1 files changed, 570 insertions, 0 deletions

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
new file mode 100644
index 000000000..68027e4fb
--- /dev/null
+++ b/net/9p/trans_xen.c
@@ -0,0 +1,570 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/fs/9p/trans_xen
+ *
+ * Xen transport layer.
+ *
+ * Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
+ */
+
+#include <xen/events.h>
+#include <xen/grant_table.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/interface/io/9pfs.h>
+
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
+#include <net/9p/transport.h>
+
+#define XEN_9PFS_NUM_RINGS 2
+#define XEN_9PFS_RING_ORDER 9
+#define XEN_9PFS_RING_SIZE(ring)  XEN_FLEX_RING_SIZE(ring->intf->ring_order)
+
+struct xen_9pfs_header {
+	uint32_t size;
+	uint8_t id;
+	uint16_t tag;
+
+	/* uint8_t sdata[]; */
+} __attribute__((packed));
+
+/* One per ring, more than one per 9pfs share */
+struct xen_9pfs_dataring {
+	struct xen_9pfs_front_priv *priv;
+
+	struct xen_9pfs_data_intf *intf;
+	grant_ref_t ref;
+	int evtchn;
+	int irq;
+	/* protect a ring from concurrent accesses */
+	spinlock_t lock;
+
+	struct xen_9pfs_data data;
+	wait_queue_head_t wq;
+	struct work_struct work;
+};
+
+/* One per 9pfs share */
+struct xen_9pfs_front_priv {
+	struct list_head list;
+	struct xenbus_device *dev;
+	char *tag;
+	struct p9_client *client;
+
+	int num_rings;
+	struct xen_9pfs_dataring *rings;
+};
+
+static LIST_HEAD(xen_9pfs_devs);
+static DEFINE_RWLOCK(xen_9pfs_lock);
+
+/* We don't currently allow canceling of requests */
+static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
+{
+	return 1;
+}
+
+static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
+{
+	struct xen_9pfs_front_priv *priv;
+
+	if (addr == NULL)
+		return -EINVAL;
+
+	read_lock(&xen_9pfs_lock);
+	list_for_each_entry(priv, &xen_9pfs_devs, list) {
+		if (!strcmp(priv->tag, addr)) {
+			priv->client = client;
+			read_unlock(&xen_9pfs_lock);
+			return 0;
+		}
+	}
+	read_unlock(&xen_9pfs_lock);
+	return -EINVAL;
+}
+
+static void p9_xen_close(struct p9_client *client)
+{
+	struct xen_9pfs_front_priv *priv;
+
+	read_lock(&xen_9pfs_lock);
+	list_for_each_entry(priv, &xen_9pfs_devs, list) {
+		if (priv->client == client) {
+			priv->client = NULL;
+			read_unlock(&xen_9pfs_lock);
+			return;
+		}
+	}
+	read_unlock(&xen_9pfs_lock);
+}
+
+static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
+{
+	RING_IDX cons, prod;
+
+	cons = ring->intf->out_cons;
+	prod = ring->intf->out_prod;
+	virt_mb();
+
+	return XEN_9PFS_RING_SIZE(ring) -
+		xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
+}
+
+static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
+{
+	struct xen_9pfs_front_priv *priv;
+	RING_IDX cons, prod, masked_cons, masked_prod;
+	unsigned long flags;
+	u32 size = p9_req->tc.size;
+	struct xen_9pfs_dataring *ring;
+	int num;
+
+	read_lock(&xen_9pfs_lock);
+	list_for_each_entry(priv, &xen_9pfs_devs, list) {
+		if (priv->client == client)
+			break;
+	}
+	read_unlock(&xen_9pfs_lock);
+	if (list_entry_is_head(priv, &xen_9pfs_devs, list))
+		return -EINVAL;
+
+	num = p9_req->tc.tag % priv->num_rings;
+	ring = &priv->rings[num];
+
+again:
+	while (wait_event_killable(ring->wq,
+				   p9_xen_write_todo(ring, size)) != 0)
+		;
+
+	spin_lock_irqsave(&ring->lock, flags);
+	cons = ring->intf->out_cons;
+	prod = ring->intf->out_prod;
+	virt_mb();
+
+	if (XEN_9PFS_RING_SIZE(ring) -
+	    xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
+		spin_unlock_irqrestore(&ring->lock, flags);
