Re: [PATCH-for-9.1 05/18] hw/i386/acpi: Remove PCMachineClass::legacy_acpi_table_size

[Thomas Huth]

On 05/03/2024 14.42, Philippe Mathieu-Daudé wrote:
> PCMachineClass::legacy_acpi_table_size was only used by the
> pc-i440fx-2.0 machine, which got removed. Remove it and simplify
> acpi_build().
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/i386/pc.h |  1 -
>   hw/i386/acpi-build.c | 60 +++++++++-----------------------------------
>   2 files changed, 12 insertions(+), 49 deletions(-)
>
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 3360ca2307..758d670a36 100644
> --- a/include/hw/i386/pc.h
> +++ b/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;
>   
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 15242b9096..8c7fad92e9 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2496,13 +2496,12 @@ 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;
> @@ -2548,19 +2547,12 @@ 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,
> @@ -2691,49 +2683,21 @@ 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
> -     * 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.
> +     * combinations.
>        *
>        * All this is for PIIX4, since QEMU 2.0 didn't support Q35 migration.

I think you could remove this "All this is for ..." sentence now, too?

 Thomas


>        */
> -    if (pcmc->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 =
> -            pcmc->legacy_acpi_table_size +
> -            ACPI_BUILD_LEGACY_CPU_AML_SIZE * x86ms->apic_id_limit;
> -        int legacy_table_size =
> -            ROUND_UP(tables_blob->len - aml_len + legacy_aml_len,
> -                     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);
> +    /* 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->linker->cmd_blob, ACPI_BUILD_ALIGN_SIZE);
>