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

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 1 Mar 2022 06:19:51 -0500
"Michael S. Tsirkin" <mst@redhat.com> 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?
> >   
> > >  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:
I don't do that  and don't ask it from others.

The reason being that pointing where to look in spec and having
verbatim copy of field name is sufficient for looking it up and
QEMU does not endup with half of spec copied in (+unintentional mistakes).
(As reviewer I will check if whatever written in patch actually matches
spec anyways)

That's why I typically use
  'spec ver, verbatim field name[, chapter/table name]'
policy. The later optional part is usually used for pointing
to values description.
 
> /* 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 */
> > >  
> > >      /*  
>