+		goto again;
+	}
+
+	masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
+	masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
+
+	xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
+			      &masked_prod, masked_cons,
+			      XEN_9PFS_RING_SIZE(ring));
+
+	WRITE_ONCE(p9_req->status, REQ_STATUS_SENT);
+	virt_wmb();			/* write ring before updating pointer */
+	prod += size;
+	ring->intf->out_prod = prod;
+	spin_unlock_irqrestore(&ring->lock, flags);
+	notify_remote_via_irq(ring->irq);
+	p9_req_put(client, p9_req);
+
+	return 0;
+}
+
+static void p9_xen_response(struct work_struct *work)
+{
+	struct xen_9pfs_front_priv *priv;
+	struct xen_9pfs_dataring *ring;
+	RING_IDX cons, prod, masked_cons, masked_prod;
+	struct xen_9pfs_header h;
+	struct p9_req_t *req;
+	int status;
+
+	ring = container_of(work, struct xen_9pfs_dataring, work);
+	priv = ring->priv;
+
+	while (1) {
+		cons = ring->intf->in_cons;
+		prod = ring->intf->in_prod;
+		virt_rmb();
+
+		if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
+		    sizeof(h)) {
+			notify_remote_via_irq(ring->irq);
+			return;
+		}
+
+		masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
+		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
+
+		/* First, read just the header */
+		xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
+				     masked_prod, &masked_cons,
+				     XEN_9PFS_RING_SIZE(ring));
+
+		req = p9_tag_lookup(priv->client, h.tag);
+		if (!req || req->status != REQ_STATUS_SENT) {
+			dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
+			cons += h.size;
+			virt_mb();
+			ring->intf->in_cons = cons;
+			continue;
+		}
+
+		if (h.size > req->rc.capacity) {
+			dev_warn(&priv->dev->dev,
+				 "requested packet size too big: %d for tag %d with capacity %zd\n",
+				 h.size, h.tag, req->rc.capacity);
+			WRITE_ONCE(req->status, REQ_STATUS_ERROR);
+			goto recv_error;
+		}
+
+		memcpy(&req->rc, &h, sizeof(h));
+		req->rc.offset = 0;
+
+		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
+		/* Then, read the whole packet (including the header) */
+		xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
+				     masked_prod, &masked_cons,
+				     XEN_9PFS_RING_SIZE(ring));
+
+recv_error:
+		virt_mb();
+		cons += h.size;
+		ring->intf->in_cons = cons;
+
+		status = (req->status != REQ_STATUS_ERROR) ?
+			REQ_STATUS_RCVD : REQ_STATUS_ERROR;
+
+		p9_client_cb(priv->client, req, status);
+	}
+}
+
+static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
+{
+	struct xen_9pfs_dataring *ring = r;
+
+	if (!ring || !ring->priv->client) {
+		/* ignore spurious interrupt */
+		return IRQ_HANDLED;
+	}
+
+	wake_up_interruptible(&ring->wq);
+	schedule_work(&ring->work);
+
+	return IRQ_HANDLED;
+}
+
+static struct p9_trans_module p9_xen_trans = {
+	.name = "xen",
+	.maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
+	.pooled_rbuffers = false,
+	.def = 1,
+	.create = p9_xen_create,
+	.close = p9_xen_close,
+	.request = p9_xen_request,
+	.cancel = p9_xen_cancel,
+	.owner = THIS_MODULE,
+};
+
+static const struct xenbus_device_id xen_9pfs_front_ids[] = {
+	{ "9pfs" },
+	{ "" }
+};
+
+static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
+{
+	int i, j;
+
+	write_lock(&xen_9pfs_lock);
+	list_del(&priv->list);
+	write_unlock(&xen_9pfs_lock);
+
+	for (i = 0; i < priv->num_rings; i++) {
+		struct xen_9pfs_dataring *ring = &priv->rings[i];
+
+		cancel_work_sync(&ring->work);
+
+		if (!priv->rings[i].intf)
+			break;
+		if (priv->rings[i].irq > 0)
+			unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
