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The LITMUS^RT kernel.

Bjoern Brandenburg

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5 -0400 virtio-scsi: introduce multiqueue support' href='/cgit/cgit.cgi/litmus-rt-budgetable-locks.git/.git/commit/drivers/scsi/virtio_scsi.c?h=update_litmus_2019&id=9141a4ca0d9551729573042660e9bce83a01e0af'>9141a4ca0d95

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/*
 * 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);


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