[RFC PATCH v2 2/5] hw/pci-bridge: add Thunderbolt PCIe-to-PCI bridge

[Dmitry R <rdmitry0911@gmail.com>]

Add thunderbolt-pcie-pci-bridge for PCI endpoints tunnelled through the
Thunderbolt PCIe layer. The bridge exposes Thunderbolt-related ACPI
properties while leaving downstream PCI devices as regular QEMU devices.

Signed-off-by: Dmitry R <rdmitry0911@gmail.com>
---
 hw/pci-bridge/meson.build                   |   1 +
 hw/pci-bridge/thunderbolt_pcie_pci_bridge.c | 156 ++++++++++++++++++++
 2 files changed, 157 insertions(+)
 create mode 100644 hw/pci-bridge/thunderbolt_pcie_pci_bridge.c

diff --git a/hw/pci-bridge/meson.build b/hw/pci-bridge/meson.build
index fd0698fb33..8bb58ec84c 100644
--- a/hw/pci-bridge/meson.build
+++ b/hw/pci-bridge/meson.build
@@ -5,6 +5,7 @@ pci_ss.add(when: 'CONFIG_IOH3420', if_true: files('ioh3420.c'))
 pci_ss.add(when: 'CONFIG_PCIE_PORT', if_true: files('pcie_root_port.c', 'gen_pcie_root_port.c'))
 pci_ss.add(when: 'CONFIG_PCIE_PORT', if_true: files('thunderbolt_root_port.c'))
 pci_ss.add(when: 'CONFIG_PCIE_PCI_BRIDGE', if_true: files('pcie_pci_bridge.c'))
+pci_ss.add(when: 'CONFIG_PCIE_PCI_BRIDGE', if_true: files('thunderbolt_pcie_pci_bridge.c'))
 pci_ss.add(when: 'CONFIG_PXB', if_true: files('pci_expander_bridge.c'),
                                if_false: files('pci_expander_bridge_stubs.c'))
 pci_ss.add(when: 'CONFIG_XIO3130', if_true: files('xio3130_upstream.c', 'xio3130_downstream.c'))
diff --git a/hw/pci-bridge/thunderbolt_pcie_pci_bridge.c b/hw/pci-bridge/thunderbolt_pcie_pci_bridge.c
new file mode 100644
index 0000000000..afbf4871f4
--- /dev/null
+++ b/hw/pci-bridge/thunderbolt_pcie_pci_bridge.c
@@ -0,0 +1,156 @@
+/*
+ * Thunderbolt PCI Express to PCI Bridge
+ *
+ * This is the regular generic PCIe-to-PCI bridge used as a Thunderbolt PCIe
+ * tunnel endpoint. Downstream PCI devices are described normally so existing
+ * macOS drivers that are not IOPCITunnelCompatible can still bind to them.
+ *
+ * Copyright (C) 2026
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/module.h"
+#include "hw/acpi/aml-build.h"
+#include "hw/acpi/pcihp.h"
+#include "hw/acpi/acpi_aml_interface.h"
+#include "hw/pci/pci.h"
+#include "hw/pci/pci_bridge.h"
+#include "qom/object.h"
+
+#define TYPE_THUNDERBOLT_PCIE_PCI_BRIDGE "thunderbolt-pcie-pci-bridge"
+
+static Aml *build_device_properties_dsd(Aml *properties)
+{
+    Aml *dsd;
+
+    dsd = aml_package(2);
+    aml_append(dsd, aml_touuid("DAFFD814-6EBA-4D8C-8A91-BC9BBF4AA301"));
+    aml_append(dsd, properties);
+
+    return aml_name_decl("_DSD", dsd);
+}
+
+static void append_bool_property(Aml *properties, const char *name)
+{
+    Aml *property = aml_package(2);
+
+    aml_append(property, aml_string("%s", name));
+    aml_append(property, aml_int(1));
+    aml_append(properties, property);
+}
+
+static void build_tunnelled_device_dsd(Aml *scope)
+{
+    Aml *properties = aml_package(1);
+
+    append_bool_property(properties, "IOPCITunnelled");
+
+    aml_append(scope, build_device_properties_dsd(properties));
+}
+