+		if (priv->rings[i].data.in) {
+			for (j = 0;
+			     j < (1 << priv->rings[i].intf->ring_order);
+			     j++) {
+				grant_ref_t ref;
+
+				ref = priv->rings[i].intf->ref[j];
+				gnttab_end_foreign_access(ref, NULL);
+			}
+			free_pages_exact(priv->rings[i].data.in,
+				   1UL << (priv->rings[i].intf->ring_order +
+					   XEN_PAGE_SHIFT));
+		}
+		gnttab_end_foreign_access(priv->rings[i].ref, NULL);
+		free_page((unsigned long)priv->rings[i].intf);
+	}
+	kfree(priv->rings);
+	kfree(priv->tag);
+	kfree(priv);
+}
+
+static int xen_9pfs_front_remove(struct xenbus_device *dev)
+{
+	struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
+
+	dev_set_drvdata(&dev->dev, NULL);
+	xen_9pfs_front_free(priv);
+	return 0;
+}
+
+static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
+					 struct xen_9pfs_dataring *ring,
+					 unsigned int order)
+{
+	int i = 0;
+	int ret = -ENOMEM;
+	void *bytes = NULL;
+
+	init_waitqueue_head(&ring->wq);
+	spin_lock_init(&ring->lock);
+	INIT_WORK(&ring->work, p9_xen_response);
+
+	ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
+	if (!ring->intf)
+		return ret;
+	ret = gnttab_grant_foreign_access(dev->otherend_id,
+					  virt_to_gfn(ring->intf), 0);
+	if (ret < 0)
+		goto out;
+	ring->ref = ret;
+	bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
+				  GFP_KERNEL | __GFP_ZERO);
+	if (!bytes) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	for (; i < (1 << order); i++) {
+		ret = gnttab_grant_foreign_access(
+				dev->otherend_id, virt_to_gfn(bytes) + i, 0);
+		if (ret < 0)
+			goto out;
+		ring->intf->ref[i] = ret;
+	}
+	ring->intf->ring_order = order;
+	ring->data.in = bytes;
+	ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
+
+	ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
+	if (ret)
+		goto out;
+	ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
+					      xen_9pfs_front_event_handler,
+					      0, "xen_9pfs-frontend", ring);
+	if (ring->irq >= 0)
+		return 0;
+
+	xenbus_free_evtchn(dev, ring->evtchn);
+	ret = ring->irq;
+out:
+	if (bytes) {
+		for (i--; i >= 0; i--)
+			gnttab_end_foreign_access(ring->intf->ref[i], NULL);
+		free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
+	}
+	gnttab_end_foreign_access(ring->ref, NULL);
+	free_page((unsigned long)ring->intf);
+	return ret;
+}
+
+static int xen_9pfs_front_init(struct xenbus_device *dev)
+{
+	int ret, i;
+	struct xenbus_transaction xbt;
+	struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
+	char *versions, *v;
+	unsigned int max_rings, max_ring_order, len = 0;
+
+	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
+	if (IS_ERR(versions))
+		return PTR_ERR(versions);
+	for (v = versions; *v; v++) {
+		if (simple_strtoul(v, &v, 10) == 1) {
+			v = NULL;
+			break;
+		}
+	}
+	if (v) {
+		kfree(versions);
+		return -EINVAL;
+	}
+	kfree(versions);
+	max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
+	if (max_rings < XEN_9PFS_NUM_RINGS)
+		return -EINVAL;
+	max_ring_order = xenbus_read_unsigned(dev->otherend,
+					      "max-ring-page-order", 0);
+	if (max_ring_order > XEN_9PFS_RING_ORDER)
+		max_ring_order = XEN_9PFS_RING_ORDER;
+	if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
+		p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
+
+	priv->num_rings = XEN_9PFS_NUM_RINGS;
+	priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
+			      GFP_KERNEL);
+	if (!priv->rings) {
+		kfree(priv);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < priv->num_rings; i++) {
