diff --git a/fsdev/9p-iov-marshal.c b/fsdev/9p-iov-marshal.c
index 4883b60d17..08d783ca11 100644
--- a/fsdev/9p-iov-marshal.c
+++ b/fsdev/9p-iov-marshal.c
@@ -76,15 +76,13 @@ ssize_t v9fs_pack(struct iovec *in_sg, int in_num, size_t offset,
     return v9fs_packunpack((void *)src, in_sg, in_num, offset, size, 1);
 }
 
-ssize_t v9fs_iov_unmarshal(struct iovec *out_sg, int out_num, size_t offset,
-                           int bswap, const char *fmt, ...)
+ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int out_num, size_t offset,
+                            int bswap, const char *fmt, va_list ap)
 {
     int i;
-    va_list ap;
     ssize_t copied = 0;
     size_t old_offset = offset;
 
-    va_start(ap, fmt);
     for (i = 0; fmt[i]; i++) {
         switch (fmt[i]) {
         case 'b': {
@@ -180,25 +178,34 @@ ssize_t v9fs_iov_unmarshal(struct iovec *out_sg, int out_num, size_t offset,
             break;
         }
         if (copied < 0) {
-            va_end(ap);
             return copied;
         }
         offset += copied;
     }
-    va_end(ap);
 
     return offset - old_offset;
 }
 
-ssize_t v9fs_iov_marshal(struct iovec *in_sg, int in_num, size_t offset,
-                         int bswap, const char *fmt, ...)
+ssize_t v9fs_iov_unmarshal(struct iovec *out_sg, int out_num, size_t offset,
+                           int bswap, const char *fmt, ...)
+{
+    ssize_t ret;
+    va_list ap;
+
+    va_start(ap, fmt);
+    ret = v9fs_iov_vunmarshal(out_sg, out_num, offset, bswap, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
+
+ssize_t v9fs_iov_vmarshal(struct iovec *in_sg, int in_num, size_t offset,
+                          int bswap, const char *fmt, va_list ap)
 {
     int i;
-    va_list ap;
     ssize_t copied = 0;
     size_t old_offset = offset;
 
-    va_start(ap, fmt);
     for (i = 0; fmt[i]; i++) {
         switch (fmt[i]) {
         case 'b': {
@@ -290,12 +297,23 @@ ssize_t v9fs_iov_marshal(struct iovec *in_sg, int in_num, size_t offset,
             break;
         }
         if (copied < 0) {
-            va_end(ap);
             return copied;
         }
         offset += copied;
     }
-    va_end(ap);
 
     return offset - old_offset;
 }
+
+ssize_t v9fs_iov_marshal(struct iovec *in_sg, int in_num, size_t offset,
+                         int bswap, const char *fmt, ...)
+{
+    ssize_t ret;
+    va_list ap;
+
+    va_start(ap, fmt);
+    ret = v9fs_iov_vmarshal(in_sg, in_num, offset, bswap, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
diff --git a/fsdev/9p-iov-marshal.h b/fsdev/9p-iov-marshal.h
index 993614f544..6bccbfb41a 100644
--- a/fsdev/9p-iov-marshal.h
+++ b/fsdev/9p-iov-marshal.h
@@ -10,4 +10,9 @@ ssize_t v9fs_iov_unmarshal(struct iovec *out_sg, int out_num, size_t offset,
                            int bswap, const char *fmt, ...);
 ssize_t v9fs_iov_marshal(struct iovec *in_sg, int in_num, size_t offset,
                          int bswap, const char *fmt, ...);
+
+ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int out_num, size_t offset,
+                            int bswap, const char *fmt, va_list ap);
+ssize_t v9fs_iov_vmarshal(struct iovec *in_sg, int in_num, size_t offset,
+                          int bswap, const char *fmt, va_list ap);
 #endif
diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index d8ce12ed88..a740f85625 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -39,6 +39,32 @@ enum {
     Oappend = 0x80,
 };
 
+ssize_t pdu_marshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
+{
+    ssize_t ret;
+    va_list ap;
+
+    va_start(ap, fmt);
+    ret = v9fs_iov_vmarshal(pdu->elem.in_sg, pdu->elem.in_num,
+                            offset, 1, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
+
+ssize_t pdu_unmarshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
+{
+    ssize_t ret;
+    va_list ap;
+
+    va_start(ap, fmt);
+    ret = v9fs_iov_vunmarshal(pdu->elem.out_sg, pdu->elem.out_num,
+                              offset, 1, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
+
 static int omode_to_uflags(int8_t mode)
 {
     int ret = 0;
diff --git a/hw/9pfs/virtio-9p.h b/hw/9pfs/virtio-9p.h
index 3a7e136ab6..d6f3ac08a7 100644
--- a/hw/9pfs/virtio-9p.h
+++ b/hw/9pfs/virtio-9p.h
@@ -320,10 +320,8 @@ extern void v9fs_path_copy(V9fsPath *lhs, V9fsPath *rhs);
 extern int v9fs_name_to_path(V9fsState *s, V9fsPath *dirpath,
                              const char *name, V9fsPath *path);
 
-#define pdu_marshal(pdu, offset, fmt, args...)  \
-    v9fs_iov_marshal(pdu->elem.in_sg, pdu->elem.in_num, offset, 1, fmt, ##args)
-#define pdu_unmarshal(pdu, offset, fmt, args...)  \
-    v9fs_iov_unmarshal(pdu->elem.out_sg, pdu->elem.out_num, offset, 1, fmt, ##args)
+ssize_t pdu_marshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...);
+ssize_t pdu_unmarshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...);
 
 #define TYPE_VIRTIO_9P "virtio-9p-device"
 #define VIRTIO_9P(obj) \