diff --git a/include/qemu/iov.h b/include/qemu/iov.h
index bd9fd55b0a..72d4c559b4 100644
--- a/include/qemu/iov.h
+++ b/include/qemu/iov.h
@@ -31,11 +31,6 @@ size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt);
  * Number of bytes actually copied will be returned, which is
  *  min(bytes, iov_size(iov)-offset)
  * `Offset' must point to the inside of iovec.
- * It is okay to use very large value for `bytes' since we're
- * limited by the size of the iovec anyway, provided that the
- * buffer pointed to by buf has enough space.  One possible
- * such "large" value is -1 (sinice size_t is unsigned),
- * so specifying `-1' as `bytes' means 'up to the end of iovec'.
  */
 size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
                          size_t offset, const void *buf, size_t bytes);
@@ -76,7 +71,6 @@ iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
  * up to the end of it, will be filled with the specified value.
  * Function return actual number of bytes processed, which is
  * min(size, iov_size(iov) - offset).
- * Again, it is okay to use large value for `bytes' to mean "up to the end".
  */
 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
                   size_t offset, int fillc, size_t bytes);
diff --git a/tests/test-iov.c b/tests/test-iov.c
index fa3d75aee1..458ca25099 100644
--- a/tests/test-iov.c
+++ b/tests/test-iov.c
@@ -81,17 +81,17 @@ static void test_to_from_buf_1(void)
           * skip whole vector and process exactly 0 bytes */
 
          /* first set bytes [i..sz) to some "random" value */
-         n = iov_memset(iov, niov, 0, 0xff, -1);
+         n = iov_memset(iov, niov, 0, 0xff, sz);
          g_assert(n == sz);
 
          /* next copy bytes [i..sz) from ibuf to iovec */
-         n = iov_from_buf(iov, niov, i, ibuf + i, -1);
+         n = iov_from_buf(iov, niov, i, ibuf + i, sz - i);
          g_assert(n == sz - i);
 
          /* clear part of obuf */
          memset(obuf + i, 0, sz - i);
          /* and set this part of obuf to values from iovec */
-         n = iov_to_buf(iov, niov, i, obuf + i, -1);
+         n = iov_to_buf(iov, niov, i, obuf + i, sz - i);
          g_assert(n == sz - i);
 
          /* now compare resulting buffers */
@@ -109,7 +109,7 @@ static void test_to_from_buf_1(void)
               * with j in [i..sz]. */
 
              /* clear iovec */
-             n = iov_memset(iov, niov, 0, 0xff, -1);
+             n = iov_memset(iov, niov, 0, 0xff, sz);
              g_assert(n == sz);
 
              /* copy bytes [i..j) from ibuf to iovec */
@@ -225,7 +225,7 @@ static void test_io(void)
        for (i = 0; i <= sz; ++i) {
            for (j = i; j <= sz; ++j) {
                k = i;
-               iov_memset(iov, niov, 0, 0xff, -1);
+               iov_memset(iov, niov, 0, 0xff, sz);
                do {
                    s = g_test_rand_int_range(0, j - k + 1);
                    r = iov_recv(sv[0], iov, niov, k, s);