diff --git a/hypervisor/Makefile b/hypervisor/Makefile
index 068e20c22..dcf837943 100644
--- a/hypervisor/Makefile
+++ b/hypervisor/Makefile
@@ -301,6 +301,7 @@ VP_DM_C_SRCS += dm/vpci/vpci_bridge.c
 VP_DM_C_SRCS += dm/vpci/pci_pt.c
 VP_DM_C_SRCS += dm/vpci/vmsi.c
 VP_DM_C_SRCS += dm/vpci/vmsix.c
+VP_DM_C_SRCS += dm/vpci/vmsix_on_msi.c
 VP_DM_C_SRCS += dm/vpci/vsriov.c
 VP_DM_C_SRCS += arch/x86/guest/vlapic.c
 VP_DM_C_SRCS += arch/x86/guest/pm.c
diff --git a/hypervisor/dm/vpci/pci_pt.c b/hypervisor/dm/vpci/pci_pt.c
index 429e2e21d..541a7060f 100644
--- a/hypervisor/dm/vpci/pci_pt.c
+++ b/hypervisor/dm/vpci/pci_pt.c
@@ -374,6 +374,7 @@ void init_vdev_pt(struct pci_vdev *vdev, bool is_pf_vdev)
 	/* Initialize the vdev BARs except SRIOV VF, VF BARs are initialized directly from create_vf function */
 	if (vdev->phyfun == NULL) {
 		init_bars(vdev, is_pf_vdev);
+		init_vmsix_on_msi(vdev);
 		if (is_prelaunched_vm(vpci2vm(vdev->vpci)) && (!is_pf_vdev)) {
 			pci_command = (uint16_t)pci_pdev_read_cfg(vdev->pdev->bdf, PCIR_COMMAND, 2U);
 
diff --git a/hypervisor/dm/vpci/vmsix.c b/hypervisor/dm/vpci/vmsix.c
index 588c56328..a90fb84e6 100644
--- a/hypervisor/dm/vpci/vmsix.c
+++ b/hypervisor/dm/vpci/vmsix.c
@@ -174,7 +174,11 @@ static void rw_vmsix_table(struct pci_vdev *vdev, struct mmio_request *mmio, uin
 				/* Write to pci_vdev */
 				(void)memcpy_s((void *)entry + entry_offset, (size_t)mmio->size,
 						&mmio->value, (size_t)mmio->size);
-				remap_one_vmsix_entry(vdev, index);
+				if (vdev->msix.is_vmsix_on_msi) {
+					remap_one_vmsix_entry_on_msi(vdev, index);
+				} else {
+					remap_one_vmsix_entry(vdev, index);
+				}
 			} else {
 				pr_err("%s, Only DWORD and QWORD are permitted", __func__);
 			}
@@ -205,6 +209,15 @@ int32_t vmsix_handle_table_mmio_access(struct io_request *io_req, void *handler_
 
 		if (msixtable_access(vdev, (uint32_t)offset)) {
 			rw_vmsix_table(vdev, mmio, (uint32_t)offset);
+		} else if (vdev->msix.is_vmsix_on_msi) {
+			/* According to PCI spec, PBA is read-only.
+			 * Don't emulate PBA according to the device status, just return 0.
+			 */
+			if (mmio->direction == REQUEST_READ) {
+				mmio->value = 0UL;
+			} else {
+				ret = -EINVAL;
+			}
 		} else {
 			hva = hpa2hva(vdev->msix.mmio_hpa + offset);
 
