vhost: switch vhost get_indirect() to iov_iter, kill memcpy_fromiovec()

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/vhost/vhost.c

@@ -1125,6 +1125,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
 	struct vring_desc desc;
 	unsigned int i = 0, count, found = 0;
 	u32 len = vhost32_to_cpu(vq, indirect->len);
+	struct iov_iter from;
 	int ret;
 
 	/* Sanity check */
@@ -1142,6 +1143,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
 		vq_err(vq, "Translation failure %d in indirect.\n", ret);
 		return ret;
 	}
+	iov_iter_init(&from, READ, vq->indirect, ret, len);
 
 	/* We will use the result as an address to read from, so most
 	 * architectures only need a compiler barrier here. */
@@ -1164,8 +1166,8 @@ static int get_indirect(struct vhost_virtqueue *vq,
 			       i, count);
 			return -EINVAL;
 		}
-		if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
-					      vq->indirect, sizeof desc))) {
+		if (unlikely(copy_from_iter(&desc, sizeof(desc), &from) !=
+			     sizeof(desc))) {
 			vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
 			       i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
 			return -EINVAL;

include/linux/uio.h

@@ -135,7 +135,6 @@ static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 size_t csum_and_copy_to_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 
-int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
 int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
 			int offset, int len);
 int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,

lib/iovec.c

@@ -2,31 +2,6 @@
 #include <linux/export.h>
 #include <linux/uio.h>
 
-/*
- *	Copy iovec to kernel. Returns -EFAULT on error.
- *
- *	Note: this modifies the original iovec.
- */
-
-int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len)
-{
-	while (len > 0) {
-		if (iov->iov_len) {
-			int copy = min_t(unsigned int, len, iov->iov_len);
-			if (copy_from_user(kdata, iov->iov_base, copy))
-				return -EFAULT;
-			len -= copy;
-			kdata += copy;
-			iov->iov_base += copy;
-			iov->iov_len -= copy;
-		}
-		iov++;
-	}
-
-	return 0;
-}
-EXPORT_SYMBOL(memcpy_fromiovec);
-
 /*
  *	Copy kernel to iovec. Returns -EFAULT on error.
  */