Re: [PATCH v2 2/2] hw/acpi: add indication for i8042 in IA-PC boot flags of the FADT table

[Ani Sinha]

On Mon, 21 Feb 2022, Liav Albani wrote:

> This can allow the guest OS to determine more easily if i8042 controller
> is present in the system or not, so it doesn't need to do probing of the
> controller, but just initialize it immediately, before enumerating the
> ACPI AML namespace.
>
> Signed-off-by: Liav Albani <liavalb@gmail.com>
> ---
>  hw/acpi/aml-build.c         | 7 ++++++-
>  hw/i386/acpi-build.c        | 5 +++++
>  hw/i386/acpi-microvm.c      | 5 +++++
>  include/hw/acpi/acpi-defs.h | 1 +
>  4 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> index 8966e16320..ef5f4cad87 100644
> --- a/hw/acpi/aml-build.c
> +++ b/hw/acpi/aml-build.c
> @@ -2152,7 +2152,12 @@ void build_fadt(GArray *tbl, BIOSLinker *linker, const 
> AcpiFadtData *f,
>      build_append_int_noprefix(tbl, 0, 1); /* DAY_ALRM */
>      build_append_int_noprefix(tbl, 0, 1); /* MON_ALRM */
>      build_append_int_noprefix(tbl, f->rtc_century, 1); /* CENTURY */
> -    build_append_int_noprefix(tbl, 0, 2); /* IAPC_BOOT_ARCH */
> +    /* IAPC_BOOT_ARCH */
> +    if (f->rev == 1) {
> +        build_append_int_noprefix(tbl, 0, 2);
> +    } else {
> +        build_append_int_noprefix(tbl, f->iapc_boot_arch, 2);
> +    }

So your change will only apply for q35 machines and not for pc types. You
should write a comment saying that this is not defined in acpi spec 1.0
where revision == 1 also applies.
I see that IAPC boot arch is defined as
old as ACPI version 2:

https://uefi.org/sites/default/files/resources/ACPI_2.pdf
Section 5.2.8

On a unrelatd note, I see FADT revision is hardcoded to 3 even as old as
ACPI version 2. *Except* in ACPI version 1b, it is hardcoded to 1 which
w2k seems to like :-) (table 5-5 in
https://uefi.org/sites/default/files/resources/ACPI_1_Errata_B.pdf) .
I will add a comment in the code related to this.


>      build_append_int_noprefix(tbl, 0, 1); /* Reserved */
>      build_append_int_noprefix(tbl, f->flags, 4); /* Flags */
>
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index ebd47aa26f..5dc625b8d8 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -192,6 +192,11 @@ static void init_common_fadt_data(MachineState *ms, 
> Object *o,
>              .address = object_property_get_uint(o, ACPI_PM_PROP_GPE0_BLK, 
> NULL)
>          },
>      };
> +    if (isa_check_device_existence("i8042")) {
> +        /* Indicates if i8042 is present or not */
> +        fadt.iapc_boot_arch = (1 << 1);
> +    }
> +
>      *data = fadt;
>  }
>
> diff --git a/hw/i386/acpi-microvm.c b/hw/i386/acpi-microvm.c
> index 68ca7e7fc2..756c69b3b0 100644
> --- a/hw/i386/acpi-microvm.c
> +++ b/hw/i386/acpi-microvm.c
> @@ -189,6 +189,11 @@ static void acpi_build_microvm(AcpiBuildTables *tables,
>          .reset_val = ACPI_GED_RESET_VALUE,
>      };
>
> +    if (isa_check_device_existence("i8042")) {
> +        /* Indicates if i8042 is present or not */
> +        pmfadt.iapc_boot_arch = (1 << 1);
> +    }
> +
>      table_offsets = g_array_new(false, true /* clear */,
>                                          sizeof(uint32_t));


We should do the same thing for arm architecture as well?
hw/arm/virt-acpi-build.c .


>      bios_linker_loader_alloc(tables->linker,
> diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
> index c97e8633ad..2b42e4192b 100644
> --- a/include/hw/acpi/acpi-defs.h
> +++ b/include/hw/acpi/acpi-defs.h
> @@ -77,6 +77,7 @@ typedef struct AcpiFadtData {
>      uint16_t plvl2_lat;        /* P_LVL2_LAT */
>      uint16_t plvl3_lat;        /* P_LVL3_LAT */
>      uint16_t arm_boot_arch;    /* ARM_BOOT_ARCH */
> +    uint16_t iapc_boot_arch;   /* IAPC_BOOT_ARCH */
>      uint8_t minor_ver;         /* FADT Minor Version */
>
>      /*
> --
> 2.35.1
>
>