hw/i386/acpi: Remove PCMachineClass::legacy_acpi_table_size

PCMachineClass::legacy_acpi_table_size was only used by the
pc-i440fx-2.0 machine, which got removed. Remove it and simplify
acpi_build().

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20240617071118.60464-6-philmd@linaro.org>

hw/i386/acpi-build.c

@@ -85,7 +85,6 @@
  * 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
 
 #define ACPI_BUILD_TABLE_SIZE             0x20000
@@ -2499,13 +2498,12 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
     X86MachineState *x86ms = X86_MACHINE(machine);
     DeviceState *iommu = pcms->iommu;
     GArray *table_offsets;
-    unsigned facs, dsdt, rsdt, fadt;
+    unsigned facs, dsdt, rsdt;
     AcpiPmInfo pm;
     AcpiMiscInfo misc;
     AcpiMcfgInfo mcfg;
     Range pci_hole = {}, pci_hole64 = {};
     uint8_t *u;
-    size_t aml_len = 0;
     GArray *tables_blob = tables->table_data;
     AcpiSlicOem slic_oem = { .id = NULL, .table_id = NULL };
     Object *vmgenid_dev;
@@ -2551,19 +2549,12 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
     build_dsdt(tables_blob, tables->linker, &pm, &misc,
                &pci_hole, &pci_hole64, machine);
 
-    /* Count the size of the DSDT and SSDT, we will need it for legacy
-     * sizing of ACPI tables.
-     */
-    aml_len += tables_blob->len - dsdt;
-
     /* ACPI tables pointed to by RSDT */
-    fadt = tables_blob->len;
     acpi_add_table(table_offsets, tables_blob);
     pm.fadt.facs_tbl_offset = &facs;
     pm.fadt.dsdt_tbl_offset = &dsdt;
     pm.fadt.xdsdt_tbl_offset = &dsdt;
     build_fadt(tables_blob, tables->linker, &pm.fadt, oem_id, oem_table_id);
-    aml_len += tables_blob->len - fadt;
 
     acpi_add_table(table_offsets, tables_blob);
     acpi_build_madt(tables_blob, tables->linker, x86ms,
@@ -2694,49 +2685,19 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
      * 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
+     * combinations.
-     * 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.
      */
-    if (pcmc->legacy_acpi_table_size) {
+    /* Make sure we have a buffer in case we need to resize the tables. */
-        /* Subtracting aml_len gives the size of fixed tables.  Then add the
+    if ((tables_blob->len > ACPI_BUILD_TABLE_SIZE / 2) &&
-         * size of the PIIX4 DSDT/SSDT in QEMU 2.0.
+        !pcmc->resizable_acpi_blob) {
-         */
+        /* As of QEMU 2.1, this fires with 160 VCPUs and 255 memory slots.  */
-        int legacy_aml_len =
+        warn_report("ACPI table size %u exceeds %d bytes,"
-            pcmc->legacy_acpi_table_size +
+                    " migration may not work",
-            ACPI_BUILD_LEGACY_CPU_AML_SIZE * x86ms->apic_id_limit;
+                    tables_blob->len, ACPI_BUILD_TABLE_SIZE / 2);
-        int legacy_table_size =
+        error_printf("Try removing CPUs, NUMA nodes, memory slots"
-            ROUND_UP(tables_blob->len - aml_len + legacy_aml_len,
+                     " or PCI bridges.\n");
-                     ACPI_BUILD_ALIGN_SIZE);
-        if ((tables_blob->len > legacy_table_size) &&
-            !pcmc->resizable_acpi_blob) {
-            /* Should happen only with PCI bridges and -M pc-i440fx-2.0.  */
-            warn_report("ACPI table size %u exceeds %d bytes,"
-                        " migration may not work",
-                        tables_blob->len, legacy_table_size);
-            error_printf("Try removing CPUs, NUMA nodes, memory slots"
-                         " or PCI bridges.\n");
-        }
-        g_array_set_size(tables_blob, legacy_table_size);
-    } else {
-        /* Make sure we have a buffer in case we need to resize the tables. */
-        if ((tables_blob->len > ACPI_BUILD_TABLE_SIZE / 2) &&
-            !pcmc->resizable_acpi_blob) {
-            /* As of QEMU 2.1, this fires with 160 VCPUs and 255 memory slots.  */
-            warn_report("ACPI table size %u exceeds %d bytes,"
-                        " migration may not work",
-                        tables_blob->len, ACPI_BUILD_TABLE_SIZE / 2);
-            error_printf("Try removing CPUs, NUMA nodes, memory slots"
-                         " or PCI bridges.\n");
-        }
-        acpi_align_size(tables_blob, ACPI_BUILD_TABLE_SIZE);
     }
+    acpi_align_size(tables_blob, ACPI_BUILD_TABLE_SIZE);
 
     acpi_align_size(tables->linker->cmd_blob, ACPI_BUILD_ALIGN_SIZE);
 

include/hw/i386/pc.h

@@ -103,7 +103,6 @@ struct PCMachineClass {
     /* ACPI compat: */
     bool has_acpi_build;
     bool rsdp_in_ram;
-    int legacy_acpi_table_size;
     unsigned acpi_data_size;
     int pci_root_uid;