diff --git a/hypervisor/dm/vpci/vmsix_on_msi.c b/hypervisor/dm/vpci/vmsix_on_msi.c
new file mode 100644
index 000000000..5fa14a813
--- /dev/null
+++ b/hypervisor/dm/vpci/vmsix_on_msi.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright (C) 2020 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <vm.h>
+#include <ptdev.h>
+#include <assign.h>
+#include <vpci.h>
+#include <vtd.h>
+#include <board.h>
+#include "vpci_priv.h"
+
+#define PER_VECTOR_MASK_CAP 0x0100U
+
+/* Pre-assumptions for vMSI-x on MSI emulation:
+ * 1. The device is in vmsix_on_msi_devs array.
+ * 2. The device should support MSI capability as well as per-vector mask
+ * 3. The device doesn't support MSI-x capability.
+ * 4. The device should have an unused BAR (this condition is checked inside init_vmsix_on_msi).
+ * 5. HV doesn't emulate PBA according to physcial device status, the device driver should not rely on PBA
+ *    for functionality.
+ */
+static bool need_vmsix_on_msi_emulation(__unused struct pci_pdev *pdev, __unused uint16_t *vector_count)
+{
+	bool ret = false;
+#if (MAX_VMSIX_ON_MSI_PDEVS_NUM > 0)
+	uint16_t msgctrl;
+	uint32_t i;
+
+	for(i = 0U; i < MAX_VMSIX_ON_MSI_PDEVS_NUM; i++) {
+		if (pdev->bdf.value == vmsix_on_msi_devs[i].bdf.value) {
+			if ((pdev->msi_capoff != 0U) && (pdev->msix.capoff == 0U)) {
+				msgctrl = (uint16_t)pci_pdev_read_cfg(pdev->bdf, pdev->msi_capoff + PCIR_MSI_CTRL, 2U);
+				*vector_count = 1U << ((msgctrl & PCIM_MSICTRL_MMC_MASK) >> 1U);
+				if ((*vector_count > 1U) && ((msgctrl & PER_VECTOR_MASK_CAP) != 0U)) {
+					ret = true;
+				}
+			}
+			break;
+		}
+	}
+#endif
+
+	return ret;
+}
+
+void reserve_vmsix_on_msi_irtes(struct pci_pdev *pdev)
+{
+	struct intr_source intr_src;
+	uint16_t count = 0;
+	int32_t ret;
+
+	if (need_vmsix_on_msi_emulation(pdev, &count)) {
+		intr_src.is_msi = true;
+		intr_src.src.msi.value = pdev->bdf.value;
+		ret = dmar_reserve_irte(&intr_src, count, &pdev->irte_start);
+		if ((ret == 0) && (pdev->irte_start != INVALID_IRTE_ID)) {
+			pdev->irte_count = count;
+		}
+	}
+}
+
+static inline uint32_t get_mask_bits_offset(const struct pci_vdev *vdev)
+{
+	return vdev->msi.is_64bit ? (vdev->msix.capoff + 0x10U) : (vdev->msix.capoff + 0xCU);
+}
+
+/**
+ * @pre vdev != NULL
+ * @pre vdev->pdev != NULL
+ */
+void init_vmsix_on_msi(struct pci_vdev *vdev)
+{
+	struct pci_pdev *pdev = vdev->pdev;
+	uint32_t i;
+
+	/* irte_count > 1 only when the device needs vMSI-x on MSI emulation and IRTEs are reserved successfully */
+	if (pdev->irte_count > 1U) {
+		/* find an unused BAR */
+		for (i = 0U; i < vdev->nr_bars; i++) {
+			if (vdev->vbars[i].base_hpa == 0UL){
+				break;
+			}
+			if (vdev->vbars[i].type == PCIBAR_MEM64) {
+				i++;
+			}
+		}
+		if (i < vdev->nr_bars) {
+			vdev->msix.capoff = pdev->msi_capoff;
+			vdev->msi.capoff = 0U;
+			vdev->msix.is_vmsix_on_msi = true;
+			/* For a device support MSI with per-vector mask, the length of MSI cap is at least 20 bytes */
+			vdev->msix.caplen = MSIX_CAPLEN;
+			vdev->msix.table_bar = i;
+			vdev->msix.table_offset = 0U;
+			vdev->msix.table_count = pdev->irte_count;
+
+			/* capability ID */
+			pci_vdev_write_vcfg(vdev, vdev->msix.capoff, 1U, 0x11U);
+			/* message control, MSI-X Diabled, Function unamsked */
+			pci_vdev_write_vcfg(vdev, vdev->msix.capoff + 2U, 2U, pdev->irte_count - 1U);
+			/* Init MSIX table vBAR, offset is 0 */
+			pci_vdev_write_vcfg(vdev, vdev->msix.capoff + 4U, 4U, i);
+			/* Init PBA table vBAR, offset is 2048 */
+			pci_vdev_write_vcfg(vdev, vdev->msix.capoff + 8U, 4U, 2048U + i);
+
+			vdev->vbars[i].type = PCIBAR_MEM32;
+			vdev->vbars[i].size = 4096U;
+			vdev->vbars[i].base_hpa = 0x0UL;
+			vdev->vbars[i].mask = 0xFFFFF000U & PCI_BASE_ADDRESS_MEM_MASK;
+			/* fixed for memory, 32bit, non-prefetchable */
+			vdev->vbars[i].fixed = 0U;
+
+			/* About MSI-x bar GPA:
+			 * - For Service VM: when first time init, it is programmed as 0, then OS will program
+			 * the value later and the value is stored in  vdev->vbars[MSI-X_BAR_ID].base_gpa.
+			 * When the device is assigned to UOS and then assgined back to SOS, the stored base
+			 * GPA will be used.
+			 * - For Post-launched VM: The GPA is assigned by device model.
+			 * - For Pre-launched VM: Not supported yet.
+			 */
