Merge tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

Pull virtio & lguest updates from Rusty Russell:
 "Lots of virtio work which wasn't quite ready for last merge window.

  Plus I dived into lguest again, reworking the pagetable code so we can
  move the switcher page: our fixmaps sometimes take more than 2MB now..."

Ugh.  Annoying conflicts with the tcm_vhost -> vhost_scsi rename.
Hopefully correctly resolved.

* tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (57 commits)
  caif_virtio: Remove bouncing email addresses
  lguest: improve code readability in lg_cpu_start.
  virtio-net: fill only rx queues which are being used
  lguest: map Switcher below fixmap.
  lguest: cache last cpu we ran on.
  lguest: map Switcher text whenever we allocate a new pagetable.
  lguest: don't share Switcher PTE pages between guests.
  lguest: expost switcher_pages array (as lg_switcher_pages).
  lguest: extract shadow PTE walking / allocating.
  lguest: make check_gpte et. al return bool.
  lguest: assume Switcher text is a single page.
  lguest: rename switcher_page to switcher_pages.
  lguest: remove RESERVE_MEM constant.
  lguest: check vaddr not pgd for Switcher protection.
  lguest: prepare to make SWITCHER_ADDR a variable.
  virtio: console: replace EMFILE with EBUSY for already-open port
  virtio-scsi: reset virtqueue affinity when doing cpu hotplug
  virtio-scsi: introduce multiqueue support
  virtio-scsi: push vq lock/unlock into virtscsi_vq_done
  virtio-scsi: pass struct virtio_scsi to virtqueue completion function
  ...

1 files changed, 346 insertions, 141 deletions

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 3449a1f8c656..2168258fb2c3 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -13,6 +13,8 @@
  *
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/mempool.h>
@@ -20,12 +22,14 @@
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.h>
 #include <linux/virtio_scsi.h>
+#include <linux/cpu.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_device.h>
 #include <scsi/scsi_cmnd.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 {
@@ -57,27 +61,61 @@ struct virtio_scsi_vq {
 	struct virtqueue *vq;
 };
 
-/* Per-target queue state */
+/*
+ * 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).
+ *
+ * An interesting effect of this policy is that only writes to req_vq need to
+ * take the tgt_lock.  Read can be done outside the lock because:
+ *
+ * - writes of req_vq only occur when atomic_inc_return(&tgt->reqs) returns 1.
+ *   In that case, no other CPU is reading req_vq: even if they were in
+ *   virtscsi_queuecommand_multi, they would be spinning on tgt_lock.
+ *
+ * - reads of req_vq only occur when the target is not idle (reqs != 0).
+ *   A CPU that enters virtscsi_queuecommand_multi will not modify req_vq.
+ *
+ * Similarly, decrements of reqs are never concurrent with writes of req_vq.
+ * Thus they can happen outside the tgt_lock, provided of course we make reqs
+ * an atomic_t.
+ */
 struct virtio_scsi_target_state {
-	/* Protects sg.  Lock hierarchy is tgt_lock -> vq_lock.  */
+	/* This spinlock never held at the same time as vq_lock. */
 	spinlock_t tgt_lock;
 
-	/* For sglist construction when adding commands to the virtqueue.  */
-	struct scatterlist sg[];
+	/* 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;
 
-	struct virtio_scsi_vq ctrl_vq;
-	struct virtio_scsi_vq event_vq;
-	struct virtio_scsi_vq req_vq;
-
 	/* Get some buffers ready for event vq */
 	struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
 
-	struct virtio_scsi_target_state *tgt[];
+	u32 num_queues;
+
+	/* If the affinity hint is set for virtqueues */
+	bool affinity_hint_set;
+
+	/* CPU hotplug notifier */
+	struct notifier_block nb;
+
+	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;
@@ -107,11 +145,13 @@ static void virtscsi_compute_resid(struct scsi_cmnd *sc, u32 resid)
  *
  * Called with vq_lock held.
  */
-static void virtscsi_complete_cmd(void *buf)
+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",
@@ -166,32 +206,71 @@ static void virtscsi_complete_cmd(void *buf)
 
 	mempool_free(cmd, virtscsi_cmd_pool);
 	sc->scsi_done(sc);
+
+	atomic_dec(&tgt->reqs);
 }
 
