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

[Liav Albani <liavalb@gmail.com>]

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 +++++++++
 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).
+     */
+    fadt.iapc_boot_arch = object_resolve_path_type("", TYPE_I8042, NULL) ?
+                            0x0002 : 0x0000;
+
     *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;
+
     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 */
 
     /*
-- 
2.35.1