From 36248bb63a396dfea762d5b2cf028bf4b7a2b62e Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Tue, 28 Jul 2026 13:09:08 +0200
Subject: x86_64: split lapic according to UDM

---
 arch/x86_64/kapi/cpu.cpp     | 54 --------------------------------------------
 arch/x86_64/kapi/devices.cpp | 31 +++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 54 deletions(-)

(limited to 'arch/x86_64/kapi')

diff --git a/arch/x86_64/kapi/cpu.cpp b/arch/x86_64/kapi/cpu.cpp
index 100f53df..2bec841c 100644
--- a/arch/x86_64/kapi/cpu.cpp
+++ b/arch/x86_64/kapi/cpu.cpp
@@ -1,32 +1,14 @@
 #include <kapi/cpu.hpp>
 
 #include <arch/cpu/initialization.hpp>
-#include <arch/devices/local_apic.hpp>
 
-#include <kapi/acpi.hpp>
-#include <kapi/devices.hpp>
-#include <kapi/devices/cpu.hpp>
-#include <kapi/memory.hpp>
 #include <kapi/system.hpp>
 
-#include <acpi/acpi.hpp>
-
-#include <kstd/memory.hpp>
-#include <kstd/print.hpp>
-
 #include <atomic>
-#include <ranges>
-#include <utility>
 
 namespace kapi::cpu
 {
 
-  namespace
-  {
-    constexpr auto candidate_flags = ::acpi::processor_local_apic_entry::flags::processor_enabled  //
-                                     | ::acpi::processor_local_apic_entry::flags::online_capable;
-  }
-
   auto init() -> void
   {
     auto static constinit is_initialized = std::atomic_flag{};
@@ -46,42 +28,6 @@ namespace kapi::cpu
     __builtin_unreachable();
   }
 
-  auto discover_topology() -> bool
-  {
-    auto madt = kapi::acpi::get_table<::acpi::table_signature_v<::acpi::madt>>();
-    if (!madt)
-    {
-      kstd::println("[x86_64:PLT] Failed to find ACPI APIC table");
-      return false;
-    }
-
-    auto lapic_entries = *madt | std::views::filter([](auto const & entry) {
-      return entry.type() == ::acpi::madt_entry::type::processor_local_apic;
-    }) | std::views::transform([](auto const & entry) {
-      return static_cast<::acpi::processor_local_apic_entry const &>(entry);
-    }) | std::views::filter([](auto const & entry) { return static_cast<bool>(entry.flags() & candidate_flags); });
-
-    auto bsp_found = false;
-    auto core_index = 0uz;
-    auto local_apic_address = memory::physical_address{madt->local_interrupt_controller_address()};
-    auto cpu_bus = kstd::make_shared<devices::cpu>();
-
-    for (auto const & apic : lapic_entries)
-    {
-      auto is_bsp = !bsp_found;
-      bsp_found = true;
-      auto core = kstd::make_shared<devices::cpu::core>(core_index, apic.processor_id(), is_bsp);
-      core->add_child(kstd::make_shared<arch::devices::local_apic>(core_index, apic.id(), local_apic_address, is_bsp));
-      cpu_bus->add_child(std::move(core));
-      ++core_index;
-    }
-
-    devices::get_root_bus()->add_child(std::move(cpu_bus));
-
-    kstd::println("[x86_64:PLT] Found {} CPU cores", core_index);
-    return core_index > 0;
-  }
-
   auto current_id() -> id
   {
     // TODO: implement actual ID reading once APs are being set up.
diff --git a/arch/x86_64/kapi/devices.cpp b/arch/x86_64/kapi/devices.cpp
index 748e0a6a..04b6fa2d 100644
--- a/arch/x86_64/kapi/devices.cpp
+++ b/arch/x86_64/kapi/devices.cpp
@@ -1,11 +1,21 @@
 #include <kapi/devices.hpp>
 
+#include <arch/bus/cpu.hpp>
 #include <arch/devices/init.hpp>
 #include <arch/drivers/init.hpp>
 
+#include <kapi/system.hpp>
+
+#include <kstd/memory.hpp>
+
 namespace kapi::devices
 {
 
+  namespace
+  {
+    auto static constinit cpu_bus = kstd::shared_ptr<arch::bus::cpu>{};
+  }
+
   auto init_platform_drivers() -> void
   {
     arch::drivers::init_legacy_drivers();
@@ -17,4 +27,25 @@ namespace kapi::devices
     arch::devices::init_legacy_devices();
   }
 
+  auto get_cpu_bus() -> kstd::shared_ptr<bus>
+  {
+    if (!cpu_bus)
+    {
+      system::panic("[x86_64:DEV] The CPU topology has not yet been initialized!");
+    }
+
+    return cpu_bus;
+  }
+
+  auto discover_cpu_topology() -> void
+  {
+    if (cpu_bus)
+    {
+      system::panic("[x86_64:DEV] The CPU topology has already been initialized!");
+    }
+
+    cpu_bus = kstd::make_shared<arch::bus::cpu>();
+    cpu_bus->facet<kapi::devices::bus_protocol>()->enumerate(*cpu_bus);
+  }
+
 }  // namespace kapi::devices
\ No newline at end of file
-- 
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