Re: [PATCH] hw/acpi: limit warning on acpi table size to pc machines older than version 2.3

[Igor Mammedov]

On Mon, 20 Mar 2023 16:59:02 +0530
Ani Sinha <anisinha@redhat.com> wrote:

> i440fx machine versions 2.3 and newer and q35 machines supports dynamic ram
> resizing. Please see commit a1666142db6233 ("acpi-build: make ROMs RAM blocks 
> resizeable") .
> Hence the warning when the ACPI table size exceeds a pre-defined value does
> not apply to those machines. Add a check limiting the warning message to only
> those machines that does not support expandable ram blocks, that is, i440fx
> machines with version 2.2 and older.
So q35 is not affected at all? If yes, then mention it here.

> 
> Signed-off-by: Ani Sinha <anisinha@redhat.com>
> ---
>  hw/i386/acpi-build.c | 6 ++++--
>  hw/i386/pc.c         | 1 +
>  hw/i386/pc_piix.c    | 1 +
>  include/hw/i386/pc.h | 3 +++
>  4 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index b19fb4259e..2311bea082 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2616,7 +2616,8 @@ void acpi_build(AcpiBuildTables *tables, MachineState 
> *machine)
>          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) {
> +        if ((tables_blob->len > legacy_table_size) &&
> +            !pcmc->resizable_ram_block) {
>              /* 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",
> @@ -2627,7 +2628,8 @@ void acpi_build(AcpiBuildTables *tables, MachineState 
> *machine)
>          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) {
> +        if ((tables_blob->len > ACPI_BUILD_TABLE_SIZE / 2) &&
> +            !pcmc->resizable_ram_block) {
>              /* 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",
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 7bebea57e3..822d5de333 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1936,6 +1936,7 @@ static void pc_machine_class_init(ObjectClass *oc, void 
> *data)
>      pcmc->acpi_data_size = 0x20000 + 0x8000;
>      pcmc->pvh_enabled = true;
>      pcmc->kvmclock_create_always = true;
> +    pcmc->resizable_ram_block = true;
>      assert(!mc->get_hotplug_handler);
>      mc->get_hotplug_handler = pc_get_hotplug_handler;
>      mc->hotplug_allowed = pc_hotplug_allowed;
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 2f16011bab..3c74dfcfb4 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -745,6 +745,7 @@ static void pc_i440fx_2_2_machine_options(MachineClass *m)
>      compat_props_add(m->compat_props, hw_compat_2_2, hw_compat_2_2_len);
>      compat_props_add(m->compat_props, pc_compat_2_2, pc_compat_2_2_len);
>      pcmc->rsdp_in_ram = false;
> +    pcmc->resizable_ram_block = false;
>  }
>  
>  DEFINE_I440FX_MACHINE(v2_2, "pc-i440fx-2.2", pc_compat_2_2_fn,
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 8206d5405a..3427a35f73 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -127,6 +127,9 @@ struct PCMachineClass {
>  
>      /* create kvmclock device even when KVM PV features are not exposed */
>      bool kvmclock_create_always;
> +
> +    /* resizable memory block compat */
> +    bool resizable_ram_block;
perhaps more specific
   resizeable_acpi_blob
would be better

>  };
>  
>  #define TYPE_PC_MACHINE "generic-pc-machine"