diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
index cd5c49616e..28cb97b60f 100644
--- a/hw/pci-host/q35.c
+++ b/hw/pci-host/q35.c
@@ -134,7 +134,7 @@ static void q35_host_get_mmcfg_size(Object *obj, Visitor *v, const char *name,
     visit_type_uint32(v, name, &value, errp);
 }
 
-static Property mch_props[] = {
+static Property q35_host_props[] = {
     DEFINE_PROP_UINT64(PCIE_HOST_MCFG_BASE, Q35PCIHost, parent_obj.base_addr,
                         MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT),
     DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, Q35PCIHost,
@@ -154,7 +154,7 @@ static void q35_host_class_init(ObjectClass *klass, void *data)
 
     hc->root_bus_path = q35_host_root_bus_path;
     dc->realize = q35_host_realize;
-    dc->props = mch_props;
+    dc->props = q35_host_props;
     /* Reason: needs to be wired up by pc_q35_init */
     dc->user_creatable = false;
     set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
@@ -369,7 +369,7 @@ static void mch_update_smram(MCHPCIState *mch)
             tseg_size = 1024 * 1024 * 8;
             break;
         default:
-            tseg_size = 0;
+            tseg_size = 1024 * 1024 * (uint32_t)mch->ext_tseg_mbytes;
             break;
         }
     } else {
@@ -392,6 +392,17 @@ static void mch_update_smram(MCHPCIState *mch)
     memory_region_transaction_commit();
 }
 
+static void mch_update_ext_tseg_mbytes(MCHPCIState *mch)
+{
+    PCIDevice *pd = PCI_DEVICE(mch);
+    uint8_t *reg = pd->config + MCH_HOST_BRIDGE_EXT_TSEG_MBYTES;
+
+    if (mch->ext_tseg_mbytes > 0 &&
+        pci_get_word(reg) == MCH_HOST_BRIDGE_EXT_TSEG_MBYTES_QUERY) {
+        pci_set_word(reg, mch->ext_tseg_mbytes);
+    }
+}
+
 static void mch_write_config(PCIDevice *d,
                               uint32_t address, uint32_t val, int len)
 {
@@ -413,6 +424,11 @@ static void mch_write_config(PCIDevice *d,
                        MCH_HOST_BRIDGE_SMRAM_SIZE)) {
         mch_update_smram(mch);
     }
+
+    if (ranges_overlap(address, len, MCH_HOST_BRIDGE_EXT_TSEG_MBYTES,
+                       MCH_HOST_BRIDGE_EXT_TSEG_MBYTES_SIZE)) {
+        mch_update_ext_tseg_mbytes(mch);
+    }
 }
 
 static void mch_update(MCHPCIState *mch)
@@ -420,6 +436,7 @@ static void mch_update(MCHPCIState *mch)
     mch_update_pciexbar(mch);
     mch_update_pam(mch);
     mch_update_smram(mch);
+    mch_update_ext_tseg_mbytes(mch);
 }
 
 static int mch_post_load(void *opaque, int version_id)
@@ -457,6 +474,11 @@ static void mch_reset(DeviceState *qdev)
     d->wmask[MCH_HOST_BRIDGE_SMRAM] = MCH_HOST_BRIDGE_SMRAM_WMASK;
     d->wmask[MCH_HOST_BRIDGE_ESMRAMC] = MCH_HOST_BRIDGE_ESMRAMC_WMASK;
 
+    if (mch->ext_tseg_mbytes > 0) {
+        pci_set_word(d->config + MCH_HOST_BRIDGE_EXT_TSEG_MBYTES,
+                     MCH_HOST_BRIDGE_EXT_TSEG_MBYTES_QUERY);
+    }
+
     mch_update(mch);
 }
 
@@ -465,6 +487,12 @@ static void mch_realize(PCIDevice *d, Error **errp)
     int i;
     MCHPCIState *mch = MCH_PCI_DEVICE(d);
 
+    if (mch->ext_tseg_mbytes > MCH_HOST_BRIDGE_EXT_TSEG_MBYTES_MAX) {
+        error_setg(errp, "invalid extended-tseg-mbytes value: %" PRIu16,
+                   mch->ext_tseg_mbytes);
+        return;
+    }
+
     /* setup pci memory mapping */
     pc_pci_as_mapping_init(OBJECT(mch), mch->system_memory,
                            mch->pci_address_space);
@@ -530,6 +558,12 @@ uint64_t mch_mcfg_base(void)
     return MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT;
 }
 
+static Property mch_props[] = {
+    DEFINE_PROP_UINT16("extended-tseg-mbytes", MCHPCIState, ext_tseg_mbytes,
+                       16),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void mch_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
@@ -538,6 +572,7 @@ static void mch_class_init(ObjectClass *klass, void *data)
     k->realize = mch_realize;
     k->config_write = mch_write_config;
     dc->reset = mch_reset;
+    dc->props = mch_props;
     set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
     dc->desc = "Host bridge";
     dc->vmsd = &vmstate_mch;
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index d071c9c0e9..233216abdc 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -384,6 +384,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
 
 #define PC_COMPAT_2_9 \
     HW_COMPAT_2_9 \
+    {\
+        .driver   = "mch",\
+        .property = "extended-tseg-mbytes",\
+        .value    = stringify(0),\
+    },\
 
 #define PC_COMPAT_2_8 \
     HW_COMPAT_2_8 \
diff --git a/include/hw/pci-host/q35.h b/include/hw/pci-host/q35.h
index 53b6760c16..58983c00b3 100644
--- a/include/hw/pci-host/q35.h
+++ b/include/hw/pci-host/q35.h
@@ -60,6 +60,7 @@ typedef struct MCHPCIState {
     uint64_t above_4g_mem_size;
     uint64_t pci_hole64_size;
     uint32_t short_root_bus;
+    uint16_t ext_tseg_mbytes;
 } MCHPCIState;
 
 typedef struct Q35PCIHost {
@@ -91,6 +92,11 @@ typedef struct Q35PCIHost {
 /* D0:F0 configuration space */
 #define MCH_HOST_BRIDGE_REVISION_DEFAULT       0x0
 
+#define MCH_HOST_BRIDGE_EXT_TSEG_MBYTES        0x50
+#define MCH_HOST_BRIDGE_EXT_TSEG_MBYTES_SIZE   2
+#define MCH_HOST_BRIDGE_EXT_TSEG_MBYTES_QUERY  0xffff
+#define MCH_HOST_BRIDGE_EXT_TSEG_MBYTES_MAX    0xfff
+
 #define MCH_HOST_BRIDGE_PCIEXBAR               0x60    /* 64bit register */
 #define MCH_HOST_BRIDGE_PCIEXBAR_SIZE          8       /* 64bit register */
 #define MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT       0xb0000000