diff --git a/hypervisor/arch/x86/vtd.c b/hypervisor/arch/x86/vtd.c
index a57b60e29..8b31fc7e8 100644
--- a/hypervisor/arch/x86/vtd.c
+++ b/hypervisor/arch/x86/vtd.c
@@ -275,6 +275,11 @@ static void iommu_flush_cache(const struct dmar_drhd_rt *dmar_unit,
 }
 
 #if DBG_IOMMU
+static inline uint8_t iommu_cap_rwbf(uint64_t cap)
+{
+	return ((uint8_t)(cap >> 4U) & 1U);
+}
+
 static void dmar_unit_show_capability(struct dmar_drhd_rt *dmar_unit)
 {
 	pr_info("dmar unit[0x%x]", dmar_unit->drhd->reg_base_addr);
@@ -486,20 +491,6 @@ static struct dmar_drhd_rt *device_to_dmaru(uint16_t segment, uint8_t bus, uint8
 	return dmar_unit;
 }
 
-static void dmar_write_buffer_flush(struct dmar_drhd_rt *dmar_unit)
-{
-	uint32_t status;
-
-	if (iommu_cap_rwbf(dmar_unit->cap) != 0U) {
-		spinlock_obtain(&(dmar_unit->lock));
-		iommu_write32(dmar_unit, DMAR_GCMD_REG, dmar_unit->gcmd | DMA_GCMD_WBF);
-
-		/* read lower 32 bits to check */
-		dmar_wait_completion(dmar_unit, DMAR_GSTS_REG, DMA_GSTS_WBFS, true, &status);
-		spinlock_release(&(dmar_unit->lock));
-	}
-}
-
 /*
  * did: domain id
  * sid: source id
@@ -799,7 +790,6 @@ static void dmar_prepare(struct dmar_drhd_rt *dmar_unit)
 static void dmar_enable(struct dmar_drhd_rt *dmar_unit)
 {
 	dev_dbg(ACRN_DBG_IOMMU, "enable dmar uint [0x%x]", dmar_unit->drhd->reg_base_addr);
-	dmar_write_buffer_flush(dmar_unit);
 	dmar_invalid_context_cache_global(dmar_unit);
 	dmar_invalid_iotlb_global(dmar_unit);
 	dmar_enable_translation(dmar_unit);
@@ -815,8 +805,6 @@ static void dmar_suspend(struct dmar_drhd_rt *dmar_unit)
 {
 	uint32_t i;
 
-	/* flush */
-	dmar_write_buffer_flush(dmar_unit);
 	dmar_invalid_context_cache_global(dmar_unit);
 	dmar_invalid_iotlb_global(dmar_unit);
 
diff --git a/hypervisor/include/arch/x86/vtd.h b/hypervisor/include/arch/x86/vtd.h
index 12787b6c3..22ce67040 100644
--- a/hypervisor/include/arch/x86/vtd.h
+++ b/hypervisor/include/arch/x86/vtd.h
@@ -129,11 +129,6 @@ static inline uint8_t iommu_cap_plmr(uint64_t cap)
 	return ((uint8_t)(cap >> 5U) & 1U);
 }
 
-static inline uint8_t iommu_cap_rwbf(uint64_t cap)
-{
-	return ((uint8_t)(cap >> 4U) & 1U);
-}
-
 static inline uint8_t iommu_cap_afl(uint64_t cap)
 {
 	return ((uint8_t)(cap >> 3U) & 1U);