Re: [External] : Re: [RFC PATCH 2/4] acpi: fadt: support revision 6.0 of the ACPI specification

[Miguel Luis]

Hi Ani,

> On 7 Oct 2022, at 04:25, Ani Sinha <ani@anisinha.ca> wrote:
> 
> 
> 
> On Thu, 6 Oct 2022, Miguel Luis wrote:
> 
>> Update the Fixed ACPI Description Table (FADT) to revision 6.0 of the ACPI
>> specification adding the field "Hypervisor Vendor Identity" that was missing.
>> 
>> This field's description states the following: "64-bit identifier of 
>> hypervisor
>> vendor. All bytes in this field are considered part of the vendor identity.
>> These identifiers are defined independently by the vendors themselves,
>> usually following the name of the hypervisor product. Version information
>> should NOT be included in this field - this shall simply denote the vendor's
>> name or identifier. Version information can be communicated through a
>> supplemental vendor-specific hypervisor API. Firmware implementers would
>> place zero bytes into this field, denoting that no hypervisor is present in
>> the actual firmware."
>> 
>> Hereupon, what should a valid identifier of an Hypervisor Vendor ID be and
>> where should QEMU provide that information?
>> 
>> On this RFC there's the suggestion of having this information in sync by the
>> current acceleration name. This also seems to imply that QEMU, which 
>> generates
>> the FADT table, and the FADT consumer need to be in sync with the values of 
>> this
>> field.
>> 
>> Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
>> ---
>> hw/acpi/aml-build.c      | 14 +++++++++++---
>> hw/arm/virt-acpi-build.c | 10 +++++-----
>> 2 files changed, 16 insertions(+), 8 deletions(-)
>> 
>> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
>> index e6bfac95c7..5258c4ac64 100644
>> --- a/hw/acpi/aml-build.c
>> +++ b/hw/acpi/aml-build.c
>> @@ -31,6 +31,7 @@
>> #include "hw/pci/pci_bus.h"
>> #include "hw/pci/pci_bridge.h"
>> #include "qemu/cutils.h"
>> +#include "qemu/accel.h"
>> 
>> static GArray *build_alloc_array(void)
>> {
>> @@ -2070,7 +2071,7 @@ void build_pptt(GArray *table_data, BIOSLinker 
>> *linker, MachineState *ms,
>>     acpi_table_end(linker, &table);
>> }
>> 
>> -/* build rev1/rev3/rev5.1 FADT */
>> +/* build rev1/rev3/rev5.1/rev6.0 FADT */
>> void build_fadt(GArray *tbl, BIOSLinker *linker, const AcpiFadtData *f,
>>                 const char *oem_id, const char *oem_table_id)
>> {
>> @@ -2193,8 +2194,15 @@ void build_fadt(GArray *tbl, BIOSLinker *linker, 
>> const AcpiFadtData *f,
>>     /* SLEEP_STATUS_REG */
>>     build_append_gas_from_struct(tbl, &f->sleep_sts);
>> 
>> -    /* TODO: extra fields need to be added to support revisions above rev5 
>> */
>> -    assert(f->rev == 5);
>> +    if (f->rev <= 5) {
> 
> <= does not make sense. It should be f->rev == 5.
> The previous code compares f->rev <= 4 since it needs to cover revisions
> 2, 3 and 4.
> 

Indeed, that’s right. I will fix.

>> +        goto done;
>> +    }
>> +
>> +    /* Hypervisor Vendor Identity */
>> +    build_append_padded_str(tbl, current_accel_name(), 8, '\0');
> 
> I do not think the vendor identity should change based on the accelerator.
> The accelerator QEMU uses should be hidden from the guest OS as far as
> possible. I would suggest a string like "QEMU" for vendor ID.
> 

Thank you for the suggestion Ani. I will spin the next version with it.

Thanks,
Miguel

>> +
>> +    /* TODO: extra fields need to be added to support revisions above rev6 
>> */
>> +    assert(f->rev == 6);
>> 
>> done:
>>     acpi_table_end(linker, &table);
>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>> index 9b3aee01bf..72bb6f61a5 100644
>> --- a/hw/arm/virt-acpi-build.c
>> +++ b/hw/arm/virt-acpi-build.c
>> @@ -809,13 +809,13 @@ build_madt(GArray *table_data, BIOSLinker *linker, 
>> VirtMachineState *vms)
>> }
>> 
>> /* FADT */
>> -static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
>> +static void build_fadt_rev6(GArray *table_data, BIOSLinker *linker,
>>                             VirtMachineState *vms, unsigned dsdt_tbl_offset)
>> {
>> -    /* ACPI v5.1 */
>> +    /* ACPI v6.0 */
>>     AcpiFadtData fadt = {
>> -        .rev = 5,
>> -        .minor_ver = 1,
>> +        .rev = 6,
>> +        .minor_ver = 0,
>>         .flags = 1 << ACPI_FADT_F_HW_REDUCED_ACPI,
>>         .xdsdt_tbl_offset = &dsdt_tbl_offset,
>>     };
>> @@ -945,7 +945,7 @@ void virt_acpi_build(VirtMachineState *vms, 
>> AcpiBuildTables *tables)
>> 
>>     /* FADT MADT PPTT GTDT MCFG SPCR DBG2 pointed to by RSDT */
>>     acpi_add_table(table_offsets, tables_blob);
>> -    build_fadt_rev5(tables_blob, tables->linker, vms, dsdt);
>> +    build_fadt_rev6(tables_blob, tables->linker, vms, dsdt);
>> 
>>     acpi_add_table(table_offsets, tables_blob);
>>     build_madt(tables_blob, tables->linker, vms);
>> --
>> 2.37.3
>> 
>>