+			vdev->msix.mmio_gpa = vdev->vbars[i].base_gpa;
+			vdev_pt_write_vbar(vdev, i, (uint32_t)(vdev->vbars[i].base_gpa & 0xFFFFFFFFUL));
+		}
+	}
+}
+
+void write_vmsix_cap_reg_on_msi(struct pci_vdev *vdev, uint32_t offset, uint32_t bytes, uint32_t val)
+{
+	uint16_t old_msgctrl, msgctrl;
+	uint16_t msi_msgctrl;
+
+	old_msgctrl = (uint16_t)pci_vdev_read_vcfg(vdev, vdev->msix.capoff + PCIR_MSIX_CTRL, 2U);
+	/* Write to vdev */
+	pci_vdev_write_vcfg(vdev, offset, bytes, val);
+	msgctrl = (uint16_t)pci_vdev_read_vcfg(vdev, vdev->msix.capoff + PCIR_MSIX_CTRL, 2U);
+
+	if (((old_msgctrl ^ msgctrl) & (PCIM_MSIXCTRL_MSIX_ENABLE | PCIM_MSIXCTRL_FUNCTION_MASK)) != 0U) {
+		msi_msgctrl = (uint16_t)pci_pdev_read_cfg(vdev->pdev->bdf, offset, 2U);
+
+		msi_msgctrl = msi_msgctrl & (~PCIM_MSICTRL_MME_MASK);
+		msi_msgctrl &= ~ PCIM_MSICTRL_MSI_ENABLE;
+
+		/* If MSI Enable is being set, make sure INTxDIS bit is set */
+		if ((msgctrl & PCIM_MSIXCTRL_MSIX_ENABLE) != 0U) {
+			enable_disable_pci_intx(vdev->pdev->bdf, false);
+			msi_msgctrl |= (msi_msgctrl & PCIM_MSICTRL_MMC_MASK) << 3U;
+			msi_msgctrl |= PCIM_MSICTRL_MSI_ENABLE;
+		}
+		pci_pdev_write_cfg(vdev->pdev->bdf, offset, 2U, msi_msgctrl);
+
+		if ((msgctrl & PCIM_MSIXCTRL_FUNCTION_MASK) != 0U) {
+			pci_pdev_write_cfg(vdev->pdev->bdf, get_mask_bits_offset(vdev), 4U, 0xFFFFFFFFU);
+		}
+	}
+}
+
+void remap_one_vmsix_entry_on_msi(struct pci_vdev *vdev, uint32_t index)
+{
+	const struct msix_table_entry *ventry;
+	uint32_t mask_bits;
+	uint32_t vector_mask = 1U << index;
+	struct msi_info info = {};
+	union pci_bdf pbdf = vdev->pdev->bdf;
+	union irte_index ir_index;
+	int32_t ret = 0;
+	uint32_t capoff = vdev->msix.capoff;
+
+	mask_bits = pci_pdev_read_cfg(pbdf, get_mask_bits_offset(vdev), 4U);
+	mask_bits |= vector_mask;
+	pci_pdev_write_cfg(pbdf, get_mask_bits_offset(vdev), 4U, mask_bits);
+
+	ventry = &vdev->msix.table_entries[index];
+	if ((ventry->vector_control & PCIM_MSIX_VCTRL_MASK) == 0U) {
+		info.addr.full = vdev->msix.table_entries[index].addr;
+		info.data.full = vdev->msix.table_entries[index].data;
+
+		ret = ptirq_prepare_msix_remap(vpci2vm(vdev->vpci), vdev->bdf.value, pbdf.value,
+			(uint16_t)index, &info, vdev->pdev->irte_start + (uint16_t)index);
+		if (ret == 0) {
+			if (!vdev->msix.is_vmsix_on_msi_programmed) {
+				ir_index.index = vdev->pdev->irte_start;
+				info.addr.ir_bits.shv = 1U;
+				info.addr.ir_bits.intr_index_high = ir_index.bits.index_high;
+				info.addr.ir_bits.intr_index_low = ir_index.bits.index_low;
+				pci_pdev_write_cfg(pbdf, capoff + PCIR_MSI_ADDR, 0x4U, (uint32_t)info.addr.full);
+				if (vdev->msi.is_64bit) {
+					pci_pdev_write_cfg(pbdf, capoff + PCIR_MSI_ADDR_HIGH, 0x4U,
+							(uint32_t)(info.addr.full >> 32U));
+					pci_pdev_write_cfg(pbdf, capoff + PCIR_MSI_DATA_64BIT, 0x2U,
+							(uint16_t)info.data.full);
+				} else {
+					pci_pdev_write_cfg(pbdf, capoff + PCIR_MSI_DATA, 0x2U,
+							(uint16_t)info.data.full);
+				}
+				vdev->msix.is_vmsix_on_msi_programmed = true;
+			}
+			mask_bits &= ~vector_mask;
+		}
+	}
+	pci_pdev_write_cfg(pbdf, get_mask_bits_offset(vdev), 4U, mask_bits);
+}
diff --git a/hypervisor/dm/vpci/vpci.c b/hypervisor/dm/vpci/vpci.c
index 7cbf1172b..bc5c4449a 100644
--- a/hypervisor/dm/vpci/vpci.c
+++ b/hypervisor/dm/vpci/vpci.c
@@ -500,7 +500,11 @@ static int32_t write_pt_dev_cfg(struct pci_vdev *vdev, uint32_t offset,
 	} else if (msicap_access(vdev, offset)) {
 		write_vmsi_cap_reg(vdev, offset, bytes, val);
 	} else if (msixcap_access(vdev, offset)) {
-		write_vmsix_cap_reg(vdev, offset, bytes, val);
+		if (vdev->msix.is_vmsix_on_msi) {
+			write_vmsix_cap_reg_on_msi(vdev, offset, bytes, val);
+		} else {
+			write_vmsix_cap_reg(vdev, offset, bytes, val);
+		}
 	} else if (sriovcap_access(vdev, offset)) {
 		write_sriov_cap_reg(vdev, offset, bytes, val);
 	} else {
diff --git a/hypervisor/dm/vpci/vpci_priv.h b/hypervisor/dm/vpci/vpci_priv.h
index 749678c74..769926a8a 100644
--- a/hypervisor/dm/vpci/vpci_priv.h
+++ b/hypervisor/dm/vpci/vpci_priv.h
@@ -128,6 +128,10 @@ void read_vmsix_cap_reg(const struct pci_vdev *vdev, uint32_t offset, uint32_t b
 void write_vmsix_cap_reg(struct pci_vdev *vdev, uint32_t offset, uint32_t bytes, uint32_t val);
 void deinit_vmsix(struct pci_vdev *vdev);
 
