From 21945ae127480c8332c1110ceada2df4a42a5848 Mon Sep 17 00:00:00 2001
From: Liam <byteslice@airmail.cc>
Date: Tue, 5 Jul 2022 23:27:25 -0400
Subject: kernel: fix issues with single core mode

---
 src/core/cpu_manager.cpp | 152 +++++++++++++++++++++++++++++++----------------
 1 file changed, 101 insertions(+), 51 deletions(-)

(limited to 'src/core/cpu_manager.cpp')

diff --git a/src/core/cpu_manager.cpp b/src/core/cpu_manager.cpp
index 428194129..838d6be21 100644
--- a/src/core/cpu_manager.cpp
+++ b/src/core/cpu_manager.cpp
@@ -42,19 +42,19 @@ void CpuManager::Shutdown() {
     }
 }
 
-void CpuManager::GuestActivateFunction() {
+void CpuManager::GuestThreadFunction() {
     if (is_multicore) {
-        MultiCoreGuestActivate();
+        MultiCoreRunGuestThread();
     } else {
-        SingleCoreGuestActivate();
+        SingleCoreRunGuestThread();
     }
 }
 
-void CpuManager::GuestThreadFunction() {
+void CpuManager::IdleThreadFunction() {
     if (is_multicore) {
-        MultiCoreRunGuestThread();
+        MultiCoreRunIdleThread();
     } else {
-        SingleCoreRunGuestThread();
+        SingleCoreRunIdleThread();
     }
 }
 
@@ -62,19 +62,6 @@ void CpuManager::ShutdownThreadFunction() {
     ShutdownThread();
 }
 
-void CpuManager::WaitForAndHandleInterrupt() {
-    auto& kernel = system.Kernel();
-    auto& physical_core = kernel.CurrentPhysicalCore();
-
-    ASSERT(Kernel::GetCurrentThread(kernel).GetDisableDispatchCount() == 1);
-
-    if (!physical_core.IsInterrupted()) {
-        physical_core.Idle();
-    }
-
-    HandleInterrupt();
-}
-
 void CpuManager::HandleInterrupt() {
     auto& kernel = system.Kernel();
     auto core_index = kernel.CurrentPhysicalCoreIndex();
@@ -86,49 +73,121 @@ void CpuManager::HandleInterrupt() {
 ///                             MultiCore                                   ///
 ///////////////////////////////////////////////////////////////////////////////
 
-void CpuManager::MultiCoreGuestActivate() {
-    // Similar to the HorizonKernelMain callback in HOS
+void CpuManager::MultiCoreRunGuestThread() {
+    // Similar to UserModeThreadStarter in HOS
     auto& kernel = system.Kernel();
-    auto* scheduler = kernel.CurrentScheduler();
+    kernel.CurrentScheduler()->OnThreadStart();
 
-    scheduler->Activate();
-    UNREACHABLE();
+    while (true) {
+        auto* physical_core = &kernel.CurrentPhysicalCore();
+        while (!physical_core->IsInterrupted()) {
+            physical_core->Run();
+            physical_core = &kernel.CurrentPhysicalCore();
+        }
+
+        HandleInterrupt();
+    }
 }
 
-void CpuManager::MultiCoreRunGuestThread() {
-    // Similar to UserModeThreadStarter in HOS
+void CpuManager::MultiCoreRunIdleThread() {
+    // Not accurate to HOS. Remove this entire method when singlecore is removed.
+    // See notes in KScheduler::ScheduleImpl for more information about why this
+    // is inaccurate.
+
     auto& kernel = system.Kernel();
-    auto* thread = kernel.GetCurrentEmuThread();
-    thread->EnableDispatch();
+    kernel.CurrentScheduler()->OnThreadStart();
+
+    while (true) {
+        auto& physical_core = kernel.CurrentPhysicalCore();
+        if (!physical_core.IsInterrupted()) {
+            physical_core.Idle();
+        }
 
-    MultiCoreRunGuestLoop();
+        HandleInterrupt();
+    }
 }
 
-void CpuManager::MultiCoreRunGuestLoop() {
+///////////////////////////////////////////////////////////////////////////////
+///                             SingleCore                                   ///
+///////////////////////////////////////////////////////////////////////////////
+
+void CpuManager::SingleCoreRunGuestThread() {
     auto& kernel = system.Kernel();
+    kernel.CurrentScheduler()->OnThreadStart();
 
     while (true) {
         auto* physical_core = &kernel.CurrentPhysicalCore();
-        while (!physical_core->IsInterrupted()) {
+        if (!physical_core->IsInterrupted()) {
             physical_core->Run();
             physical_core = &kernel.CurrentPhysicalCore();
         }
 