-static void virtscsi_vq_done(struct virtqueue *vq, void (*fn)(void *buf))
+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(buf);
+			fn(vscsi, buf);
 	} 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);
-	unsigned long flags;
+	int index = vq->index - VIRTIO_SCSI_VQ_BASE;
+	struct virtio_scsi_vq *req_vq = &vscsi->req_vqs[index];
 
-	spin_lock_irqsave(&vscsi->req_vq.vq_lock, flags);
-	virtscsi_vq_done(vq, virtscsi_complete_cmd);
-	spin_unlock_irqrestore(&vscsi->req_vq.vq_lock, flags);
+	/*
+	 * Read req_vq before decrementing the reqs field in
+	 * virtscsi_complete_cmd.
+	 *
+	 * With barriers:
+	 *
+	 * 	CPU #0			virtscsi_queuecommand_multi (CPU #1)
+	 * 	------------------------------------------------------------
+	 * 	lock vq_lock
+	 * 	read req_vq
+	 * 	read reqs (reqs = 1)
+	 * 	write reqs (reqs = 0)
+	 * 				increment reqs (reqs = 1)
+	 * 				write req_vq
+	 *
+	 * Possible reordering without barriers:
+	 *
+	 * 	CPU #0			virtscsi_queuecommand_multi (CPU #1)
+	 * 	------------------------------------------------------------
+	 * 	lock vq_lock
+	 * 	read reqs (reqs = 1)
+	 * 	write reqs (reqs = 0)
+	 * 				increment reqs (reqs = 1)
+	 * 				write req_vq
+	 * 	read (wrong) req_vq
+	 *
+	 * We do not need a full smp_rmb, because req_vq is required to get
+	 * to tgt->reqs: tgt is &vscsi->tgt[sc->device->id], where sc is stored
+	 * in the virtqueue as the user token.
+	 */
+	smp_read_barrier_depends();
+
+	virtscsi_vq_done(vscsi, req_vq, virtscsi_complete_cmd);
 };
 
-static void virtscsi_complete_free(void *buf)
+static void virtscsi_complete_free(struct virtio_scsi *vscsi, void *buf)
 {
 	struct virtio_scsi_cmd *cmd = buf;
 
@@ -205,11 +284,8 @@ static void virtscsi_ctrl_done(struct virtqueue *vq)
 {
 	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
 	struct virtio_scsi *vscsi = shost_priv(sh);
-	unsigned long flags;
 
-	spin_lock_irqsave(&vscsi->ctrl_vq.vq_lock, flags);
-	virtscsi_vq_done(vq, virtscsi_complete_free);
-	spin_unlock_irqrestore(&vscsi->ctrl_vq.vq_lock, flags);
+	virtscsi_vq_done(vscsi, &vscsi->ctrl_vq, virtscsi_complete_free);
 };
 
 static int virtscsi_kick_event(struct virtio_scsi *vscsi,
@@ -223,8 +299,8 @@ static int virtscsi_kick_event(struct virtio_scsi *vscsi,
 
 	spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
 
-	err = virtqueue_add_buf(vscsi->event_vq.vq, &sg, 0, 1, event_node,
-				GFP_ATOMIC);
+	err = virtqueue_add_inbuf(vscsi->event_vq.vq, &sg, 1, event_node,
+				  GFP_ATOMIC);
 	if (!err)
 		virtqueue_kick(vscsi->event_vq.vq);
 
@@ -254,7 +330,7 @@ static void virtscsi_cancel_event_work(struct virtio_scsi *vscsi)
 }
 
 static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
-						struct virtio_scsi_event *event)
+					    struct virtio_scsi_event *event)
 {
 	struct scsi_device *sdev;
 	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
@@ -332,7 +408,7 @@ static void virtscsi_handle_event(struct work_struct *work)
 	virtscsi_kick_event(vscsi, event_node);
 }
 
-static void virtscsi_complete_event(void *buf)
+static void virtscsi_complete_event(struct virtio_scsi *vscsi, void *buf)
 {
 	struct virtio_scsi_event_node *event_node = buf;
 
@@ -344,82 +420,65 @@ static void virtscsi_event_done(struct virtqueue *vq)
 {
 	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
 	struct virtio_scsi *vscsi = shost_priv(sh);
-	unsigned long flags;
 
-	spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
-	virtscsi_vq_done(vq, virtscsi_complete_event);
-	spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
+	virtscsi_vq_done(vscsi, &vscsi->event_vq, virtscsi_complete_event);
 };
 
