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

[Anirban Sinha]

> On 28-Mar-2023, at 5:46 PM, Igor Mammedov <imammedo@redhat.com> wrote:
> 
> 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.

Hmm, initially I thought q35 was unaffected but seems I was mistaken. Looking 
at 94dec5948aeb240 ("pc: rename machine types”), seems q35 machine types 
started with version 1.4 and so any version earlier than 2.3 in q35 should also 
be affected. I will take care of this.

 
> 
>> 
>> 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

Sure, will rename accordingly.

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