Re: [PATCH v2 3/3] hw/i386/acpi-build: Resolve north rather than south bridges

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 28 Oct 2022 12:34:19 +0200
Bernhard Beschow <shentey@gmail.com> wrote:

> The code currently assumes Q35 iff ICH9 and i440fx iff PIIX. Now that more
> AML generation has been moved into the south bridges and since the
> machines define themselves primarily through their north bridges, let's
> switch to resolving the north bridges for AML generation instead. This
> also allows for easier experimentation with different south bridges in
> the "pc" machine, e.g. with PIIX4 and VT82xx.

Patch looks fine to me in a sense that either would work.

But the commit message lacks clear answer to 'why'
and what issues it resolves or would resolve/make
our easier life down to road.

> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> ---
>  hw/i386/acpi-build.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 73d8a59737..d9eaa5fc4d 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -60,6 +60,7 @@
>  #include "hw/i386/fw_cfg.h"
>  #include "hw/i386/ich9.h"
>  #include "hw/pci/pci_bus.h"
> +#include "hw/pci-host/i440fx.h"
>  #include "hw/pci-host/q35.h"
>  #include "hw/i386/x86-iommu.h"
>  
> @@ -1322,8 +1323,8 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>             AcpiPmInfo *pm, AcpiMiscInfo *misc,
>             Range *pci_hole, Range *pci_hole64, MachineState *machine)
>  {
> -    Object *piix = object_resolve_type_unambiguous(TYPE_PIIX4_PM);
> -    Object *lpc = object_resolve_type_unambiguous(TYPE_ICH9_LPC_DEVICE);
> +    Object *i440fx = object_resolve_type_unambiguous(TYPE_I440FX_PCI_HOST_BRIDGE);
> +    Object *q35 = object_resolve_type_unambiguous(TYPE_Q35_HOST_DEVICE);
>      CrsRangeEntry *entry;
>      Aml *dsdt, *sb_scope, *scope, *dev, *method, *field, *pkg, *crs;
>      CrsRangeSet crs_range_set;
> @@ -1344,13 +1345,13 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>      AcpiTable table = { .sig = "DSDT", .rev = 1, .oem_id = x86ms->oem_id,
>                          .oem_table_id = x86ms->oem_table_id };
>  
> -    assert(!!piix != !!lpc);
> +    assert(!!i440fx != !!q35);
>  
>      acpi_table_begin(&table, table_data);
>      dsdt = init_aml_allocator();
>  
>      build_dbg_aml(dsdt);
> -    if (piix) {
> +    if (i440fx) {
>          sb_scope = aml_scope("_SB");
>          dev = aml_device("PCI0");
>          aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03")));
> @@ -1363,7 +1364,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>              build_x86_acpi_pci_hotplug(dsdt, pm->pcihp_io_base);
>          }
>          build_piix4_pci0_int(dsdt);
> -    } else if (lpc) {
> +    } else if (q35) {
>          sb_scope = aml_scope("_SB");
>          dev = aml_device("PCI0");
>          aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A08")));