diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 06b48b3172..b90de6c664 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -1710,6 +1710,9 @@ static void vtd_root_table_setup(IntelIOMMUState *s)
 {
     s->root = vtd_get_quad_raw(s, DMAR_RTADDR_REG);
     s->root_extended = s->root & VTD_RTADDR_RTT;
+    if (s->scalable_mode) {
+        s->root_scalable = s->root & VTD_RTADDR_SMT;
+    }
     s->root &= VTD_RTADDR_ADDR_MASK(s->aw_bits);
 
     trace_vtd_reg_dmar_root(s->root, s->root_extended);
@@ -2419,6 +2422,17 @@ static bool vtd_process_inv_desc(IntelIOMMUState *s)
         }
         break;
 
+    /*
+     * TODO: the entity of below two cases will be implemented in future series.
+     * To make guest (which integrates scalable mode support patch set in
+     * iommu driver) work, just return true is enough so far.
+     */
+    case VTD_INV_DESC_PC:
+        break;
+
+    case VTD_INV_DESC_PIOTLB:
+        break;
+
     case VTD_INV_DESC_WAIT:
         trace_vtd_inv_desc("wait", inv_desc.hi, inv_desc.lo);
         if (!vtd_process_wait_desc(s, &inv_desc)) {
@@ -2983,6 +2997,7 @@ static Property vtd_properties[] = {
     DEFINE_PROP_UINT8("aw-bits", IntelIOMMUState, aw_bits,
                       VTD_HOST_ADDRESS_WIDTH),
     DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode, FALSE),
+    DEFINE_PROP_BOOL("x-scalable-mode", IntelIOMMUState, scalable_mode, FALSE),
     DEFINE_PROP_BOOL("dma-drain", IntelIOMMUState, dma_drain, true),
     DEFINE_PROP_END_OF_LIST(),
 };
@@ -3518,6 +3533,11 @@ static void vtd_init(IntelIOMMUState *s)
         s->cap |= VTD_CAP_CM;
     }
 
+    /* TODO: read cap/ecap from host to decide which cap to be exposed. */
+    if (s->scalable_mode) {
+        s->ecap |= VTD_ECAP_SMTS | VTD_ECAP_SRS | VTD_ECAP_SLTS;
+    }
+
     vtd_reset_caches(s);
 
     /* Define registers with default values and bit semantics */
@@ -3629,6 +3649,11 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
         return false;
     }
 
+    if (s->scalable_mode && !s->dma_drain) {
+        error_setg(errp, "Need to set dma_drain for scalable mode");
+        return false;
+    }
+
     return true;
 }
 
diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index 016fa4c7c5..1160618177 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -190,7 +190,9 @@
 #define VTD_ECAP_EIM                (1ULL << 4)
 #define VTD_ECAP_PT                 (1ULL << 6)
 #define VTD_ECAP_MHMV               (15ULL << 20)
+#define VTD_ECAP_SRS                (1ULL << 31)
 #define VTD_ECAP_SMTS               (1ULL << 43)
+#define VTD_ECAP_SLTS               (1ULL << 46)
 
 /* CAP_REG */
 /* (offset >> 4) << 24 */
@@ -345,6 +347,8 @@ typedef union VTDInvDesc VTDInvDesc;
 #define VTD_INV_DESC_IEC                0x4 /* Interrupt Entry Cache
                                                Invalidate Descriptor */
 #define VTD_INV_DESC_WAIT               0x5 /* Invalidation Wait Descriptor */
+#define VTD_INV_DESC_PIOTLB             0x6 /* PASID-IOTLB Invalidate Desc */
+#define VTD_INV_DESC_PC                 0x7 /* PASID-cache Invalidate Desc */
 #define VTD_INV_DESC_NONE               0   /* Not an Invalidate Descriptor */
 
 /* Masks for Invalidation Wait Descriptor*/
diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index 2877c94ca2..c11e3d5b34 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -227,7 +227,8 @@ struct IntelIOMMUState {
     uint8_t womask[DMAR_REG_SIZE];  /* WO (write only - read returns 0) */
     uint32_t version;
 
-    bool caching_mode;          /* RO - is cap CM enabled? */
+    bool caching_mode;              /* RO - is cap CM enabled? */
+    bool scalable_mode;             /* RO - is Scalable Mode supported? */
 
     dma_addr_t root;                /* Current root table pointer */
     bool root_extended;             /* Type of root table (extended or not) */