Re: [PATCH v3 3/4] hw/acpi: add indication for i8042 in IA-PC boot flags of the FADT table

[Liav Albani]

On 2/27/22 12:48, Bernhard Beschow wrote:
> Am 26. Februar 2022 06:30:18 UTC schrieb Liav Albani <liavalb@gmail.com>:
> > 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        | 8 ++++++++
> > hw/i386/acpi-microvm.c      | 9 +++++++++
> > include/hw/acpi/acpi-defs.h | 1 +
> > 4 files changed, 24 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);
> > +    }
> >      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..65dbc1ec36 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -192,6 +192,14 @@ static void init_common_fadt_data(MachineState *ms, Object 
> > *o,
> >              .address = object_property_get_uint(o, ACPI_PM_PROP_GPE0_BLK, NULL)
> >          },
> >      };
> > +    /*
> > +     * second bit of 16 but IAPC_BOOT_ARCH indicates presence of 8042 or
> > +     * equivalent micro controller. See table 5-10 of APCI spec version 2.0
> > +     * (the earliest acpi revision that supports this).
> > +     */
> > +
> > +    fadt.iapc_boot_arch = isa_check_device_existence("i8042") ? 0x0002 : 
> > 0x0000;
> Couldn't qdev_find_recursive() be used here instead? This would also make patch 
> 1 unneccessary. Same below.
>
> Best regards
> Bernhard

I tried it first, but because it tries to find the ID of a device 
instead of a type (I look for i8042 type which is a string of the device 
type), it didn't work as expected. We don't compare DeviceState id, but 
ObjectClass type->name here :)

With my patch we could just find the device without any problem whatsoever.

Best regards,
Liav