Index: head/sys/dev/hyperv/include/vmbus_xact.h
===================================================================
--- head/sys/dev/hyperv/include/vmbus_xact.h
+++ head/sys/dev/hyperv/include/vmbus_xact.h
@@ -51,6 +51,8 @@
 void			vmbus_xact_deactivate(struct vmbus_xact *xact);
 const void		*vmbus_xact_wait(struct vmbus_xact *xact,
 			    size_t *resp_len);
+const void		*vmbus_xact_busywait(struct vmbus_xact *xact,
+			    size_t *resp_len);
 void			vmbus_xact_wakeup(struct vmbus_xact *xact,
 			    const void *data, size_t dlen);
 void			vmbus_xact_ctx_wakeup(struct vmbus_xact_ctx *ctx,
Index: head/sys/dev/hyperv/vmbus/vmbus_xact.c
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_xact.c
+++ head/sys/dev/hyperv/vmbus/vmbus_xact.c
@@ -69,6 +69,8 @@
 static void			vmbus_xact_free(struct vmbus_xact *);
 static struct vmbus_xact	*vmbus_xact_get1(struct vmbus_xact_ctx *,
 				    uint32_t);
+const void			*vmbus_xact_wait1(struct vmbus_xact *, size_t *,
+				    bool);
 
 static struct vmbus_xact *
 vmbus_xact_alloc(struct vmbus_xact_ctx *ctx, bus_dma_tag_t parent_dtag)
@@ -249,7 +251,8 @@
 }
 
 const void *
-vmbus_xact_wait(struct vmbus_xact *xact, size_t *resp_len)
+vmbus_xact_wait1(struct vmbus_xact *xact, size_t *resp_len,
+    bool can_sleep)
 {
 	struct vmbus_xact_ctx *ctx = xact->x_ctx;
 	const void *resp;
@@ -258,8 +261,14 @@
 
 	KASSERT(ctx->xc_active == xact, ("xact mismatch"));
 	while (xact->x_resp == NULL) {
-		mtx_sleep(&ctx->xc_active, &ctx->xc_active_lock, 0,
-		    "wxact", 0);
+		if (can_sleep) {
+			mtx_sleep(&ctx->xc_active, &ctx->xc_active_lock, 0,
+			    "wxact", 0);
+		} else {
+			mtx_unlock(&ctx->xc_active_lock);
+			DELAY(1000);
+			mtx_lock(&ctx->xc_active_lock);
+		}
 	}
 	ctx->xc_active = NULL;
 
@@ -271,6 +280,20 @@
 	return (resp);
 }
 
+const void *
+vmbus_xact_wait(struct vmbus_xact *xact, size_t *resp_len)
+{
+
+	return (vmbus_xact_wait1(xact, resp_len, true /* can sleep */));
+}
+
+const void *
+vmbus_xact_busywait(struct vmbus_xact *xact, size_t *resp_len)
+{
+
+	return (vmbus_xact_wait1(xact, resp_len, false /* can't sleep */));
+}
+
 static void
 vmbus_xact_save_resp(struct vmbus_xact *xact, const void *data, size_t dlen)
 {