+        kernel.SetIsPhantomModeForSingleCore(true);
+        system.CoreTiming().Advance();
+        kernel.SetIsPhantomModeForSingleCore(false);
+
+        PreemptSingleCore();
         HandleInterrupt();
     }
 }
 
-///////////////////////////////////////////////////////////////////////////////
-///                             SingleCore                                   ///
-///////////////////////////////////////////////////////////////////////////////
+void CpuManager::SingleCoreRunIdleThread() {
+    auto& kernel = system.Kernel();
+    kernel.CurrentScheduler()->OnThreadStart();
+
+    while (true) {
+        PreemptSingleCore(false);
+        system.CoreTiming().AddTicks(1000U);
+        idle_count++;
+        HandleInterrupt();
+    }
+}
 
-void CpuManager::SingleCoreGuestActivate() {}
+void CpuManager::PreemptSingleCore(bool from_running_environment) {
+    {
+        auto& kernel = system.Kernel();
+        auto& scheduler = kernel.Scheduler(current_core);
+
+        Kernel::KThread* current_thread = scheduler.GetSchedulerCurrentThread();
+        if (idle_count >= 4 || from_running_environment) {
+            if (!from_running_environment) {
+                system.CoreTiming().Idle();
+                idle_count = 0;
+            }
+            kernel.SetIsPhantomModeForSingleCore(true);
+            system.CoreTiming().Advance();
+            kernel.SetIsPhantomModeForSingleCore(false);
+        }
+        current_core.store((current_core + 1) % Core::Hardware::NUM_CPU_CORES);
+        system.CoreTiming().ResetTicks();
+        scheduler.Unload(scheduler.GetSchedulerCurrentThread());
 
-void CpuManager::SingleCoreRunGuestThread() {}
+        auto& next_scheduler = kernel.Scheduler(current_core);
 
-void CpuManager::SingleCoreRunGuestLoop() {}
+        // Disable dispatch. We're about to preempt this thread.
+        Kernel::KScopedDisableDispatch dd{kernel};
+        Common::Fiber::YieldTo(current_thread->GetHostContext(), *next_scheduler.GetSwitchFiber());
+    }
 
-void CpuManager::PreemptSingleCore(bool from_running_enviroment) {}
+    // We've now been scheduled again, and we may have exchanged schedulers.
+    // Reload the scheduler in case it's different.
+    {
+        auto& scheduler = system.Kernel().Scheduler(current_core);
+        scheduler.Reload(scheduler.GetSchedulerCurrentThread());
+        if (!scheduler.IsIdle()) {
+            idle_count = 0;
+        }
+    }
+}
+
+void CpuManager::GuestActivate() {
+    // Similar to the HorizonKernelMain callback in HOS
+    auto& kernel = system.Kernel();
+    auto* scheduler = kernel.CurrentScheduler();
+
+    scheduler->Activate();
+    UNREACHABLE();
+}
 
 void CpuManager::ShutdownThread() {
     auto& kernel = system.Kernel();
@@ -168,20 +227,11 @@ void CpuManager::RunThread(std::size_t core) {
     }
 
     auto& kernel = system.Kernel();
+    auto& scheduler = *kernel.CurrentScheduler();
+    auto* thread = scheduler.GetSchedulerCurrentThread();
+    Kernel::SetCurrentThread(kernel, thread);
 
-    auto* main_thread = Kernel::KThread::Create(kernel);
-    main_thread->SetName(fmt::format("MainThread:{}", core));
-    ASSERT(Kernel::KThread::InitializeMainThread(system, main_thread, static_cast<s32>(core))
-               .IsSuccess());
-
-    auto* idle_thread = Kernel::KThread::Create(kernel);
-    ASSERT(Kernel::KThread::InitializeIdleThread(system, idle_thread, static_cast<s32>(core))
-               .IsSuccess());
-
-    kernel.SetCurrentEmuThread(main_thread);
-    kernel.CurrentScheduler()->Initialize(idle_thread);
-
-    Common::Fiber::YieldTo(data.host_context, *main_thread->GetHostContext());
+    Common::Fiber::YieldTo(data.host_context, *thread->GetHostContext());
 }
 
 } // namespace Core
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