Index: head/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c
===================================================================
--- head/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c
+++ head/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c
@@ -88,10 +88,25 @@
 
 #define VSTOR_PKT_SIZE	(sizeof(struct vstor_packet) - vmscsi_size_delta)
 
-#define STORVSC_DATA_SEGCNT_MAX		32
+/*
+ * 33 segments are needed to allow 128KB maxio, in case the data
+ * in the first page is _not_ PAGE_SIZE aligned, e.g.
+ *
+ *     |<----------- 128KB ----------->|
+ *     |                               |
+ *  0  2K 4K    8K   16K   124K  128K  130K
+ *  |  |  |     |     |       |     |  |
+ *  +--+--+-----+-----+.......+-----+--+--+
+ *  |  |  |     |     |       |     |  |  | DATA
+ *  |  |  |     |     |       |     |  |  |
+ *  +--+--+-----+-----+.......------+--+--+
+ *     |  |                         |  |
+ *     | 1|            31           | 1| ...... # of segments
+ */
+#define STORVSC_DATA_SEGCNT_MAX		33
 #define STORVSC_DATA_SEGSZ_MAX		PAGE_SIZE
 #define STORVSC_DATA_SIZE_MAX		\
-	(STORVSC_DATA_SEGCNT_MAX * STORVSC_DATA_SEGSZ_MAX)
+	((STORVSC_DATA_SEGCNT_MAX - 1) * STORVSC_DATA_SEGSZ_MAX)
 
 struct storvsc_softc;
 
@@ -1386,6 +1401,7 @@
 		cpi->hba_misc = PIM_NOBUSRESET;
 		if (hv_storvsc_use_pim_unmapped)
 			cpi->hba_misc |= PIM_UNMAPPED;
+		cpi->maxio = STORVSC_DATA_SIZE_MAX;
 		cpi->hba_eng_cnt = 0;
 		cpi->max_target = STORVSC_MAX_TARGETS;
 		cpi->max_lun = sc->hs_drv_props->drv_max_luns_per_target;