Index: head/sys/dev/hyperv/vmbus/hv_channel.c
===================================================================
--- head/sys/dev/hyperv/vmbus/hv_channel.c
+++ head/sys/dev/hyperv/vmbus/hv_channel.c
@@ -633,12 +633,12 @@
 
 	hlen = sizeof(pkt);
 	pktlen = hlen + dlen;
-	pad_pktlen = roundup2(pktlen, VMBUS_CHANPKT_SIZE_ALIGN);
+	pad_pktlen = VMBUS_CHANPKT_TOTLEN(pktlen);
 
 	pkt.cp_hdr.cph_type = type;
 	pkt.cp_hdr.cph_flags = flags;
-	pkt.cp_hdr.cph_hlen = hlen >> VMBUS_CHANPKT_SIZE_SHIFT;
-	pkt.cp_hdr.cph_tlen = pad_pktlen >> VMBUS_CHANPKT_SIZE_SHIFT;
+	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_hlen, hlen);
+	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_tlen, pad_pktlen);
 	pkt.cp_hdr.cph_xactid = xactid;
 
 	iov[0].iov_base = &pkt;
@@ -669,12 +669,12 @@
 
 	hlen = __offsetof(struct vmbus_chanpkt_sglist, cp_gpa[sglen]);
 	pktlen = hlen + dlen;
-	pad_pktlen = roundup2(pktlen, VMBUS_CHANPKT_SIZE_ALIGN);
+	pad_pktlen = VMBUS_CHANPKT_TOTLEN(pktlen);
 
 	pkt.cp_hdr.cph_type = VMBUS_CHANPKT_TYPE_GPA;
 	pkt.cp_hdr.cph_flags = VMBUS_CHANPKT_FLAG_RC;
-	pkt.cp_hdr.cph_hlen = hlen >> VMBUS_CHANPKT_SIZE_SHIFT;
-	pkt.cp_hdr.cph_tlen = pad_pktlen >> VMBUS_CHANPKT_SIZE_SHIFT;
+	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_hlen, hlen);
+	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_tlen, pad_pktlen);
 	pkt.cp_hdr.cph_xactid = xactid;
 	pkt.cp_rsvd = 0;
 	pkt.cp_gpa_cnt = sglen;
@@ -711,12 +711,12 @@
 	hlen = __offsetof(struct vmbus_chanpkt_prplist,
 	    cp_range[0].gpa_page[prp_cnt]);
 	pktlen = hlen + dlen;
-	pad_pktlen = roundup2(pktlen, VMBUS_CHANPKT_SIZE_ALIGN);
+	pad_pktlen = VMBUS_CHANPKT_TOTLEN(pktlen);
 
 	pkt.cp_hdr.cph_type = VMBUS_CHANPKT_TYPE_GPA;
 	pkt.cp_hdr.cph_flags = VMBUS_CHANPKT_FLAG_RC;
-	pkt.cp_hdr.cph_hlen = hlen >> VMBUS_CHANPKT_SIZE_SHIFT;
-	pkt.cp_hdr.cph_tlen = pad_pktlen >> VMBUS_CHANPKT_SIZE_SHIFT;
+	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_hlen, hlen);
+	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_tlen, pad_pktlen);
 	pkt.cp_hdr.cph_xactid = xactid;
 	pkt.cp_rsvd = 0;
 	pkt.cp_range_cnt = 1;
Index: head/sys/dev/hyperv/vmbus/vmbus_reg.h
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_reg.h
+++ head/sys/dev/hyperv/vmbus/vmbus_reg.h
@@ -115,6 +115,14 @@
 #define VMBUS_CHANPKT_SIZE_SHIFT	3
 #define VMBUS_CHANPKT_SIZE_ALIGN	(1 << VMBUS_CHANPKT_SIZE_SHIFT)
 
+#define VMBUS_CHANPKT_SETLEN(pktlen, len)		\
+do {							\
+	(pktlen) = (len) >> VMBUS_CHANPKT_SIZE_SHIFT;	\
+} while (0)
+
+#define VMBUS_CHANPKT_TOTLEN(tlen)	\
+	roundup2((tlen), VMBUS_CHANPKT_SIZE_ALIGN)
+
 struct vmbus_chanpkt_hdr {
 	uint16_t	cph_type;
 	uint16_t	cph_hlen;	/* header len, in 8 bytes */