Index: sys/dev/mps/mps.c
===================================================================
--- sys/dev/mps/mps.c
+++ sys/dev/mps/mps.c
@@ -1350,6 +1350,7 @@
 	sc->disable_msix = 0;
 	sc->disable_msi = 0;
 	sc->max_chains = MPS_CHAIN_FRAMES;
+	sc->max_io_pages = MPS_MAXIO_PAGES;
 	sc->enable_ssu = MPS_SSU_ENABLE_SSD_DISABLE_HDD;
 	sc->spinup_wait_time = DEFAULT_SPINUP_WAIT;
 
@@ -1360,6 +1361,7 @@
 	TUNABLE_INT_FETCH("hw.mps.disable_msix", &sc->disable_msix);
 	TUNABLE_INT_FETCH("hw.mps.disable_msi", &sc->disable_msi);
 	TUNABLE_INT_FETCH("hw.mps.max_chains", &sc->max_chains);
+	TUNABLE_INT_FETCH("hw.mps.max_io_pages", &sc->max_io_pages);
 	TUNABLE_INT_FETCH("hw.mps.enable_ssu", &sc->enable_ssu);
 	TUNABLE_INT_FETCH("hw.mps.spinup_wait_time", &sc->spinup_wait_time);
 
@@ -1380,6 +1382,10 @@
 	    device_get_unit(sc->mps_dev));
 	TUNABLE_INT_FETCH(tmpstr, &sc->max_chains);
 
+	snprintf(tmpstr, sizeof(tmpstr), "dev.mps.%d.max_io_pages",
+	    device_get_unit(sc->mps_dev));
+	TUNABLE_INT_FETCH(tmpstr, &sc->max_io_pages);
+
 	bzero(sc->exclude_ids, sizeof(sc->exclude_ids));
 	snprintf(tmpstr, sizeof(tmpstr), "dev.mps.%d.exclude_ids",
 	    device_get_unit(sc->mps_dev));
@@ -1465,6 +1471,11 @@
 	    &sc->max_chains, 0,"maximum chain frames that will be allocated");
 
 	SYSCTL_ADD_INT(sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
+	    OID_AUTO, "max_io_pages", CTLFLAG_RD,
+	    &sc->max_io_pages, 0,"maximum pages to allow per I/O (if <1 use "
+	    "IOCFacts)");
+
+	SYSCTL_ADD_INT(sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
 	    OID_AUTO, "enable_ssu", CTLFLAG_RW, &sc->enable_ssu, 0,
 	    "enable SSU to SATA SSD/HDD at shutdown");
 
Index: sys/dev/mps/mps_sas.c
===================================================================
--- sys/dev/mps/mps_sas.c
+++ sys/dev/mps/mps_sas.c
@@ -928,6 +928,8 @@
 	case XPT_PATH_INQ:
 	{
 		struct ccb_pathinq *cpi = &ccb->cpi;
+		struct mps_softc *sc = sassc->sc;
+		uint8_t sges_per_frame;
 
 		cpi->version_num = 1;
 		cpi->hba_inquiry = PI_SDTR_ABLE|PI_TAG_ABLE|PI_WIDE_16;
@@ -951,12 +953,23 @@
 		cpi->transport_version = 0;
 		cpi->protocol = PROTO_SCSI;
 		cpi->protocol_version = SCSI_REV_SPC;
-#if __FreeBSD_version >= 800001
+
 		/*
-		 * XXX KDM where does this number come from?
-		 */
-		cpi->maxio = 256 * 1024;
-#endif
+		 * Max IO Size is Page Size * the following:
+		 * ((SGEs per frame - 1 for chain element) *
+		 * Max Chain Depth) + 1 for no chain needed in last frame
+		 *
+		 * If user suggests a Max IO size to use, use the smaller of the
+		 * user's value and the calculated value as long as the user's
+		 * value is larger than 0. The user's value is in pages.
+		 */
+		sges_per_frame = ((sc->facts->IOCRequestFrameSize * 4) /
+		    sizeof(MPI2_SGE_SIMPLE64)) - 1;
+		cpi->maxio = (sges_per_frame * sc->facts->MaxChainDepth) + 1;
+		cpi->maxio *= PAGE_SIZE;
+		if ((sc->max_io_pages > 0) && (sc->max_io_pages * PAGE_SIZE <
+		    cpi->maxio))
+			cpi->maxio = sc->max_io_pages * PAGE_SIZE;
 		mpssas_set_ccbstatus(ccb, CAM_REQ_CMP);
 		break;
 	}
Index: sys/dev/mps/mpsvar.h
===================================================================
--- sys/dev/mps/mpsvar.h
+++ sys/dev/mps/mpsvar.h
@@ -41,6 +41,7 @@
 #define MPS_EVT_REPLY_FRAMES	32
 #define MPS_REPLY_FRAMES	MPS_REQ_FRAMES
 #define MPS_CHAIN_FRAMES	2048
+#define MPS_MAXIO_PAGES		(-1)
 #define MPS_SENSE_LEN		SSD_FULL_SIZE
 #define MPS_MSI_COUNT		1
 #define MPS_SGE64_SIZE		12
@@ -280,6 +281,7 @@
 	int				io_cmds_highwater;
 	int				chain_free;
 	int				max_chains;
+	int				max_io_pages;
 	int				chain_free_lowwater;
 	u_int				enable_ssu;
 	int				spinup_wait_time;