-static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx,
-			     struct scsi_data_buffer *sdb)
-{
-	struct sg_table *table = &sdb->table;
-	struct scatterlist *sg_elem;
-	unsigned int idx = *p_idx;
-	int i;
-
-	for_each_sg(table->sgl, sg_elem, table->nents, i)
-		sg[idx++] = *sg_elem;
-
-	*p_idx = idx;
-}
-
 /**
- * virtscsi_map_cmd - map a scsi_cmd to a virtqueue scatterlist
- * @vscsi	: virtio_scsi state
+ * virtscsi_add_cmd - add a virtio_scsi_cmd to a virtqueue
+ * @vq		: the struct virtqueue we're talking about
  * @cmd		: command structure
- * @out_num	: number of read-only elements
- * @in_num	: number of write-only elements
  * @req_size	: size of the request buffer
  * @resp_size	: size of the response buffer
- *
- * Called with tgt_lock held.
+ * @gfp	: flags to use for memory allocations
  */
-static void virtscsi_map_cmd(struct virtio_scsi_target_state *tgt,
-			     struct virtio_scsi_cmd *cmd,
-			     unsigned *out_num, unsigned *in_num,
-			     size_t req_size, size_t resp_size)
+static int virtscsi_add_cmd(struct virtqueue *vq,
+			    struct virtio_scsi_cmd *cmd,
+			    size_t req_size, size_t resp_size, gfp_t gfp)
 {
 	struct scsi_cmnd *sc = cmd->sc;
-	struct scatterlist *sg = tgt->sg;
-	unsigned int idx = 0;
+	struct scatterlist *sgs[4], 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_set_buf(&sg[idx++], &cmd->req, req_size);
+	sg_init_one(&req, &cmd->req, req_size);
+	sgs[out_num++] = &req;
 
 	/* Data-out buffer.  */
-	if (sc && sc->sc_data_direction != DMA_FROM_DEVICE)
-		virtscsi_map_sgl(sg, &idx, scsi_out(sc));
-
-	*out_num = idx;
+	if (out)
+		sgs[out_num++] = out->sgl;
 
 	/* Response header.  */
-	sg_set_buf(&sg[idx++], &cmd->resp, resp_size);
+	sg_init_one(&resp, &cmd->resp, resp_size);
+	sgs[out_num + in_num++] = &resp;
 
 	/* Data-in buffer */
-	if (sc && sc->sc_data_direction != DMA_TO_DEVICE)
-		virtscsi_map_sgl(sg, &idx, scsi_in(sc));
+	if (in)
+		sgs[out_num + in_num++] = in->sgl;
 
-	*in_num = idx - *out_num;
+	return virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, gfp);
 }
 
-static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt,
-			     struct virtio_scsi_vq *vq,
+static int virtscsi_kick_cmd(struct virtio_scsi_vq *vq,
 			     struct virtio_scsi_cmd *cmd,
 			     size_t req_size, size_t resp_size, gfp_t gfp)
 {
-	unsigned int out_num, in_num;
 	unsigned long flags;
 	int err;
 	bool needs_kick = false;
 
-	spin_lock_irqsave(&tgt->tgt_lock, flags);
-	virtscsi_map_cmd(tgt, cmd, &out_num, &in_num, req_size, resp_size);
-
-	spin_lock(&vq->vq_lock);
-	err = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp);
-	spin_unlock(&tgt->tgt_lock);
+	spin_lock_irqsave(&vq->vq_lock, flags);
+	err = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size, gfp);
 	if (!err)
 		needs_kick = virtqueue_kick_prepare(vq->vq);
 
@@ -430,10 +489,10 @@ static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt,
 	return err;
 }
 
-static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
+static int virtscsi_queuecommand(struct virtio_scsi *vscsi,
+				 struct virtio_scsi_vq *req_vq,
+				 struct scsi_cmnd *sc)
 {
-	struct virtio_scsi *vscsi = shost_priv(sh);
-	struct virtio_scsi_target_state *tgt = vscsi->tgt[sc->device->id];
 	struct virtio_scsi_cmd *cmd;
 	int ret;
 
@@ -467,7 +526,7 @@ static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
 	BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);
 	memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);
 
-	if (virtscsi_kick_cmd(tgt, &vscsi->req_vq, cmd,
+	if (virtscsi_kick_cmd(req_vq, cmd,
 			      sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
 			      GFP_ATOMIC) == 0)
 		ret = 0;
@@ -478,14 +537,62 @@ out:
 	return ret;
 }
 
