1 files changed, 53 insertions, 4 deletions

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index ebc5f03..d90c471 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -25,7 +25,9 @@
 #include <glib.h>
 #include "qemu-common.h"
 #include "qemu/bitmap.h"
+#include "qemu/osdep.h"
 #include "qemu/range.h"
+#include "qemu/error-report.h"
 #include "hw/pci/pci.h"
 #include "qom/cpu.h"
 #include "hw/i386/pc.h"
@@ -52,6 +54,14 @@
 #include "qapi/qmp/qint.h"
 #include "qom/qom-qobject.h"
 
+/* These are used to size the ACPI tables for -M pc-i440fx-1.7 and
+ * -M pc-i440fx-2.0.  Even if the actual amount of AML generated grows
+ * a little bit, there should be plenty of free space since the DSDT
+ * shrunk by ~1.5k between QEMU 2.0 and QEMU 2.1.
+ */
+#define ACPI_BUILD_LEGACY_CPU_AML_SIZE    97
+#define ACPI_BUILD_ALIGN_SIZE             0x1000
+
 typedef struct AcpiCpuInfo {
     DECLARE_BITMAP(found_cpus, ACPI_CPU_HOTPLUG_ID_LIMIT);
 } AcpiCpuInfo;
@@ -1440,13 +1450,14 @@ static
 void acpi_build(PcGuestInfo *guest_info, AcpiBuildTables *tables)
 {
     GArray *table_offsets;
-    unsigned facs, dsdt, rsdt;
+    unsigned facs, ssdt, dsdt, rsdt;
     AcpiCpuInfo cpu;
     AcpiPmInfo pm;
     AcpiMiscInfo misc;
     AcpiMcfgInfo mcfg;
     PcPciInfo pci;
     uint8_t *u;
+    size_t aml_len = 0;
 
     acpi_get_cpu_info(&cpu);
     acpi_get_pm_info(&pm);
@@ -1474,13 +1485,20 @@ void acpi_build(PcGuestInfo *guest_info, AcpiBuildTables *tables)
     dsdt = tables->table_data->len;
     build_dsdt(tables->table_data, tables->linker, &misc);
 
+    /* Count the size of the DSDT and SSDT, we will need it for legacy
+     * sizing of ACPI tables.
+     */
+    aml_len += tables->table_data->len - dsdt;
+
     /* ACPI tables pointed to by RSDT */
     acpi_add_table(table_offsets, tables->table_data);
     build_fadt(tables->table_data, tables->linker, &pm, facs, dsdt);
 
+    ssdt = tables->table_data->len;
     acpi_add_table(table_offsets, tables->table_data);
     build_ssdt(tables->table_data, tables->linker, &cpu, &pm, &misc, &pci,
                guest_info);
+    aml_len += tables->table_data->len - ssdt;
 
     acpi_add_table(table_offsets, tables->table_data);
     build_madt(tables->table_data, tables->linker, &cpu, guest_info);
@@ -1513,14 +1531,45 @@ void acpi_build(PcGuestInfo *guest_info, AcpiBuildTables *tables)
     /* RSDP is in FSEG memory, so allocate it separately */
     build_rsdp(tables->rsdp, tables->linker, rsdt);
 
-    /* We'll expose it all to Guest so align size to reduce
+    /* We'll expose it all to Guest so we want to reduce
      * chance of size changes.
      * RSDP is small so it's easy to keep it immutable, no need to
      * bother with alignment.
+     *
+     * We used to align the tables to 4k, but of course this would
+     * too simple to be enough.  4k turned out to be too small an
+     * alignment very soon, and in fact it is almost impossible to
+     * keep the table size stable for all (max_cpus, max_memory_slots)
+     * combinations.  So the table size is always 64k for pc-i440fx-2.1
+     * and we give an error if the table grows beyond that limit.
+     *
+     * We still have the problem of migrating from "-M pc-i440fx-2.0".  For
+     * that, we exploit the fact that QEMU 2.1 generates _smaller_ tables
+     * than 2.0 and we can always pad the smaller tables with zeros.  We can
+     * then use the exact size of the 2.0 tables.
+     *
+     * All this is for PIIX4, since QEMU 2.0 didn't support Q35 migration.
      */
-    acpi_align_size(tables->table_data, 0x1000);
+    if (guest_info->legacy_acpi_table_size) {
+        /* Subtracting aml_len gives the size of fixed tables.  Then add the
+         * size of the PIIX4 DSDT/SSDT in QEMU 2.0.
+         */
+        int legacy_aml_len =
+            guest_info->legacy_acpi_table_size +
+            ACPI_BUILD_LEGACY_CPU_AML_SIZE * max_cpus;
+        int legacy_table_size =
+            ROUND_UP(tables->table_data->len - aml_len + legacy_aml_len,
+                     ACPI_BUILD_ALIGN_SIZE);
+        if (tables->table_data->len > legacy_table_size) {
+            /* Should happen only with PCI bridges and -M pc-i440fx-2.0.  */
+            error_report("Warning: migration to QEMU 2.0 may not work.");
+        }
+        g_array_set_size(tables->table_data, legacy_table_size);
+    } else {
+        acpi_align_size(tables->table_data, ACPI_BUILD_ALIGN_SIZE);
+    }
 
-    acpi_align_size(tables->linker, 0x1000);
+    acpi_align_size(tables->linker, ACPI_BUILD_ALIGN_SIZE);
 
     /* Cleanup memory that's no longer used. */
     g_array_free(table_offsets, true);