Re: [PATCH v4 2/3] hw/acpi: add indication for i8042 in IA-PC boot flags of the FADT table

[Liav Albani]

On 3/1/22 13:19, Michael S. Tsirkin wrote:
> On Tue, Mar 01, 2022 at 09:43:54AM +0100, Igor Mammedov wrote:
> > On Mon, 28 Feb 2022 22:17:32 +0200
> > Liav Albani <liavalb@gmail.com> 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.
> > >
> > > This change only applies to the x86/q35 machine type, as it uses FACP
> > > ACPI table with revision higher than 1, which should implement at least
> > > ACPI 2.0 features within the table, hence it can also set the IA-PC boot
> > > flags register according to the ACPI 2.0 specification.
> > >
> > > Signed-off-by: Liav Albani <liavalb@gmail.com>
> > > ---
> > >   hw/acpi/aml-build.c         | 11 ++++++++++-
> > >   hw/i386/acpi-build.c        |  9 +++++++++
> > >   hw/i386/acpi-microvm.c      |  9 +++++++++
> > commit message says it's q35 specific, so wy it touched microvm anc piix4?
This affect only q35 machine type for now, but what happens if the 
MicroVM ACPI FACP table is updated to use a revision that supports IA-PC 
boot flags?
> > >   include/hw/acpi/acpi-defs.h |  1 +
> > >   4 files changed, 29 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> > > index 8966e16320..2085905b83 100644
> > > --- a/hw/acpi/aml-build.c
> > > +++ b/hw/acpi/aml-build.c
> > > @@ -2152,7 +2152,16 @@ 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 */
> > > +    /*
> > > +     * This register is not defined in ACPI spec version 1.0, where the FACP
> > > +     * revision == 1 also applies. Therefore, just ignore setting this 
> > > register.
> > > +     */
> > > +    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..c72c7bb9bb 100644
> > > --- a/hw/i386/acpi-build.c
> > > +++ b/hw/i386/acpi-build.c
> > > @@ -38,6 +38,7 @@
> > >   #include "hw/nvram/fw_cfg.h"
> > >   #include "hw/acpi/bios-linker-loader.h"
> > >   #include "hw/isa/isa.h"
> > > +#include "hw/input/i8042.h"
> > >   #include "hw/block/fdc.h"
> > >   #include "hw/acpi/memory_hotplug.h"
> > >   #include "sysemu/tpm.h"
> > > @@ -192,6 +193,14 @@ 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 of the IAPC_BOOT_ARCH register indicates i8042 presence
> > > +     * or equivalent micro controller. See table 5-10 of APCI spec version 2.0
> > > +     * (the earliest acpi revision that supports this).
> >   /* APCI spec version 2.0, Table 5-10 */
> >
> > is sufficient, the rest could be read from spec/
> ACPI though, not APCI.
It will be fixed in version 5.
> The comment can be shorter and more clearer, but I feel quoting spec
> and including table name is a good idea actually, but pls quote verbatim:
>
> /* ACPI spec version 2.0, Table 5-10: Fixed ACPI Description Table Boot 
> Architecture Flags */
> /* Bit offset 1 -  port 60 and 64 based keyboard controller, usually 
> implemented as an 8042 or equivalent micro-controller. */
>
> > > +     */
> > > +    fadt.iapc_boot_arch = object_resolve_path_type("", TYPE_I8042, NULL) ?
> > > +                            0x0002 : 0x0000;
> and make it 0x1 << 1 - clearer that this is bit 1. Leading zeroes are
> not helpful since compiler does not check there's a correct number of
> these.
It will be fixed in version 5.
> > > +
> > >       *data = fadt;
> > >   }
> > >   
> > > diff --git a/hw/i386/acpi-microvm.c b/hw/i386/acpi-microvm.c
> > > index 68ca7e7fc2..4bc72b1672 100644
> > > --- a/hw/i386/acpi-microvm.c
> > > +++ b/hw/i386/acpi-microvm.c
> > > @@ -31,6 +31,7 @@
> > >   #include "hw/acpi/generic_event_device.h"
> > >   #include "hw/acpi/utils.h"
> > >   #include "hw/acpi/erst.h"
> > > +#include "hw/input/i8042.h"
> > >   #include "hw/i386/fw_cfg.h"
> > >   #include "hw/i386/microvm.h"
> > >   #include "hw/pci/pci.h"
> > > @@ -189,6 +190,14 @@ static void acpi_build_microvm(AcpiBuildTables *tables,
> > >           .reset_val = ACPI_GED_RESET_VALUE,
> > >       };
> > >   
> > > +    /*
> > > +     * second bit of 16 of the IAPC_BOOT_ARCH register indicates i8042 presence
> > > +     * or equivalent micro controller. See table 5-10 of APCI spec version 2.0
> > > +     * (the earliest acpi revision that supports this).
> > > +     */
> > > +    pmfadt.iapc_boot_arch = object_resolve_path_type("", TYPE_I8042, NULL) ?
> > > +                            0x0002 : 0x0000;
> > > +
> let's avoid code duplication pls.
What do you suggest to do with this? Creating a separate function to do 
this for us so we can call it from both locations?
> > >       table_offsets = g_array_new(false, true /* clear */,
> > >                                           sizeof(uint32_t));
> > >       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 */
> > >   
> > >       /*