mq(vscsi, sc);
+	else
+		req_vq = virtscsi_pick_vq(vscsi, tgt);
+
+	return virtscsi_queuecommand(vscsi, req_vq, sc);
+}
+
+static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
+{
+	DECLARE_COMPLETION_ONSTACK(comp);
+	int ret = FAILED;
+
+	cmd->comp = &comp;
+	if (virtscsi_kick_cmd(&vscsi->ctrl_vq, cmd,
+			      sizeof cmd->req.tmf, sizeof cmd->resp.tmf) < 0)
+		goto out;
+
+	wait_for_completion(&comp);
+	if (cmd->resp.tmf.response == VIRTIO_SCSI_S_OK ||
+	    cmd->resp.tmf.response == VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
+		ret = SUCCESS;
+
+	/*
+	 * The spec guarantees that all requests related to the TMF have
+	 * been completed, but the callback might not have run yet if
+	 * we're using independent interrupts (e.g. MSI).  Poll the
+	 * virtqueues once.
+	 *
+	 * In the abort case, sc->scsi_done will do nothing, because
+	 * the block layer must have detected a timeout and as a result
+	 * REQ_ATOM_COMPLETE has been set.
+	 */
+	virtscsi_poll_requests(vscsi);
+
+out:
+	mempool_free(cmd, virtscsi_cmd_pool);
+	return ret;
+}
+
+static int virtscsi_device_reset(struct scsi_cmnd *sc)
+{
+	struct virtio_scsi *vscsi = shost_priv(sc->device->host);
+	struct virtio_scsi_cmd *cmd;
+
+	sdev_printk(KERN_INFO, sc->device, "device reset\n");
+	cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
+	if (!cmd)
+		return FAILED;
+
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->sc = sc;
+	cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
+		.type = VIRTIO_SCSI_T_TMF,
+		.subtype = cpu_to_virtio32(vscsi->vdev,
+					     VIRTIO_SCSI_T_TMF_LOGICAL_UNIT_RESET),
+		.lun[0] = 1,
+		.lun[1] = sc->device->id,
+		.lun[2] = (sc->device->lun >> 8) | 0x40,
+		.lun[3] = sc->device->lun & 0xff,
+	};
+	return virtscsi_tmf(vscsi, cmd);
+}
+
+/**
+ * virtscsi_change_queue_depth() - Change a virtscsi target's queue depth
+ * @sdev:	Virtscsi target whose queue depth to change
+ * @qdepth:	New queue depth
+ */
+static int virtscsi_change_queue_depth(struct scsi_device *sdev, int qdepth)
+{
+	struct Scsi_Host *shost = sdev->host;
+	int max_depth = shost->cmd_per_lun;
+
+	return scsi_change_queue_depth(sdev, min(max_depth, qdepth));
+}
+
+static int virtscsi_abort(struct scsi_cmnd *sc)
+{
+	struct virtio_scsi *vscsi = shost_priv(sc->device->host);
+	struct virtio_scsi_cmd *cmd;
+
+	scmd_printk(KERN_INFO, sc, "abort\n");
+	cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
+	if (!cmd)
+		return FAILED;
+
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->sc = sc;
+	cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
+		.type = VIRTIO_SCSI_T_TMF,
+		.subtype = VIRTIO_SCSI_T_TMF_ABORT_TASK,
+		.lun[0] = 1,
+		.lun[1] = sc->device->id,
+		.lun[2] = (sc->device->lun >> 8) | 0x40,
+		.lun[3] = sc->device->lun & 0xff,
+		.tag = cpu_to_virtio64(vscsi->vdev, (unsigned long)sc),
+	};
+	return virtscsi_tmf(vscsi, cmd);
+}
+
+static int virtscsi_target_alloc(struct scsi_target *starget)
+{
+	struct Scsi_Host *sh = dev_to_shost(starget->dev.parent);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+
+	struct virtio_scsi_target_state *tgt =
+				kmalloc(sizeof(*tgt), GFP_KERNEL);
+	if (!tgt)
+		return -ENOMEM;
+
+	seqcount_init(&tgt->tgt_seq);
+	atomic_set(&tgt->reqs, 0);
+	tgt->req_vq = &vscsi->req_vqs[0];
+
+	starget->hostdata = tgt;