+		priv->rings[i].priv = priv;
+		ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
+						    max_ring_order);
+		if (ret < 0)
+			goto error;
+	}
+
+ again:
+	ret = xenbus_transaction_start(&xbt);
+	if (ret) {
+		xenbus_dev_fatal(dev, ret, "starting transaction");
+		goto error;
+	}
+	ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
+	if (ret)
+		goto error_xenbus;
+	ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
+			    priv->num_rings);
+	if (ret)
+		goto error_xenbus;
+	for (i = 0; i < priv->num_rings; i++) {
+		char str[16];
+
+		BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
+		sprintf(str, "ring-ref%d", i);
+		ret = xenbus_printf(xbt, dev->nodename, str, "%d",
+				    priv->rings[i].ref);
+		if (ret)
+			goto error_xenbus;
+
+		sprintf(str, "event-channel-%d", i);
+		ret = xenbus_printf(xbt, dev->nodename, str, "%u",
+				    priv->rings[i].evtchn);
+		if (ret)
+			goto error_xenbus;
+	}
+	priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
+	if (IS_ERR(priv->tag)) {
+		ret = PTR_ERR(priv->tag);
+		goto error_xenbus;
+	}
+	ret = xenbus_transaction_end(xbt, 0);
+	if (ret) {
+		if (ret == -EAGAIN)
+			goto again;
+		xenbus_dev_fatal(dev, ret, "completing transaction");
+		goto error;
+	}
+
+	return 0;
+
+ error_xenbus:
+	xenbus_transaction_end(xbt, 1);
+	xenbus_dev_fatal(dev, ret, "writing xenstore");
+ error:
+	xen_9pfs_front_free(priv);
+	return ret;
+}
+
+static int xen_9pfs_front_probe(struct xenbus_device *dev,
+				const struct xenbus_device_id *id)
+{
+	struct xen_9pfs_front_priv *priv = NULL;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->dev = dev;
+	dev_set_drvdata(&dev->dev, priv);
+
+	write_lock(&xen_9pfs_lock);
+	list_add_tail(&priv->list, &xen_9pfs_devs);
+	write_unlock(&xen_9pfs_lock);
+
+	return 0;
+}
+
+static int xen_9pfs_front_resume(struct xenbus_device *dev)
+{
+	dev_warn(&dev->dev, "suspend/resume unsupported\n");
+	return 0;
+}
+
+static void xen_9pfs_front_changed(struct xenbus_device *dev,
+				   enum xenbus_state backend_state)
+{
+	switch (backend_state) {
+	case XenbusStateReconfiguring:
+	case XenbusStateReconfigured:
+	case XenbusStateInitialising:
+	case XenbusStateInitialised:
+	case XenbusStateUnknown:
+		break;
+
+	case XenbusStateInitWait:
+		if (!xen_9pfs_front_init(dev))
+			xenbus_switch_state(dev, XenbusStateInitialised);
+		break;
+
+	case XenbusStateConnected:
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		fallthrough;	/* Missed the backend's CLOSING state */
+	case XenbusStateClosing:
+		xenbus_frontend_closed(dev);
+		break;
+	}
+}
+
+static struct xenbus_driver xen_9pfs_front_driver = {
+	.ids = xen_9pfs_front_ids,
+	.probe = xen_9pfs_front_probe,
+	.remove = xen_9pfs_front_remove,
+	.resume = xen_9pfs_front_resume,
+	.otherend_changed = xen_9pfs_front_changed,
+};
+
+static int __init p9_trans_xen_init(void)
+{
+	int rc;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	pr_info("Initialising Xen transport for 9pfs\n");
+
+	v9fs_register_trans(&p9_xen_trans);
+	rc = xenbus_register_frontend(&xen_9pfs_front_driver);
+	if (rc)
+		v9fs_unregister_trans(&p9_xen_trans);
+
+	return rc;
+}
+module_init(p9_trans_xen_init);
+MODULE_ALIAS_9P("xen");
+
+static void __exit p9_trans_xen_exit(void)
+{
+	v9fs_unregister_trans(&p9_xen_trans);
+	return xenbus_unregister_driver(&xen_9pfs_front_driver);
+}
+module_exit(p9_trans_xen_exit);
+
+MODULE_ALIAS("xen:9pfs");
+MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
+MODULE_DESCRIPTION("Xen Transport for 9P");
+MODULE_LICENSE("GPL");