diff --git a/block/nbd.c b/block/nbd.c
index 161b299..9919acc 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -194,7 +194,7 @@ static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request,
                             nbd_have_request, NULL, s);
     rc = nbd_send_request(s->sock, request);
     if (rc != -1 && iov) {
-        ret = qemu_co_sendv(s->sock, iov, request->len, offset);
+        ret = qemu_co_sendv(s->sock, iov, offset, request->len);
         if (ret != request->len) {
             errno = -EIO;
             rc = -1;
@@ -221,7 +221,7 @@ static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request,
         reply->error = EIO;
     } else {
         if (iov && reply->error == 0) {
-            ret = qemu_co_recvv(s->sock, iov, request->len, offset);
+            ret = qemu_co_recvv(s->sock, iov, offset, request->len);
             if (ret != request->len) {
                 reply->error = EIO;
             }
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 00276f6f..1083f27 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -657,8 +657,8 @@ static void coroutine_fn aio_read_response(void *opaque)
         }
         break;
     case AIOCB_READ_UDATA:
-        ret = qemu_co_recvv(fd, acb->qiov->iov, rsp.data_length,
-                            aio_req->iov_offset);
+        ret = qemu_co_recvv(fd, acb->qiov->iov,
+                            aio_req->iov_offset, rsp.data_length);
         if (ret < 0) {
             error_report("failed to get the data, %s", strerror(errno));
             goto out;
@@ -924,7 +924,7 @@ static int coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
     }
 
     if (wlen) {
-        ret = qemu_co_sendv(s->fd, iov, wlen, aio_req->iov_offset);
+        ret = qemu_co_sendv(s->fd, iov, aio_req->iov_offset, wlen);
         if (ret < 0) {
             qemu_co_mutex_unlock(&s->lock);
             error_report("failed to send a data, %s", strerror(errno));
diff --git a/qemu-common.h b/qemu-common.h
index b01d84c..eae1bde 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -207,6 +207,8 @@ int qemu_pipe(int pipefd[2]);
  */
 ssize_t qemu_sendv_recvv(int sockfd, struct iovec *iov,
                          size_t offset, size_t bytes, bool do_sendv);
+/* these are basically unused now when everything
+ * switched is using coroutine versions */
 #define qemu_recvv(sockfd, iov, offset, bytes) \
   qemu_sendv_recvv(sockfd, iov, offset, bytes, false)
 #define qemu_sendv(sockfd, iov, offset, bytes) \
@@ -306,32 +308,29 @@ struct qemu_work_item {
 void qemu_init_vcpu(void *env);
 #endif
 
-/**
- * Sends an iovec (or optionally a part of it) down a socket, yielding
- * when the socket is full.
- */
-int qemu_co_sendv(int sockfd, struct iovec *iov,
-                  int len, int iov_offset);
 
 /**
- * Receives data into an iovec (or optionally into a part of it) from
- * a socket, yielding when there is no data in the socket.
+ * Sends a (part of) iovec down a socket, yielding when the socket is full, or
+ * Receives data into a (part of) iovec from a socket,
+ * yielding when there is no data in the socket.
+ * The same interface as qemu_sendv_recvv(), with added yielding.
+ * XXX should mark these as coroutine_fn
  */
-int qemu_co_recvv(int sockfd, struct iovec *iov,
-                  int len, int iov_offset);
-
+ssize_t qemu_co_sendv_recvv(int sockfd, struct iovec *iov,
+                            size_t offset, size_t bytes, bool do_sendv);
+#define qemu_co_recvv(sockfd, iov, offset, bytes) \
+  qemu_co_sendv_recvv(sockfd, iov, offset, bytes, false)
+#define qemu_co_sendv(sockfd, iov, offset, bytes) \
+  qemu_co_sendv_recvv(sockfd, iov, offset, bytes, true)
 