+	return 0;
+}
+
+static void virtscsi_target_destroy(struct scsi_target *starget)
+{
+	struct virtio_scsi_target_state *tgt = starget->hostdata;
+	kfree(tgt);
+}
+
+static struct scsi_host_template virtscsi_host_template_single = {
+	.module = THIS_MODULE,
+	.name = "Virtio SCSI HBA",
+	.proc_name = "virtio_scsi",
+	.this_id = -1,
+	.cmd_size = sizeof(struct virtio_scsi_cmd),
+	.queuecommand = virtscsi_queuecommand_single,
+	.change_queue_depth = virtscsi_change_queue_depth,
+	.eh_abort_handler = virtscsi_abort,
+	.eh_device_reset_handler = virtscsi_device_reset,
+
+	.can_queue = 1024,
+	.dma_boundary = UINT_MAX,
+	.use_clustering = ENABLE_CLUSTERING,
+	.target_alloc = virtscsi_target_alloc,
+	.target_destroy = virtscsi_target_destroy,
+	.track_queue_depth = 1,
+};
+
+static struct scsi_host_template virtscsi_host_template_multi = {
+	.module = THIS_MODULE,
+	.name = "Virtio SCSI HBA",
+	.proc_name = "virtio_scsi",
+	.this_id = -1,
+	.cmd_size = sizeof(struct virtio_scsi_cmd),
+	.queuecommand = virtscsi_queuecommand_multi,
+	.change_queue_depth = virtscsi_change_queue_depth,
+	.eh_abort_handler = virtscsi_abort,
+	.eh_device_reset_handler = virtscsi_device_reset,
+
+	.can_queue = 1024,
+	.dma_boundary = UINT_MAX,
+	.use_clustering = ENABLE_CLUSTERING,
+	.target_alloc = virtscsi_target_alloc,
+	.target_destroy = virtscsi_target_destroy,
+	.track_queue_depth = 1,
+};
+
+#define virtscsi_config_get(vdev, fld) \
+	({ \
+		typeof(((struct virtio_scsi_config *)0)->fld) __val; \
+		virtio_cread(vdev, struct virtio_scsi_config, fld, &__val); \
+		__val; \
+	})
+
+#define virtscsi_config_set(vdev, fld, val) \
+	do { \
+		typeof(((struct virtio_scsi_config *)0)->fld) __val = (val); \
+		virtio_cwrite(vdev, struct virtio_scsi_config, fld, &__val); \
+	} while(0)
+
+static void __virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
+{
+	int i;
+	int cpu;
+
+	/* In multiqueue mode, when the number of cpu is equal
+	 * to the number of request queues, we let the qeueues
+	 * to be private to one cpu by setting the affinity hint
+	 * to eliminate the contention.
+	 */
+	if ((vscsi->num_queues == 1 ||
+	     vscsi->num_queues != num_online_cpus()) && affinity) {
+		if (vscsi->affinity_hint_set)
+			affinity = false;
+		else
+			return;
+	}
+
+	if (affinity) {
+		i = 0;
+		for_each_online_cpu(cpu) {
+			virtqueue_set_affinity(vscsi->req_vqs[i].vq, cpu);
+			i++;
+		}
+
+		vscsi->affinity_hint_set = true;
+	} else {
+		for (i = 0; i < vscsi->num_queues; i++) {
+			if (!vscsi->req_vqs[i].vq)
+				continue;
+
+			virtqueue_set_affinity(vscsi->req_vqs[i].vq, -1);
+		}
+
+		vscsi->affinity_hint_set = false;
+	}
+}
+
+static void virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
+{
+	get_online_cpus();
+	__virtscsi_set_affinity(vscsi, affinity);
+	put_online_cpus();
+}
+
+static int virtscsi_cpu_callback(struct notifier_block *nfb,
+				 unsigned long action, void *hcpu)
+{
+	struct virtio_scsi *vscsi = container_of(nfb, struct virtio_scsi, nb);
+	switch(action) {
+	case CPU_ONLINE:
+	case CPU_ONLINE_FROZEN:
+	case CPU_DEAD:
+	case CPU_DEAD_FROZEN:
+		__virtscsi_set_affinity(vscsi, true);
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
+			     struct virtqueue *vq)
+{
+	spin_lock_init(&virtscsi_vq->vq_lock);
+	virtscsi_vq->vq = vq;
+}
+