+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(struct virtio_scsi *vscsi,
+					       struct virtio_scsi_target_state *tgt)
+{
+	struct virtio_scsi_vq *vq;
+	unsigned long flags;
+	u32 queue_num;
+
+	spin_lock_irqsave(&tgt->tgt_lock, flags);
+
+	/*
+	 * The memory barrier after atomic_inc_return matches
+	 * the smp_read_barrier_depends() in virtscsi_req_done.
+	 */
+	if (atomic_inc_return(&tgt->reqs) > 1)
+		vq = ACCESS_ONCE(tgt->req_vq);
+	else {
+		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];
+	}
+
+	spin_unlock_irqrestore(&tgt->tgt_lock, 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 = 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);
-	struct virtio_scsi_target_state *tgt = vscsi->tgt[cmd->sc->device->id];
 	int ret = FAILED;
 
 	cmd->comp = &comp;
-	if (virtscsi_kick_cmd(tgt, &vscsi->ctrl_vq, cmd,
+	if (virtscsi_kick_cmd(&vscsi->ctrl_vq, cmd,
 			      sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
 			      GFP_NOIO) < 0)
 		goto out;
@@ -547,18 +654,57 @@ static int virtscsi_abort(struct scsi_cmnd *sc)
 	return virtscsi_tmf(vscsi, cmd);
 }
 
-static struct scsi_host_template virtscsi_host_template = {
+static int virtscsi_target_alloc(struct scsi_target *starget)
+{
+	struct virtio_scsi_target_state *tgt =
+				kmalloc(sizeof(*tgt), GFP_KERNEL);
+	if (!tgt)
+		return -ENOMEM;
+
+	spin_lock_init(&tgt->tgt_lock);
+	atomic_set(&tgt->reqs, 0);
+	tgt->req_vq = NULL;
+
+	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,
+	.queuecommand = virtscsi_queuecommand_single,
+	.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,
+};
+
+static struct scsi_host_template virtscsi_host_template_multi = {
 	.module = THIS_MODULE,
 	.name = "Virtio SCSI HBA",
 	.proc_name = "virtio_scsi",
-	.queuecommand = virtscsi_queuecommand,
 	.this_id = -1,
+	.queuecommand = virtscsi_queuecommand_multi,
 	.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,
 };
 
 #define virtscsi_config_get(vdev, fld) \
@@ -578,29 +724,69 @@ static struct scsi_host_template virtscsi_host_template = {
 				  &__val, sizeof(__val)); \
 	})
 
-static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
-			     struct virtqueue *vq)
+static void __virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
 {
-	spin_lock_init(&virtscsi_vq->vq_lock);
-	virtscsi_vq->vq = vq;
+	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 - VIRTIO_SCSI_VQ_BASE; i++)
+			virtqueue_set_affinity(vscsi->req_vqs[i].vq, -1);
+
+		vscsi->affinity_hint_set = false;
+	}
 }
 
-static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
-	struct virtio_device *vdev, int sg_elems)
+static void virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
 {
-	struct virtio_scsi_target_state *tgt;
-	gfp_t gfp_mask = GFP_KERNEL;
-
-	/* We need extra sg elements at head and tail.  */
-	tgt = kmalloc(sizeof(*tgt) + sizeof(tgt->sg[0]) * (sg_elems + 2),
-		      gfp_mask);
+	get_online_cpus();
+	__virtscsi_set_affinity(vscsi, affinity);
+	put_online_cpus();
+}
 
-	if (!tgt)
-		return NULL;
+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;
+}
 
-	spin_lock_init(&tgt->tgt_lock);
-	sg_init_table(tgt->sg, sg_elems + 2);
-	return tgt;
+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_scan(struct virtio_device *vdev)
@@ -614,46 +800,56 @@ static void virtscsi_remove_vqs(struct virtio_device *vdev)
 {
 	struct Scsi_Host *sh = virtio_scsi_host(vdev);
 	struct virtio_scsi *vscsi = shost_priv(sh);
-	u32 i, num_targets;
+
+	virtscsi_set_affinity(vscsi, false);
 
 	/* Stop all the virtqueues. */
 	vdev->config->reset(vdev);
 
