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 09:11:09PM +0200, Liav Albani wrote:
> 
> 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?

Sounds reasonable.

> > > >       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 */
> > > >       /*