+static void virtscsi_remove_vqs(struct virtio_device *vdev)
+{
+	struct Scsi_Host *sh = virtio_scsi_host(vdev);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+
+	virtscsi_set_affinity(vscsi, false);
+
+	/* Stop all the virtqueues. */
+	vdev->config->reset(vdev);
+
+	vdev->config->del_vqs(vdev);
+}
+
+static int virtscsi_init(struct virtio_device *vdev,
+			 struct virtio_scsi *vscsi)
+{
+	int err;
+	u32 i;
+	u32 num_vqs;
+	vq_callback_t **callbacks;
+	const char **names;
+	struct virtqueue **vqs;
+
+	num_vqs = vscsi->num_queues + VIRTIO_SCSI_VQ_BASE;
+	vqs = kmalloc(num_vqs * sizeof(struct virtqueue *), GFP_KERNEL);
+	callbacks = kmalloc(num_vqs * sizeof(vq_callback_t *), GFP_KERNEL);
+	names = kmalloc(num_vqs * sizeof(char *), GFP_KERNEL);
+
+	if (!callbacks || !vqs || !names) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	callbacks[0] = virtscsi_ctrl_done;
+	callbacks[1] = virtscsi_event_done;
+	names[0] = "control";
+	names[1] = "event";
+	for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++) {
+		callbacks[i] = virtscsi_req_done;
+		names[i] = "request";
+	}
+
+	/* Discover virtqueues and write information to configuration.  */
+	err = vdev->config->find_vqs(vdev, num_vqs, vqs, callbacks, names);
+	if (err)
+		goto out;
+
+	virtscsi_init_vq(&vscsi->ctrl_vq, vqs[0]);
+	virtscsi_init_vq(&vscsi->event_vq, vqs[1]);
+	for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++)
+		virtscsi_init_vq(&vscsi->req_vqs[i - VIRTIO_SCSI_VQ_BASE],
+				 vqs[i]);
+
+	virtscsi_set_affinity(vscsi, true);
+
+	virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
+	virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);
+
+	err = 0;
+
+out:
+	kfree(names);
+	kfree(callbacks);
+	kfree(vqs);
+	if (err)
+		virtscsi_remove_vqs(vdev);
+	return err;
+}
+
+static int virtscsi_probe(struct virtio_device *vdev)
+{
+	struct Scsi_Host *shost;
+	struct virtio_scsi *vscsi;
+	int err, host_prot;
+	u32 sg_elems, num_targets;
+	u32 cmd_per_lun;
+	u32 num_queues;
+	struct scsi_host_template *hostt;
+
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config access disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	/* We need to know how many queues before we allocate. */
+	num_queues = virtscsi_config_get(vdev, num_queues) ? : 1;
+
+	num_targets = virtscsi_config_get(vdev, max_target) + 1;
+
+	if (num_queues == 1)
+		hostt = &virtscsi_host_template_single;
+	else
+		hostt = &virtscsi_host_template_multi;
+
+	shost = scsi_host_alloc(hostt,
+		sizeof(*vscsi) + sizeof(vscsi->req_vqs[0]) * num_queues);
+	if (!shost)
+		return -ENOMEM;
+
+	sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
+	shost->sg_tablesize = sg_elems;
+	vscsi = shost_priv(shost);
+	vscsi->vdev = vdev;
+	vscsi->num_queues = num_queues;
+	vdev->priv = shost;
+
+	err = virtscsi_init(vdev, vscsi);
+	if (err)
+		goto virtscsi_init_failed;
+
+	vscsi->nb.notifier_call = &virtscsi_cpu_callback;
+	err = register_hotcpu_notifier(&vscsi->nb);
+	if (err) {
+		pr_err("registering cpu notifier failed\n");
+		goto scsi_add_host_failed;
+	}
+
+	cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
+	shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue);
+	shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF;
+
+	/* LUNs > 256 are reported with format 1, so they go in the range
+	 * 16640-32767.