+static void build_tunnelled_device_acpi_properties(Aml *scope)
+{
+    build_tunnelled_device_dsd(scope);
+}
+
+static Aml *build_pci_static_endpoint_dsm(PCIDevice *pdev)
+{
+    Aml *method;
+    Aml *params;
+    Aml *pkg;
+
+    g_assert(pdev->acpi_index != 0);
+
+    method = aml_method("_DSM", 4, AML_SERIALIZED);
+    params = aml_local(0);
+    pkg = aml_package(1);
+    aml_append(pkg, aml_int(pdev->acpi_index));
+    aml_append(method, aml_store(pkg, params));
+    aml_append(method,
+        aml_return(aml_call5("EDSM", aml_arg(0), aml_arg(1), aml_arg(2),
+                             aml_arg(3), params)));
+
+    return method;
+}
+
+static bool thunderbolt_bridge_devfn_ignored(int devfn, const PCIBus *bus)
+{
+    const PCIDevice *pdev = bus->devices[devfn];
+
+    if (PCI_FUNC(devfn) && IS_PCI_BRIDGE(pdev) && DEVICE(pdev)->hotplugged) {
+        return true;
+    }
+
+    return false;
+}
+
+static void build_tunnelled_pci_bus_devices(Aml *parent_scope, PCIBus *bus)
+{
+    int devfn;
+
+    for (devfn = 0; devfn < ARRAY_SIZE(bus->devices); devfn++) {
+        PCIDevice *pdev = bus->devices[devfn];
+        int adr = PCI_SLOT(devfn) << 16 | PCI_FUNC(devfn);
+        Aml *dev;
+
+        if (!pdev || thunderbolt_bridge_devfn_ignored(devfn, bus)) {
+            continue;
+        }
+
+        dev = aml_device("S%.02X", devfn);
+        aml_append(dev, aml_name_decl("_ADR", aml_int(adr)));
+
+        call_dev_aml_func(DEVICE(pdev), dev);
+
+        if (pdev->acpi_index &&
+            !object_property_get_bool(OBJECT(pdev), "hotpluggable",
+                                      &error_abort)) {
+            aml_append(dev, build_pci_static_endpoint_dsm(pdev));
+        }
+
+        aml_append(parent_scope, dev);
+    }
+}
+
+static void build_thunderbolt_pcie_pci_bridge_aml(AcpiDevAmlIf *adev,
+                                                  Aml *scope)
+{
+    PCIBridge *br = PCI_BRIDGE(adev);
+
+    build_tunnelled_device_acpi_properties(scope);
+
+    if (!DEVICE(br)->hotplugged) {
+        PCIBus *sec_bus = pci_bridge_get_sec_bus(br);
+
+        build_tunnelled_pci_bus_devices(scope, sec_bus);
+
+        if (object_property_find(OBJECT(sec_bus), ACPI_PCIHP_PROP_BSEL)) {
+            build_append_pcihp_slots(scope, sec_bus);
+        }
+    }
+}
+
+static void thunderbolt_pcie_pci_bridge_class_init(ObjectClass *klass,
+                                                   const void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    AcpiDevAmlIfClass *adevc = ACPI_DEV_AML_IF_CLASS(klass);
+
+    dc->desc = "Thunderbolt PCI Express to PCI Bridge";
+    adevc->build_dev_aml = build_thunderbolt_pcie_pci_bridge_aml;
+}
+
+static const TypeInfo thunderbolt_pcie_pci_bridge_info = {
+    .name       = TYPE_THUNDERBOLT_PCIE_PCI_BRIDGE,
+    .parent     = "pcie-pci-bridge",
+    .class_init = thunderbolt_pcie_pci_bridge_class_init,
+};
+
+static void thunderbolt_pcie_pci_bridge_register_types(void)
+{
+    type_register_static(&thunderbolt_pcie_pci_bridge_info);
+}
+
+type_init(thunderbolt_pcie_pci_bridge_register_types)
-- 
2.47.3