[Qemu-devel] [PATCH v4 3/5] acpi: pc: add fw_cfg device node to ssdt

["Gabriel L. Somlo" <somlo@cmu.edu>]

Add a fw_cfg device node to the ACPI SSDT, on machine types
pc-*-2.5 and up. While the guest-side BIOS can't utilize
this information (since it has to access the hard-coded
fw_cfg device to extract ACPI tables to begin with), having
fw_cfg listed in ACPI will help the guest kernel keep a more
accurate inventory of in-use IO port regions.

Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
---
 hw/i386/acpi-build.c | 23 +++++++++++++++++++++++
 hw/i386/pc_piix.c    |  1 +
 hw/i386/pc_q35.c     |  1 +
 include/hw/i386/pc.h |  1 +
 4 files changed, 26 insertions(+)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 95e0c65..ece2710 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -906,6 +906,7 @@ build_ssdt(GArray *table_data, GArray *linker,
            PcPciInfo *pci, PcGuestInfo *guest_info)
 {
     MachineState *machine = MACHINE(qdev_get_machine());
+    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(machine);
     uint32_t nr_mem = machine->ram_slots;
     unsigned acpi_cpus = guest_info->apic_id_limit;
     Aml *ssdt, *sb_scope, *scope, *pkg, *dev, *method, *crs, *field, *ifctx;
@@ -1071,6 +1072,28 @@ build_ssdt(GArray *table_data, GArray *linker,
     aml_append(scope, aml_name_decl("_S5", pkg));
     aml_append(ssdt, scope);
 
+    if (!pcmc->acpi_no_fw_cfg_node) {
+        scope = aml_scope("\\_SB");
+        dev = aml_device("FWCF");
+
+        aml_append(dev, aml_name_decl("_HID", aml_string("QEMU0002")));
+        /* device present, functioning, decoding, not shown in UI */
+        aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));
+
+        crs = aml_resource_template();
+        /* when using port i/o, the 8-bit data register *always* overlaps
+         * with half of the 16-bit control register. Hence, the total size
+         * of the i/o region used is FW_CFG_CTL_SIZE */
+        aml_append(crs,
+            aml_io(AML_DECODE16, FW_CFG_IO_BASE, FW_CFG_IO_BASE,
+                   0x01, FW_CFG_CTL_SIZE)
+        );
+        aml_append(dev, aml_name_decl("_CRS", crs));
+
+        aml_append(scope, dev);
+        aml_append(ssdt, scope);
+    }
+
     if (misc->applesmc_io_base) {
         scope = aml_scope("\\_SB.PCI0.ISA");
         dev = aml_device("SMC");
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 3ffb05f..7f5e5d9 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -482,6 +482,7 @@ static void pc_i440fx_2_4_machine_options(MachineClass *m)
     m->alias = NULL;
     m->is_default = 0;
     pcmc->broken_reserved_end = true;
+    pcmc->acpi_no_fw_cfg_node = true;
     SET_MACHINE_COMPAT(m, PC_COMPAT_2_4);
 }
 
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 1b7d3b6..7180ca3 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -385,6 +385,7 @@ static void pc_q35_2_4_machine_options(MachineClass *m)
     pc_q35_2_5_machine_options(m);
     m->alias = NULL;
     pcmc->broken_reserved_end = true;
+    pcmc->acpi_no_fw_cfg_node = true;
     SET_MACHINE_COMPAT(m, PC_COMPAT_2_4);
 }
 
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 86007e3..6d0f1bd 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -62,6 +62,7 @@ struct PCMachineClass {
     bool broken_reserved_end;
     HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
                                            DeviceState *dev);
+    bool acpi_no_fw_cfg_node;
 };
 
 #define TYPE_PC_MACHINE "generic-pc-machine"
-- 
2.4.3