-	num_targets = sh->max_id;
-	for (i = 0; i < num_targets; i++) {
-		kfree(vscsi->tgt[i]);
-		vscsi->tgt[i] = NULL;
-	}
-
 	vdev->config->del_vqs(vdev);
 }
 
 static int virtscsi_init(struct virtio_device *vdev,
-			 struct virtio_scsi *vscsi, int num_targets)
+			 struct virtio_scsi *vscsi)
 {
 	int err;
-	struct virtqueue *vqs[3];
-	u32 i, sg_elems;
+	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;
+	}
 
-	vq_callback_t *callbacks[] = {
-		virtscsi_ctrl_done,
-		virtscsi_event_done,
-		virtscsi_req_done
-	};
-	const char *names[] = {
-		"control",
-		"event",
-		"request"
-	};
+	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, 3, vqs, callbacks, names);
+	err = vdev->config->find_vqs(vdev, num_vqs, vqs, callbacks, names);
 	if (err)
-		return err;
+		goto out;
 
 	virtscsi_init_vq(&vscsi->ctrl_vq, vqs[0]);
 	virtscsi_init_vq(&vscsi->event_vq, vqs[1]);
-	virtscsi_init_vq(&vscsi->req_vq, vqs[2]);
+	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);
@@ -661,19 +857,12 @@ static int virtscsi_init(struct virtio_device *vdev,
 	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
 		virtscsi_kick_event_all(vscsi);
 
-	/* We need to know how many segments before we allocate.  */
-	sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
-
-	for (i = 0; i < num_targets; i++) {
-		vscsi->tgt[i] = virtscsi_alloc_tgt(vdev, sg_elems);
-		if (!vscsi->tgt[i]) {
-			err = -ENOMEM;
-			goto out;
-		}
-	}
 	err = 0;
 
 out:
+	kfree(names);
+	kfree(callbacks);
+	kfree(vqs);
 	if (err)
 		virtscsi_remove_vqs(vdev);
 	return err;
@@ -686,13 +875,21 @@ static int virtscsi_probe(struct virtio_device *vdev)
 	int err;
 	u32 sg_elems, num_targets;
 	u32 cmd_per_lun;
+	u32 num_queues;
+	struct scsi_host_template *hostt;
+
+	/* We need to know how many queues before we allocate. */
+	num_queues = virtscsi_config_get(vdev, num_queues) ? : 1;
 
-	/* Allocate memory and link the structs together.  */
 	num_targets = virtscsi_config_get(vdev, max_target) + 1;
-	shost = scsi_host_alloc(&virtscsi_host_template,
-		sizeof(*vscsi)
-		+ num_targets * sizeof(struct virtio_scsi_target_state));
 
+	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;
 
@@ -700,12 +897,20 @@ static int virtscsi_probe(struct virtio_device *vdev)
 	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, num_targets);
+	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;
@@ -743,6 +948,8 @@ static void virtscsi_remove(struct virtio_device *vdev)
 
 	scsi_remove_host(shost);
 
+	unregister_hotcpu_notifier(&vscsi->nb);
+
 	virtscsi_remove_vqs(vdev);
 	scsi_host_put(shost);
 }
@@ -759,7 +966,7 @@ static int virtscsi_restore(struct virtio_device *vdev)
 	struct Scsi_Host *sh = virtio_scsi_host(vdev);
 	struct virtio_scsi *vscsi = shost_priv(sh);
 
-	return virtscsi_init(vdev, vscsi, sh->max_id);
+	return virtscsi_init(vdev, vscsi);
 }
 #endif
 
@@ -794,8 +1001,7 @@ static int __init init(void)
 
 	virtscsi_cmd_cache = KMEM_CACHE(virtio_scsi_cmd, 0);
 	if (!virtscsi_cmd_cache) {
-		printk(KERN_ERR "kmem_cache_create() for "
-				"virtscsi_cmd_cache failed\n");
+		pr_err("kmem_cache_create() for virtscsi_cmd_cache failed\n");
 		goto error;
 	}
 
@@ -804,8 +1010,7 @@ static int __init init(void)
 		mempool_create_slab_pool(VIRTIO_SCSI_MEMPOOL_SZ,
 					 virtscsi_cmd_cache);
 	if (!virtscsi_cmd_pool) {
-		printk(KERN_ERR "mempool_create() for"
-				"virtscsi_cmd_pool failed\n");
+		pr_err("mempool_create() for virtscsi_cmd_pool failed\n");
 		goto error;
 	}
 	ret = register_virtio_driver(&virtio_scsi_driver);