path: root/net/vmw_vsock/virtio_transport.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * virtio transport for vsock
 *
 * Copyright (C) 2013-2015 Red Hat, Inc.
 * Author: Asias He <asias@redhat.com>
 *         Stefan Hajnoczi <stefanha@redhat.com>
 *
 * Some of the code is take from Gerd Hoffmann <kraxel@redhat.com>'s
 * early virtio-vsock proof-of-concept bits.
 */
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/atomic.h>
#include <linux/virtio.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_config.h>
#include <linux/virtio_vsock.h>
#include <net/sock.h>
#include <linux/mutex.h>
#include <net/af_vsock.h>

static struct workqueue_struct *virtio_vsock_workqueue;
static struct virtio_vsock __rcu *the_virtio_vsock;
static DEFINE_MUTEX(the_virtio_vsock_mutex); /* protects the_virtio_vsock */
static struct virtio_transport virtio_transport; /* forward declaration */

struct virtio_vsock {
	struct virtio_device *vdev;
	struct virtqueue *vqs[VSOCK_VQ_MAX];

	/* Virtqueue processing is deferred to a workqueue */
	struct work_struct tx_work;
	struct work_struct rx_work;
	struct work_struct event_work;

	/* The following fields are protected by tx_lock.  vqs[VSOCK_VQ_TX]
	 * must be accessed with tx_lock held.
	 */
	struct mutex tx_lock;
	bool tx_run;

	struct work_struct send_pkt_work;
	struct sk_buff_head send_pkt_queue;

	atomic_t queued_replies;

	/* The following fields are protected by rx_lock.  vqs[VSOCK_VQ_RX]
	 * must be accessed with rx_lock held.
	 */
	struct mutex rx_lock;
	bool rx_run;
	int rx_buf_nr;
	int rx_buf_max_nr;

	/* The following fields are protected by event_lock.
	 * vqs[VSOCK_VQ_EVENT] must be accessed with event_lock held.
	 */
	struct mutex event_lock;
	bool event_run;
	struct virtio_vsock_event event_list[8];

	u32 guest_cid;
	bool seqpacket_allow;

	/* These fields are used only in tx path in function
	 * 'virtio_transport_send_pkt_work()', so to save
	 * stack space in it, place both of them here. Each
	 * pointer from 'out_sgs' points to the corresponding
	 * element in 'out_bufs' - this is initialized in
	 * 'virtio_vsock_probe()'. Both fields are protected
	 * by 'tx_lock'. +1 is needed for packet header.
	 */
	struct scatterlist *out_sgs[MAX_SKB_FRAGS + 1];
	struct scatterlist out_bufs[MAX_SKB_FRAGS + 1];
};

static u32 virtio_transport_get_local_cid(void)
{
	struct virtio_vsock *vsock;
	u32 ret;

	rcu_read_lock();
	vsock = rcu_dereference(the_virtio_vsock);
	if (!vsock) {
		ret = VMADDR_CID_ANY;
		goto out_rcu;
	}

	ret = vsock->guest_cid;
out_rcu:
	rcu_read_unlock();
	return ret;
}

/* Caller need to hold vsock->tx_lock on vq */
static int virtio_transport_send_skb(struct sk_buff *skb, struct virtqueue *vq,
				     struct virtio_vsock *vsock, gfp_t gfp)
{
	int ret, in_sg = 0, out_sg = 0;
	struct scatterlist **sgs;

	sgs = vsock->out_sgs;
	sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
		    sizeof(*virtio_vsock_hdr(skb)));
	out_sg++;

	if (!skb_is_nonlinear(skb)) {
		if (skb->len > 0) {
			sg_init_one(sgs[out_sg], skb->data, skb->len);
			out_sg++;
		}
	} else {
		struct skb_shared_info *si;
		int i;

		/* If skb is nonlinear, then its buffer must contain
		 * only header and nothing more. Data is stored in
		 * the fragged part.
		 */
		WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));

		si = skb_shinfo(skb);

		for (i = 0; i < si->nr_frags; i++) {
			skb_frag_t *skb_frag = &si->frags[i];
			void *va;

			/* We will use 'page_to_virt()' for the userspace page
			 * here, because virtio or dma-mapping layers will call
			 * 'virt_to_phys()' later to fill the buffer descriptor.
			 * We don't touch memory at "virtual" address of this page.
			 */
			va = page_to_virt(skb_frag_page(skb_frag));
			sg_init_one(sgs[out_sg],
				    va + skb_frag_off(skb_frag),
				    skb_frag_size(skb_frag));
			out_sg++;
		}
	}

	ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, gfp);
	/* Usually this means that there is no more space available in
	 * the vq
	 */
	if (ret < 0)
		return ret;

	virtio_transport_deliver_tap_pkt(skb);
	return 0;
}

static void
virtio_transport_send_pkt_work(struct work_struct *work)
{
	struct virtio_vsock *vsock =
		container_of(work, struct virtio_vsock, send_pkt_work);
	struct virtqueue *vq;
	bool added = false;
	bool restart_rx = false;

	mutex_lock(&vsock->tx_lock);

	if (!vsock->tx_run)
		goto out;

	vq = vsock->vqs[VSOCK_VQ_TX];

	for (;;) {
		struct sk_buff *skb;
		bool reply;
		int ret;

		skb = virtio_vsock_skb_dequeue(&vsock->send_pkt_queue);
		if (!skb)