[RFC,01/14] pc: acpi: x2APIC support for MADT table

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 93f7b5b..668b6bc 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -338,24 +338,38 @@  build_fadt(GArray *table_data, GArray *linker, AcpiPmInfo *pm,
 void pc_madt_cpu_entry(AcpiDeviceIf *adev, int uid,
                        CPUArchIdList *apic_ids, GArray *entry)
 {
-    int apic_id;
-    AcpiMadtProcessorApic *apic = acpi_data_push(entry, sizeof *apic);
-
-    apic_id = apic_ids->cpus[uid].arch_id;
-    apic->type = ACPI_APIC_PROCESSOR;
-    apic->length = sizeof(*apic);
-    apic->processor_id = uid;
-    apic->local_apic_id = apic_id;
-    if (apic_ids->cpus[uid].cpu != NULL) {
-        apic->flags = cpu_to_le32(1);
+    uint32_t apic_id = apic_ids->cpus[uid].arch_id;
+
+    /* ACPI spec says that LAPIC entry for non present
+     * CPU may be omitted from MADT or it must be marked
+     * as disabled. However omitting non present CPU from
+     * MADT breaks hotplug on linux. So possible CPUs
+     * should be put in MADT but kept disabled.
+     */
+    if (apic_id < 255) {
+        AcpiMadtProcessorApic *apic = acpi_data_push(entry, sizeof *apic);
+
+        apic->type = ACPI_APIC_PROCESSOR;
+        apic->length = sizeof(*apic);
+        apic->processor_id = uid;
+        apic->local_apic_id = apic_id;
+        if (apic_ids->cpus[uid].cpu != NULL) {
+            apic->flags = cpu_to_le32(1);
+        } else {
+            apic->flags = cpu_to_le32(0);
+        }
     } else {
-        /* ACPI spec says that LAPIC entry for non present
-         * CPU may be omitted from MADT or it must be marked
-         * as disabled. However omitting non present CPU from
-         * MADT breaks hotplug on linux. So possible CPUs
-         * should be put in MADT but kept disabled.
-         */
-        apic->flags = cpu_to_le32(0);
+        AcpiMadtProcessorX2Apic *apic = acpi_data_push(entry, sizeof *apic);
+
+        apic->type = ACPI_APIC_LOCAL_X2APIC;
+        apic->length = sizeof(*apic);
+        apic->uid = uid;
+        apic->x2apic_id = apic_id;
+        if (apic_ids->cpus[uid].cpu != NULL) {
+            apic->flags = cpu_to_le32(1);
+        } else {
+            apic->flags = cpu_to_le32(0);
+        }
     }
 }
 
@@ -367,11 +381,11 @@  build_madt(GArray *table_data, GArray *linker, PCMachineState *pcms)
     int madt_start = table_data->len;
     AcpiDeviceIfClass *adevc = ACPI_DEVICE_IF_GET_CLASS(pcms->acpi_dev);
     AcpiDeviceIf *adev = ACPI_DEVICE_IF(pcms->acpi_dev);
+    bool x2apic_mode = false;
 
     AcpiMultipleApicTable *madt;
     AcpiMadtIoApic *io_apic;
     AcpiMadtIntsrcovr *intsrcovr;
-    AcpiMadtLocalNmi *local_nmi;
     int i;
 
     madt = acpi_data_push(table_data, sizeof *madt);
@@ -380,6 +394,9 @@  build_madt(GArray *table_data, GArray *linker, PCMachineState *pcms)
 
     for (i = 0; i < apic_ids->len; i++) {
         adevc->madt_cpu(adev, i, apic_ids, table_data);
+        if (apic_ids->cpus[i].arch_id > 254) {
+            x2apic_mode = true;
+        }
     }
     g_free(apic_ids);
 
@@ -413,12 +430,25 @@  build_madt(GArray *table_data, GArray *linker, PCMachineState *pcms)
         intsrcovr->flags  = cpu_to_le16(0xd); /* active high, level triggered */
     }
 
-    local_nmi = acpi_data_push(table_data, sizeof *local_nmi);
-    local_nmi->type         = ACPI_APIC_LOCAL_NMI;
-    local_nmi->length       = sizeof(*local_nmi);
-    local_nmi->processor_id = 0xff; /* all processors */
-    local_nmi->flags        = cpu_to_le16(0);
-    local_nmi->lint         = 1; /* ACPI_LINT1 */
+    if (x2apic_mode) {
+        AcpiMadtLocalX2ApicNmi *local_nmi;
+
+        local_nmi = acpi_data_push(table_data, sizeof *local_nmi);
+        local_nmi->type   = ACPI_APIC_LOCAL_X2APIC_NMI;
+        local_nmi->length = sizeof(*local_nmi);
+        local_nmi->uid    = 0xFFFFFFFF; /* all processors */
+        local_nmi->flags  = cpu_to_le16(0);
+        local_nmi->lint   = 1; /* ACPI_LINT1 */
+    } else {
+        AcpiMadtLocalNmi *local_nmi;
+
+        local_nmi = acpi_data_push(table_data, sizeof *local_nmi);
+        local_nmi->type         = ACPI_APIC_LOCAL_NMI;
+        local_nmi->length       = sizeof(*local_nmi);
+        local_nmi->processor_id = 0xff; /* all processors */
+        local_nmi->flags        = cpu_to_le16(0);
+        local_nmi->lint         = 1; /* ACPI_LINT1 */
+    }
 
     build_header(linker, table_data,
                  (void *)(table_data->data + madt_start), "APIC",
diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
index c7a03d4..a821248 100644
--- a/include/hw/acpi/acpi-defs.h
+++ b/include/hw/acpi/acpi-defs.h
@@ -342,6 +342,25 @@  struct AcpiMadtLocalNmi {
 } QEMU_PACKED;
 typedef struct AcpiMadtLocalNmi AcpiMadtLocalNmi;
 
+struct AcpiMadtProcessorX2Apic
+{
+    ACPI_SUB_HEADER_DEF
+    uint16_t reserved;
+    uint32_t x2apic_id;              /* Processor's local x2APIC ID */
+    uint32_t flags;
+    uint32_t uid;                    /* Processor object _UID */
+} QEMU_PACKED;
+typedef struct AcpiMadtProcessorX2Apic AcpiMadtProcessorX2Apic;
+
+struct AcpiMadtLocalX2ApicNmi {
+    ACPI_SUB_HEADER_DEF
+    uint16_t flags;                  /* MPS INTI flags */
+    uint32_t uid;                    /* Processor object _UID */
+    uint8_t  lint;                   /* Local APIC LINT# */
+    uint8_t  reserved[3];            /* Local APIC LINT# */
+} QEMU_PACKED;
+typedef struct AcpiMadtLocalX2ApicNmi AcpiMadtLocalX2ApicNmi;
+
 struct AcpiMadtGenericInterrupt {
     ACPI_SUB_HEADER_DEF
     uint16_t reserved;