diff --git a/devicemodel/hw/pci/core.c b/devicemodel/hw/pci/core.c
index 2e21d28e2..66b0c0b0a 100644
--- a/devicemodel/hw/pci/core.c
+++ b/devicemodel/hw/pci/core.c
@@ -1371,7 +1371,7 @@ init_pci(struct vmctx *ctx)
 	struct slotinfo *si;
 	struct funcinfo *fi;
 	int bus, slot, func, i;
-	int success_cnt = 0;
+	int success_cnt[2] = {0};	/* 0 for passthru and 1 for others */
 	int error;
 	uint64_t bus0_memlimit;
 
@@ -1393,25 +1393,40 @@ init_pci(struct vmctx *ctx)
 		bi->membase32 = pci_emul_membase32;
 		bi->membase64 = pci_emul_membase64;
 
-		for (slot = 0; slot < MAXSLOTS; slot++) {
-			si = &bi->slotinfo[slot];
-			for (func = 0; func < MAXFUNCS; func++) {
-				fi = &si->si_funcs[func];
-				if (fi->fi_name == NULL)
-					continue;
-				ops = pci_emul_finddev(fi->fi_name);
-				if (!ops) {
-					pr_warn("No driver for device [%s]\n", fi->fi_name);
-					continue;
+		/*
+		 * Initialize pass-thru devices firstly to reserve PIO bar regions.
+		 * For pass-thru devices, ACRN-DM need to ensure PIO bar regions identical mapping
+		 * (guest PIO bar start address equals to host PIO bar start address).
+		 *
+		 * Then initialize non pass-thru devices.
+		 */
+		for (i = 0; i < 2; i++) {
+			for (slot = 0; slot < MAXSLOTS; slot++) {
+				si = &bi->slotinfo[slot];
+				for (func = 0; func < MAXFUNCS; func++) {
+					fi = &si->si_funcs[func];
+					if (fi->fi_name == NULL)
+						continue;
+					ops = pci_emul_finddev(fi->fi_name);
+					if (!ops) {
+						pr_warn("No driver for device [%s]\n", fi->fi_name);
+						continue;
+					}
+
+					if ((i == 0) && strcmp(ops->class_name, "passthru")) {
+						continue;
+					} else if ((i == 1) && !strcmp(ops->class_name, "passthru")) {
+						continue;
+					}
+
+					pr_notice("pci init %s\r\n", fi->fi_name);
+					error = pci_emul_init(ctx, ops, bus, slot, func, fi);
+					if (error) {
+						pr_err("pci %s init failed\n", fi->fi_name);
+						goto pci_emul_init_fail;
+					}
+					success_cnt[i]++;
 				}
-				pr_notice("pci init %s\r\n", fi->fi_name);
-				error = pci_emul_init(ctx, ops, bus, slot,
-				    func, fi);
-				if (error) {
-					pr_err("pci %s init failed\n", fi->fi_name);
-					goto pci_emul_init_fail;
-				}
-				success_cnt++;
 			}
 		}
 
@@ -1452,6 +1467,19 @@ init_pci(struct vmctx *ctx)
 	}
 	bi->memlimit32 = bus0_memlimit;
 
+	/* Update the PIO window in the guest ACPI DSDT table */
+	for (i = 0; i < REGION_NUMS; i++) {
+		if (reserved_bar_regions[i].vdev &&
+				reserved_bar_regions[i].bar_type == PCIBAR_IO) {
+			if (reserved_bar_regions[i].start < bi->iobase) {
+				bi->iobase = reserved_bar_regions[i].start;
+			}
+			if ((reserved_bar_regions[i].end + 1) > bi->iolimit) {
+				bi->iolimit = reserved_bar_regions[i].end + 1;
+			}	
+		}
+	}
+
 	error = check_gsi_sharing_violation();
 	if (error < 0)
 		goto pci_emul_init_fail;
@@ -1532,25 +1560,34 @@ init_pci(struct vmctx *ctx)
 	return 0;
 
