path: root/drivers/vhost/vringh.c

/*
 * Helpers for the host side of a virtio ring.
 *
 * Since these may be in userspace, we use (inline) accessors.
 */
#include <linux/module.h>
#include <linux/vringh.h>
#include <linux/virtio_ring.h>
#include <linux/kernel.h>
#include <linux/ratelimit.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/export.h>

static __printf(1,2) __cold void vringh_bad(const char *fmt, ...)
{
	static DEFINE_RATELIMIT_STATE(vringh_rs,
				      DEFAULT_RATELIMIT_INTERVAL,
				      DEFAULT_RATELIMIT_BURST);
	if (__ratelimit(&vringh_rs)) {
		va_list ap;
		va_start(ap, fmt);
		printk(KERN_NOTICE "vringh:");
		vprintk(fmt, ap);
		va_end(ap);
	}
}

/* Returns vring->num if empty, -ve on error. */
static inline int __vringh_get_head(const struct vringh *vrh,
				    int (*getu16)(u16 *val, const u16 *p),
				    u16 *last_avail_idx)
{
	u16 avail_idx, i, head;
	int err;

	err = getu16(&avail_idx, &vrh->vring.avail->idx);
	if (err) {
		vringh_bad("Failed to access avail idx at %p",
			   &vrh->vring.avail->idx);
		return err;
	}

	if (*last_avail_idx == avail_idx)
		return vrh->vring.num;

	/* Only get avail ring entries after they have been exposed by guest. */
	virtio_rmb(vrh->weak_barriers);

	i = *last_avail_idx & (vrh->vring.num - 1);

	err = getu16(&head, &vrh->vring.avail->ring[i]);
	if (err) {
		vringh_bad("Failed to read head: idx %d address %p",
			   *last_avail_idx, &vrh->vring.avail->ring[i]);
		return err;
	}

	if (head >= vrh->vring.num) {
		vringh_bad("Guest says index %u > %u is available",
			   head, vrh->vring.num);
		return -EINVAL;
	}

	(*last_avail_idx)++;
	return head;
}

/* Copy some bytes to/from the iovec.  Returns num copied. */
static inline ssize_t vringh_iov_xfer(struct vringh_kiov *iov,
				      void *ptr, size_t len,
				      int (*xfer)(void *addr, void *ptr,
						  size_t len))
{
	int err, done = 0;

	while (len && iov->i < iov->used) {
		size_t partlen;

		partlen = min(iov->iov[iov->i].iov_len, len);
		err = xfer(iov->iov[iov->i].iov_base, ptr, partlen);
		if (err)
			return err;
		done += partlen;
		len -= partlen;
		ptr += partlen;
		iov->consumed += partlen;
		iov->iov[iov->i].iov_len -= partlen;
		iov->iov[iov->i].iov_base += partlen;

		if (!iov->iov[iov->i].iov_len) {
			/* Fix up old iov element then increment. */
			iov->iov[iov->i].iov_len = iov->consumed;
			iov->iov[iov->i].iov_base -= iov->consumed;
			
			iov->consumed = 0;
			iov->i++;
		}
	}
	return done;
}

/* May reduce *len if range is shorter. */
static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len,
			       struct vringh_range *range,
			       bool (*getrange)(struct vringh *,
						u64, struct vringh_range *))
{
	if (addr < range->start || addr > range->end_incl) {
		if (!getrange(vrh, addr, range))
			return false;
	}
	BUG_ON(addr < range->start || addr > range->end_incl);

	/* To end of memory? */
	if (unlikely(addr + *len == 0)) {
		if (range->end_incl == -1ULL)
			return true;
		goto truncate;
	}

	/* Otherwise, don't wrap. */
	if (addr + *