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

[Ani Sinha]

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.

> +        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.

> +
> +    /* 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
>
>