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

["Michael S. Tsirkin" <mst@redhat.com>]

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?
> 
> >  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.
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.

> > +
> >      *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.

> >      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 */
> >  
> >      /*