Kernel/Process: Fixed scheduling multiple processes in the SysCore using Dynarmic (#5193)

* Kernel/Process: Notify the CPUs that a new pagetable has been set every time the process they're executing changes.

Previously the page table would only be changed when the current CPU's page table was changed, this lead to stale JIT states and the PC going to 0 when context-switching a different core inside the ThreadManager::SwitchContext function because the JIT for a new pagetable is only constructed upon receiving the change notification.

* Kernel/Process: Use the relevant CPU's last process to determine when to switch its current process.

Previously it was checking the kernel's current_process variable, which gets overwritten every time a CPU runs its slice. The rescheduling happens after all CPUs have run their slice so the code was effectively only checking the last CPU's process.

src/core/arm/arm_interface.h

@@ -11,6 +11,10 @@
 #include "core/arm/skyeye_common/vfp/asm_vfp.h"
 #include "core/core_timing.h"
 
+namespace Memory {
+struct PageTable;
+};
+
 /// Generic ARM11 CPU interface
 class ARM_Interface : NonCopyable {
 public:
@@ -73,7 +77,7 @@ public:
     virtual void InvalidateCacheRange(u32 start_address, std::size_t length) = 0;
 
     /// Notify CPU emulation that page tables have changed
-    virtual void PageTableChanged() = 0;
+    virtual void PageTableChanged(Memory::PageTable* new_page_table) = 0;
 
     /**
      * Set the Program Counter to an address

src/core/arm/dynarmic/arm_dynarmic.cpp

@@ -153,7 +153,7 @@ ARM_Dynarmic::ARM_Dynarmic(Core::System* system, Memory::MemorySystem& memory, u
                            std::shared_ptr<Core::Timing::Timer> timer)
     : ARM_Interface(id, timer), system(*system), memory(memory),
       cb(std::make_unique<DynarmicUserCallbacks>(*this)) {
-    PageTableChanged();
+    PageTableChanged(memory.GetCurrentPageTable());
 }
 
 ARM_Dynarmic::~ARM_Dynarmic() = default;
@@ -287,8 +287,8 @@ void ARM_Dynarmic::InvalidateCacheRange(u32 start_address, std::size_t length) {
     jit->InvalidateCacheRange(start_address, length);
 }
 
-void ARM_Dynarmic::PageTableChanged() {
-    current_page_table = memory.GetCurrentPageTable();
+void ARM_Dynarmic::PageTableChanged(Memory::PageTable* new_page_table) {
+    current_page_table = new_page_table;
 
     auto iter = jits.find(current_page_table);
     if (iter != jits.end()) {

src/core/arm/dynarmic/arm_dynarmic.h

@@ -52,7 +52,7 @@ public:
 
     void ClearInstructionCache() override;
     void InvalidateCacheRange(u32 start_address, std::size_t length) override;
-    void PageTableChanged() override;
+    void PageTableChanged(Memory::PageTable* new_page_table) override;
 
 private:
     void ServeBreak();

src/core/arm/dyncom/arm_dyncom.cpp

@@ -95,7 +95,7 @@ void ARM_DynCom::InvalidateCacheRange(u32, std::size_t) {
     ClearInstructionCache();
 }
 
-void ARM_DynCom::PageTableChanged() {
+void ARM_DynCom::PageTableChanged(Memory::PageTable*) {
     ClearInstructionCache();
 }
 

src/core/arm/dyncom/arm_dyncom.h

@@ -30,7 +30,7 @@ public:
 
     void ClearInstructionCache() override;
     void InvalidateCacheRange(u32 start_address, std::size_t length) override;
-    void PageTableChanged() override;
+    void PageTableChanged(Memory::PageTable* new_page_table) override;
 
     void SetPC(u32 pc) override;
     u32 GetPC() const override;

src/core/hle/kernel/kernel.cpp

@@ -67,13 +67,15 @@ void KernelSystem::SetCurrentProcessForCPU(std::shared_ptr<Process> process, u32
         SetCurrentMemoryPageTable(&process->vm_manager.page_table);
     } else {
         stored_processes[core_id] = process;
+        thread_managers[core_id]->cpu->PageTableChanged(&process->vm_manager.page_table);
     }
 }
 
 void KernelSystem::SetCurrentMemoryPageTable(Memory::PageTable* page_table) {
     memory.SetCurrentPageTable(page_table);
     if (current_cpu != nullptr) {
-        current_cpu->PageTableChanged(); // notify the CPU the page table in memory has changed
+        // Notify the CPU the page table in memory has changed
+        current_cpu->PageTableChanged(page_table);
     }
 }
 

src/core/hle/kernel/thread.cpp

@@ -75,11 +75,13 @@ void Thread::Stop() {
 
 void ThreadManager::SwitchContext(Thread* new_thread) {
     Thread* previous_thread = GetCurrentThread();
+    Process* previous_process = nullptr;
 
     Core::Timing& timing = kernel.timing;
 
     // Save context for previous thread
     if (previous_thread) {
+        previous_process = previous_thread->owner_process;
         previous_thread->last_running_ticks = timing.GetGlobalTicks();
         cpu->SaveContext(previous_thread->context);
 
@@ -99,14 +101,12 @@ void ThreadManager::SwitchContext(Thread* new_thread) {
         // Cancel any outstanding wakeup events for this thread
         timing.UnscheduleEvent(ThreadWakeupEventType, new_thread->thread_id);
 
-        auto previous_process = kernel.GetCurrentProcess();
-
         current_thread = SharedFrom(new_thread);
 
         ready_queue.remove(new_thread->current_priority, new_thread);
         new_thread->status = ThreadStatus::Running;
 
-        if (previous_process.get() != current_thread->owner_process) {
+        if (previous_process != current_thread->owner_process) {
             kernel.SetCurrentProcessForCPU(SharedFrom(current_thread->owner_process), cpu->GetID());
         }