+	 */
+	shost->max_lun = virtscsi_config_get(vdev, max_lun) + 1 + 0x4000;
+	shost->max_id = num_targets;
+	shost->max_channel = 0;
+	shost->max_cmd_len = VIRTIO_SCSI_CDB_SIZE;
+	shost->nr_hw_queues = num_queues;
+
+	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_T10_PI)) {
+		host_prot = SHOST_DIF_TYPE1_PROTECTION | SHOST_DIF_TYPE2_PROTECTION |
+			    SHOST_DIF_TYPE3_PROTECTION | SHOST_DIX_TYPE1_PROTECTION |
+			    SHOST_DIX_TYPE2_PROTECTION | SHOST_DIX_TYPE3_PROTECTION;
+
+		scsi_host_set_prot(shost, host_prot);
+		scsi_host_set_guard(shost, SHOST_DIX_GUARD_CRC);
+	}
+
+	err = scsi_add_host(shost, &vdev->dev);
+	if (err)
+		goto scsi_add_host_failed;
+
+	virtio_device_ready(vdev);
+
+	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
+		virtscsi_kick_event_all(vscsi);
+
+	scsi_scan_host(shost);
+	return 0;
+
+scsi_add_host_failed:
+	vdev->config->del_vqs(vdev);
+virtscsi_init_failed:
+	scsi_host_put(shost);
+	return err;
+}
+
+static void virtscsi_remove(struct virtio_device *vdev)
+{
+	struct Scsi_Host *shost = virtio_scsi_host(vdev);
+	struct virtio_scsi *vscsi = shost_priv(shost);
+
+	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
+		virtscsi_cancel_event_work(vscsi);
+
+	scsi_remove_host(shost);
+
+	unregister_hotcpu_notifier(&vscsi->nb);
+
+	virtscsi_remove_vqs(vdev);
+	scsi_host_put(shost);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int virtscsi_freeze(struct virtio_device *vdev)
+{
+	struct Scsi_Host *sh = virtio_scsi_host(vdev);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+
+	unregister_hotcpu_notifier(&vscsi->nb);
+	virtscsi_remove_vqs(vdev);
+	return 0;
+}
+
+static int virtscsi_restore(struct virtio_device *vdev)
+{
+	struct Scsi_Host *sh = virtio_scsi_host(vdev);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+	int err;
+
+	err = virtscsi_init(vdev, vscsi);
+	if (err)
+		return err;
+
+	err = register_hotcpu_notifier(&vscsi->nb);
+	if (err) {
+		vdev->config->del_vqs(vdev);
+		return err;
+	}
+
+	virtio_device_ready(vdev);
+
+	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
+		virtscsi_kick_event_all(vscsi);
+
+	return err;
+}
+#endif
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_SCSI, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static unsigned int features[] = {
+	VIRTIO_SCSI_F_HOTPLUG,
+	VIRTIO_SCSI_F_CHANGE,
+	VIRTIO_SCSI_F_T10_PI,
+};
+
+static struct virtio_driver virtio_scsi_driver = {
+	.feature_table = features,
+	.feature_table_size = ARRAY_SIZE(features),
+	.driver.name = KBUILD_MODNAME,
+	.driver.owner = THIS_MODULE,
+	.id_table = id_table,
+	.probe = virtscsi_probe,
+#ifdef CONFIG_PM_SLEEP
+	.freeze = virtscsi_freeze,
+	.restore = virtscsi_restore,
+#endif
+	.remove = virtscsi_remove,
+};
+
+static int __init init(void)
+{
+	int ret = -ENOMEM;
+
+	virtscsi_cmd_cache = KMEM_CACHE(virtio_scsi_cmd, 0);
+	if (!virtscsi_cmd_cache) {
+		pr_err("kmem_cache_create() for virtscsi_cmd_cache failed\n");
+		goto error;
+	}
+
+
+	virtscsi_cmd_pool =
+		mempool_create_slab_pool(VIRTIO_SCSI_MEMPOOL_SZ,
+					 virtscsi_cmd_cache);
+	if (!virtscsi_cmd_pool) {
+		pr_err("mempool_create() for virtscsi_cmd_pool failed\n");
+		goto error;
+	}
+	ret = register_virtio_driver(&virtio_scsi_driver);
+	if (ret < 0)
+		goto error;
+
+	return 0;
+
+error:
+	if (virtscsi_cmd_pool) {
+		mempool_destroy(virtscsi_cmd_pool);
+		virtscsi_cmd_pool = NULL;
+	}
+	if (virtscsi_cmd_cache) {
+		kmem_cache_destroy(virtscsi_cmd_cache);
+		virtscsi_cmd_cache = NULL;
+	}
+	return ret;
+}
+
+static void __exit fini(void)
+{
+	unregister_virtio_driver(&virtio_scsi_driver);
+	mempool_destroy(virtscsi_cmd_pool);
+	kmem_cache_destroy(virtscsi_cmd_cache);
+}
+module_init(init);
+module_exit(fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio SCSI HBA driver");
+MODULE_LICENSE("GPL");