 pci_emul_init_fail:
-	for (bus = 0; bus < MAXBUSES && success_cnt > 0; bus++) {
-		bi = pci_businfo[bus];
-		if (bi == NULL)
-			continue;
-		for (slot = 0; slot < MAXSLOTS && success_cnt > 0; slot++) {
-			si = &bi->slotinfo[slot];
-			for (func = 0; func < MAXFUNCS; func++) {
-				fi = &si->si_funcs[func];
-				if (fi->fi_name == NULL)
-					continue;
-				if (success_cnt-- <= 0)
-					break;
-				ops = pci_emul_finddev(fi->fi_name);
-				if (!ops) {
-					pr_warn("No driver for device [%s]\n", fi->fi_name);
-					continue;
+	for (i = 0; i < 2; i++) {
+		for (bus = 0; bus < MAXBUSES && success_cnt[i] > 0; bus++) {
+			bi = pci_businfo[bus];
+			if (bi == NULL)
+				continue;
+			for (slot = 0; slot < MAXSLOTS && success_cnt[i] > 0; slot++) {
+				si = &bi->slotinfo[slot];
+				for (func = 0; func < MAXFUNCS; func++) {
+					fi = &si->si_funcs[func];
+					if (fi->fi_name == NULL)
+						continue;
+					if (success_cnt[i]-- <= 0)
+						break;
+					ops = pci_emul_finddev(fi->fi_name);
+					if (!ops) {
+						pr_warn("No driver for device [%s]\n", fi->fi_name);
+						continue;
+					}
+
+					if ((i == 0) && strcmp(ops->class_name, "passthru")) {
+						continue;
+					} else if ((i == 1) && !strcmp(ops->class_name, "passthru")) {
+						continue;
+					}
+
+					pci_emul_deinit(ctx, ops, bus, slot,
+						func, fi);
 				}
-				pci_emul_deinit(ctx, ops, bus, slot,
-				    func, fi);
 			}
 		}
 	}
diff --git a/devicemodel/hw/pci/passthrough.c b/devicemodel/hw/pci/passthrough.c
index 00584a93c..39e6aa8ad 100644
--- a/devicemodel/hw/pci/passthrough.c
+++ b/devicemodel/hw/pci/passthrough.c
@@ -243,7 +243,12 @@ cfginitbar(struct vmctx *ctx, struct passthru_dev *ptdev)
 		if (size == 0)
 			continue;
 
-		/* Allocate the BAR in the guest I/O or MMIO space */
+		if (bartype == PCIBAR_IO)
+			error = reserve_io_rgn(base, base + size - 1, i, PCIBAR_IO, dev);
+		if (error)
+			return -1;
+
+		/* Allocate the BAR in the guest MMIO space */
 		error = pci_emul_alloc_pbar(dev, i, base, bartype, size);
 		if (error)
 			return -1;
@@ -750,6 +755,8 @@ passthru_deinit(struct vmctx *ctx, struct pci_vdev *dev, char *opts)
 		return;
 	}
 
+	destory_io_rsvd_rgns(dev);
+
 	ptdev = (struct passthru_dev *) dev->arg;
 
 	pr_info("vm_reset_ptdev_intx:0x%x-%x, ioapic virpin=%d.\n",
diff --git a/devicemodel/include/pci_core.h b/devicemodel/include/pci_core.h
index 62cf4382c..f1fba5c59 100644
--- a/devicemodel/include/pci_core.h
+++ b/devicemodel/include/pci_core.h
@@ -51,10 +51,8 @@
 #define SOFTWARE_SRAM_MAX_SIZE	0x00800000UL
 #define SOFTWARE_SRAM_BASE_GPA	(PCI_EMUL_MEMBASE32 - SOFTWARE_SRAM_MAX_SIZE)
 
-/* Currently,only gvt need reserved bar regions,
- * so just hardcode REGION_NUMS=5 here
- */
-#define REGION_NUMS 5
+/* GVT BARs + PTDEV IO BARs */
+#define REGION_NUMS 32
 
 struct vmctx;
 struct pci_vdev;