+void init_vmsix_on_msi(struct pci_vdev *vdev);
+void write_vmsix_cap_reg_on_msi(struct pci_vdev *vdev, uint32_t offset, uint32_t bytes, uint32_t val);
+void remap_one_vmsix_entry_on_msi(struct pci_vdev *vdev, uint32_t index);
+
 void init_vsriov(struct pci_vdev *vdev);
 void read_sriov_cap_reg(const struct pci_vdev *vdev, uint32_t offset, uint32_t bytes, uint32_t *val);
 void write_sriov_cap_reg(struct pci_vdev *vdev, uint32_t offset, uint32_t bytes, uint32_t val);
diff --git a/hypervisor/hw/pci.c b/hypervisor/hw/pci.c
index 76dcdd9b4..4e5a2a09a 100644
--- a/hypervisor/hw/pci.c
+++ b/hypervisor/hw/pci.c
@@ -767,6 +767,7 @@ struct pci_pdev *init_pdev(uint16_t pbdf, uint32_t drhd_index)
 
 			pdev->drhd_index = drhd_index;
 			num_pci_pdev++;
+			reserve_vmsix_on_msi_irtes(pdev);
 		} else {
 			pr_err("%s, %x:%x.%x unsupported headed type: 0x%x\n",
 				__func__, bdf.bits.b, bdf.bits.d, bdf.bits.f, hdr_type);
diff --git a/hypervisor/include/dm/vpci.h b/hypervisor/include/dm/vpci.h
index cd3679af2..e0e2f7170 100644
--- a/hypervisor/include/dm/vpci.h
+++ b/hypervisor/include/dm/vpci.h
@@ -67,6 +67,8 @@ struct pci_msix {
 	uint32_t  table_bar;
 	uint32_t  table_offset;
 	uint32_t  table_count;
+	bool      is_vmsix_on_msi;
+	bool	  is_vmsix_on_msi_programmed;
 };
 
 /* SRIOV capability structure */
diff --git a/hypervisor/include/hw/pci.h b/hypervisor/include/hw/pci.h
index 997dc3c81..d18ca728e 100644
--- a/hypervisor/include/hw/pci.h
+++ b/hypervisor/include/hw/pci.h
@@ -228,6 +228,9 @@ struct pci_pdev {
 
 	/* IOMMU responsible for DMA and Interrupt Remapping for this device */
 	uint32_t drhd_index;
+	/* Used for vMSI-x on MSI emulation */
+	uint16_t irte_start;
+	uint16_t irte_count;
 
 	/* The bar info of the physical PCI device. */
 	uint32_t nr_bars; /* 6 for normal device, 2 for bridge, 1 for cardbus */
@@ -359,4 +362,5 @@ bool is_plat_hidden_pdev(union pci_bdf bdf);
 bool pdev_need_bar_restore(const struct pci_pdev *pdev);
 void pdev_restore_bar(const struct pci_pdev *pdev);
 void pci_switch_to_mmio_cfg_ops(void);
+void reserve_vmsix_on_msi_irtes(struct pci_pdev *pdev);
 #endif /* PCI_H_ */