 /**
- * Sends a buffer down a socket, yielding when the socket is full.
+ * The same as above, but with just a single buffer
  */
-int qemu_co_send(int sockfd, void *buf, int len);
-
-/**
- * Receives data into a buffer from a socket, yielding when there
- * is no data in the socket.
- */
-int qemu_co_recv(int sockfd, void *buf, int len);
-
+ssize_t qemu_co_send_recv(int sockfd, void *buf, size_t bytes, bool do_sendv);
+#define qemu_co_recv(sockfd, buf, bytes) \
+  qemu_co_send_recv(sockfd, buf, bytes, false)
+#define qemu_co_send(sockfd, buf, bytes) \
+  qemu_co_send_recv(sockfd, buf, bytes, true)
 
 typedef struct QEMUIOVector {
     struct iovec *iov;
diff --git a/qemu-coroutine-io.c b/qemu-coroutine-io.c
index df8ff21..7c978ea 100644
--- a/qemu-coroutine-io.c
+++ b/qemu-coroutine-io.c
@@ -26,71 +26,39 @@
 #include "qemu_socket.h"
 #include "qemu-coroutine.h"
 
-int coroutine_fn qemu_co_recvv(int sockfd, struct iovec *iov,
-                               int len, int iov_offset)
+ssize_t coroutine_fn
+qemu_co_sendv_recvv(int sockfd, struct iovec *iov,
+                    size_t offset, size_t bytes, bool do_sendv)
 {
-    int total = 0;
-    int ret;
-    while (len) {
-        ret = qemu_recvv(sockfd, iov, iov_offset + total, len);
-        if (ret < 0) {
+    size_t done = 0;
+    ssize_t ret;
+    while (done < bytes) {
+        ret = qemu_sendv_recvv(sockfd, iov,
+                               offset + done, bytes - done, do_sendv);
+        if (ret > 0) {
+            done += ret;
+        } else if (ret < 0) {
             if (errno == EAGAIN) {
                 qemu_coroutine_yield();
-                continue;
-            }
-            if (total == 0) {
-                total = -1;
-            }
-            break;
-        }
-        if (ret == 0) {
-            break;
-        }
-        total += ret, len -= ret;
-    }
-
-    return total;
-}
-
-int coroutine_fn qemu_co_sendv(int sockfd, struct iovec *iov,
-                               int len, int iov_offset)
-{
-    int total = 0;
-    int ret;
-    while (len) {
-        ret = qemu_sendv(sockfd, iov, iov_offset + total, len);
-        if (ret < 0) {
-            if (errno == EAGAIN) {
-                qemu_coroutine_yield();
-                continue;
-            }
-            if (total == 0) {
-                total = -1;
+            } else if (done == 0) {
+                return -1;
+            } else {
+                break;
             }
+        } else if (ret == 0 && !do_sendv) {
+            /* write (send) should never return 0.
+             * read (recv) returns 0 for end-of-file (-data).
+             * In both cases there's little point retrying,
+             * but we do for write anyway, just in case */
             break;
         }
-        total += ret, len -= ret;
     }
-
-    return total;
+    return done;
 }
 
-int coroutine_fn qemu_co_recv(int sockfd, void *buf, int len)
+ssize_t coroutine_fn
+qemu_co_send_recv(int sockfd, void *buf, size_t bytes, bool do_sendv)
 {
-    struct iovec iov;
-
-    iov.iov_base = buf;
-    iov.iov_len = len;
-
-    return qemu_co_recvv(sockfd, &iov, len, 0);
-}
-
-int coroutine_fn qemu_co_send(int sockfd, void *buf, int len)
-{
-    struct iovec iov;
-
-    iov.iov_base = buf;
-    iov.iov_len = len;
-
-    return qemu_co_sendv(sockfd, &iov, len, 0);
+    struct iovec iov = { .iov_base = buf, .iov_len = bytes };
+    return qemu_co_sendv_recvv(sockfd, &iov, 0, bytes, do_sendv);
 }
