Kernel: Fix sse state saving

This was broken when I added SMP support. This patch makes sse kind of
dumb as it is saved and restored on every interrupt, but now it at least
works properly... I'll have to look into how sse can get optimized
nicely with SMP. Simple way would be pinning each thread to a specific
processor and doing pretty much what I had before, but sse thread saved
in processor rather than static global.

.vscode/c_cpp_properties.json

@@ -8,7 +8,8 @@
                 "${workspaceFolder}/userspace/libraries/*/include"
             ],
             "defines": [
-				"__arch=x86_64"
+                "__arch=x86_64",
+                "__enable_sse=1"
             ],
             "compilerPath": "${workspaceFolder}/toolchain/local/bin/x86_64-banan_os-gcc",
             "cStandard": "c17",
@@ -24,7 +25,8 @@
             ],
             "defines": [
                 "__arch=x86_64",
-				"__is_kernel"
+                "__is_kernel",
+                "__enable_sse=1"
             ],
             "compilerPath": "${workspaceFolder}/toolchain/local/bin/x86_64-banan_os-gcc",
             "cStandard": "c17",

kernel/include/kernel/Thread.h

@@ -82,7 +82,6 @@ namespace Kernel
 #if __enable_sse
 		void save_sse();
 		void load_sse();
-		static Thread* sse_thread();
 #endif
 
 		void add_mutex() { m_mutex_count++; }

kernel/kernel/IDT.cpp

@@ -173,6 +173,10 @@ namespace Kernel
 
 		if (tid)
 		{
+#if __enable_sse
+			Thread::current().save_sse();
+#endif
+
 			if (isr == ISR::PageFault)
 			{
 				// Check if stack is OOB
@@ -218,31 +222,6 @@ namespace Kernel
 					}
 				}
 			}
-#if __enable_sse
-			else if (isr == ISR::DeviceNotAvailable)
-			{
-#if ARCH(x86_64)
-				asm volatile(
-					"movq %cr0, %rax;"
-					"andq $~(1 << 3), %rax;"
-					"movq %rax, %cr0;"
-				);
-#elif ARCH(i686)
-				asm volatile(
-					"movl %cr0, %eax;"
-					"andl $~(1 << 3), %eax;"
-					"movl %eax, %cr0;"
-				);
-#endif
-				if (auto* current = &Thread::current(); current != Thread::sse_thread())
-				{
-					if (auto* sse = Thread::sse_thread())
-						sse->save_sse();
-					current->load_sse();
-				}
-				goto done;
-			}
-#endif
 		}
 
 		Debug::s_debug_lock.lock();
@@ -334,7 +313,11 @@ namespace Kernel
 		ASSERT(Thread::current().state() != Thread::State::Terminated);
 
 done:
+#if __enable_sse
+		Thread::current().load_sse();
+#else
 		return;
+#endif
 	}
 
 	extern "C" void cpp_yield_handler(InterruptStack* interrupt_stack, InterruptRegisters* interrupt_registers)
@@ -357,6 +340,10 @@ done:
 			asm volatile("cli; 1: hlt; jmp 1b");
 		}
 
+#if __enable_sse
+		Thread::current().save_sse();
+#endif
+
 		if (!InterruptController::get().is_in_service(irq))
 			dprintln("spurious irq 0x{2H}", irq);
 		else
@@ -377,6 +364,10 @@ done:
 		Scheduler::get().reschedule_if_idling();
 
 		ASSERT(Thread::current().state() != Thread::State::Terminated);
+
+#if __enable_sse
+		Thread::current().load_sse();
+#endif
 	}
 
 	void IDT::register_interrupt_handler(uint8_t index, void (*handler)())

kernel/kernel/Thread.cpp

@@ -113,33 +113,8 @@ namespace Kernel
 		: m_tid(tid), m_process(process)
 	{
 #if __enable_sse
-	#if ARCH(x86_64)
+		// initializes sse storage to valid state
-		uintptr_t cr0;
-		asm volatile(
-			"movq %%cr0, %%rax;"
-			"movq %%rax, %[cr0];"
-			"andq $~(1 << 3), %%rax;"
-			"movq %%rax, %%cr0;"
-			: [cr0]"=r"(cr0)
-			:: "rax"
-		);
 		save_sse();
-		asm volatile("movq %0, %%cr0" :: "r"(cr0));
-	#elif ARCH(i686)
-		uintptr_t cr0;
-		asm volatile(
-			"movl %%cr0, %%eax;"
-			"movl %%eax, %[cr0];"
-			"andl $~(1 << 3), %%eax;"
-			"movl %%eax, %%cr0;"
-			: [cr0]"=r"(cr0)
-			:: "eax"
-		);
-		save_sse();
-		asm volatile("movl %0, %%cr0" :: "r"(cr0));
-	#else
-		#error
-	#endif
 #endif
 	}
 
@@ -482,8 +457,6 @@ namespace Kernel
 	}
 
 #if __enable_sse
-	static Thread* s_sse_thread = nullptr;
-
 	void Thread::save_sse()
 	{
 		asm volatile("fxsave %0" :: "m"(m_sse_storage));
@@ -492,12 +465,6 @@ namespace Kernel
 	void Thread::load_sse()
 	{
 		asm volatile("fxrstor %0" :: "m"(m_sse_storage));
-		s_sse_thread = this;
-	}
-
-	Thread* Thread::sse_thread()
-	{
-		return s_sse_thread;
 	}
 #endif