From 7704e3c5c0c22c285e65341720cf64b29a61f9dc Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Wed, 20 May 2026 00:16:56 +0300
Subject: [PATCH] Kernel: Implement per cpu fast pages

Basically every fast page usage should be converted into this but I'll
do them one by one when they show up in profiles
---
 kernel/arch/i686/PageTable.cpp           | 12 ++++++++++--
 kernel/arch/x86_64/PageTable.cpp         | 12 ++++++++++--
 kernel/include/kernel/Memory/PageTable.h | 20 ++++++++++++++++++++
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/kernel/arch/i686/PageTable.cpp b/kernel/arch/i686/PageTable.cpp
index 90013052..4ef9ce02 100644
--- a/kernel/arch/i686/PageTable.cpp
+++ b/kernel/arch/i686/PageTable.cpp
@@ -258,7 +258,11 @@ namespace Kernel
 
 		ASSERT(index < 512);
 		ASSERT(s_fast_page_pt);
-		ASSERT(s_fast_page_lock.current_processor_has_lock());
+
+		if (index < reserved_fast_pages)
+			ASSERT(s_fast_page_lock.current_processor_has_lock());
+		else
+			ASSERT(Processor::get_interrupt_state() == InterruptState::Disabled);
 
 		ASSERT(!(s_fast_page_pt[index] & Flags::Present));
 		s_fast_page_pt[index] = paddr | Flags::ReadWrite | Flags::Present;
@@ -272,7 +276,11 @@ namespace Kernel
 	{
 		ASSERT(index < 512);
 		ASSERT(s_fast_page_pt);
-		ASSERT(s_fast_page_lock.current_processor_has_lock());
+
+		if (index < reserved_fast_pages)
+			ASSERT(s_fast_page_lock.current_processor_has_lock());
+		else
+			ASSERT(Processor::get_interrupt_state() == InterruptState::Disabled);
 
 		ASSERT((s_fast_page_pt[index] & Flags::Present));
 		s_fast_page_pt[index] = 0;
diff --git a/kernel/arch/x86_64/PageTable.cpp b/kernel/arch/x86_64/PageTable.cpp
index fa57f1c8..dd410d23 100644
--- a/kernel/arch/x86_64/PageTable.cpp
+++ b/kernel/arch/x86_64/PageTable.cpp
@@ -382,7 +382,11 @@ namespace Kernel
 
 		ASSERT(index < 512);
 		ASSERT(s_fast_page_pt);
-		ASSERT(s_fast_page_lock.current_processor_has_lock());
+
+		if (index < reserved_fast_pages)
+			ASSERT(s_fast_page_lock.current_processor_has_lock());
+		else
+			ASSERT(Processor::get_interrupt_state() == InterruptState::Disabled);
 
 		ASSERT(!(s_fast_page_pt[index] & Flags::Present));
 		s_fast_page_pt[index] = paddr | Flags::ReadWrite | Flags::Present;
@@ -396,7 +400,11 @@ namespace Kernel
 	{
 		ASSERT(index < 512);
 		ASSERT(s_fast_page_pt);
-		ASSERT(s_fast_page_lock.current_processor_has_lock());
+
+		if (index < reserved_fast_pages)
+			ASSERT(s_fast_page_lock.current_processor_has_lock());
+		else
+			ASSERT(Processor::get_interrupt_state() == InterruptState::Disabled);
 
 		ASSERT((s_fast_page_pt[index] & Flags::Present));
 		s_fast_page_pt[index] = 0;
diff --git a/kernel/include/kernel/Memory/PageTable.h b/kernel/include/kernel/Memory/PageTable.h
index 146c8985..68930860 100644
--- a/kernel/include/kernel/Memory/PageTable.h
+++ b/kernel/include/kernel/Memory/PageTable.h
@@ -14,6 +14,12 @@ namespace Kernel
 		requires BAN::is_same_v<decltype(func()), void>;
 	};
 
+	template<typename F>
+	concept with_per_cpu_fast_page_callback = requires(F func, void* addr)
+	{
+		requires BAN::is_same_v<decltype(func(addr)), void>;
+	};
+
 	template<typename F>
 	concept with_fast_page_callback_error = requires(F func)
 	{
@@ -47,6 +53,8 @@ namespace Kernel
 
 		static constexpr bool full_tlb_flush_threshold = 32;
 
+		static constexpr size_t reserved_fast_pages = 0x10;
+
 	public:
 		static void initialize_fast_page();
 		static void initialize_and_load();
@@ -74,6 +82,18 @@ namespace Kernel
 			unmap_fast_page();
 		}
 
+		template<with_per_cpu_fast_page_callback F>
+		static void with_per_cpu_fast_page(paddr_t paddr, F callback)
+		{
+			const auto state = Processor::get_interrupt_state();
+			Processor::set_interrupt_state(InterruptState::Disabled);
+			const size_t index = Processor::current_index() + reserved_fast_pages;
+			void* addr = map_fast_page(index, paddr);
+			callback(addr);
+			unmap_fast_page(index);
+			Processor::set_interrupt_state(state);
+		}
+
 		template<with_fast_page_callback_error F>
 		static BAN::ErrorOr<void> with_fast_page(paddr_t paddr, F callback)
 		{