From a5ffa2eec796c0e4a856cd718000e4657cd4b213 Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Mon, 31 Dec 2018 20:52:59 +0100
Subject: [PATCH] Add a PageDirectory::flush() that does nothing if another PD
 is active.

This way callers can just flush() every time after making any modification
and the PageDirectory itself will decide if TLB invalidation is necessary.
---
 Kernel/MemoryManager.cpp | 23 ++++++++++-------------
 Kernel/MemoryManager.h   |  2 +-
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/Kernel/MemoryManager.cpp b/Kernel/MemoryManager.cpp
index 283b5aaf7d..25f3cb6c70 100644
--- a/Kernel/MemoryManager.cpp
+++ b/Kernel/MemoryManager.cpp
@@ -439,8 +439,7 @@ void MemoryManager::remap_region_page(PageDirectory& page_directory, Region& reg
     else
         pte.set_writable(region.is_writable);
     pte.set_user_allowed(user_allowed);
-    if (page_directory.is_active())
-        flush_tlb(page_laddr);
+    page_directory.flush(page_laddr);
 #ifdef MM_DEBUG
     dbgprintf("MM: >> remap_region_page (PD=%x) '%s' L%x => P%x (@%p)\n", &page_directory, region.name.characters(), page_laddr.get(), physical_page->paddr().get(), physical_page.ptr());
 #endif
@@ -477,8 +476,7 @@ void MemoryManager::map_region_at_address(PageDirectory& page_directory, Region&
             pte.set_writable(region.is_writable);
         }
         pte.set_user_allowed(user_allowed);
-        if (page_directory.is_active())
-            flush_tlb(page_laddr);
+        page_directory.flush(page_laddr);
 #ifdef MM_DEBUG
         dbgprintf("MM: >> map_region_at_address (PD=%x) '%s' L%x => P%x (@%p)\n", &page_directory, region.name.characters(), page_laddr, physical_page ? physical_page->paddr().get() : 0, physical_page.ptr());
 #endif
@@ -498,8 +496,7 @@ void MemoryManager::unmap_range(PageDirectory& page_directory, LinearAddress lad
         pte.set_present(false);
         pte.set_writable(false);
         pte.set_user_allowed(false);
-        if (page_directory.is_active())
-            flush_tlb(page_laddr);
+        page_directory.flush(page_laddr);
 #ifdef MM_DEBUG
         dbgprintf("MM: << unmap_range L%x =/> 0\n", page_laddr);
 #endif
@@ -548,8 +545,7 @@ bool MemoryManager::unmap_region(Process& process, Region& region)
         pte.set_present(false);
         pte.set_writable(false);
         pte.set_user_allowed(false);
-        if (process.page_directory().is_active())
-            flush_tlb(laddr);
+        process.page_directory().flush(laddr);
 #ifdef MM_DEBUG
         auto& physical_page = region.vmo().physical_pages()[region.first_page_index() + i];
         dbgprintf("MM: >> Unmapped L%x => P%x <<\n", laddr, physical_page ? physical_page->paddr().get() : 0);
@@ -772,11 +768,6 @@ void MemoryManager::unregister_region(Region& region)
     m_regions.remove(&region);
 }
 
-inline bool PageDirectory::is_active() const
-{
-    return &current->page_directory() == this;
-}
-
 size_t Region::committed() const
 {
     size_t bytes = 0;
@@ -801,3 +792,9 @@ PageDirectory::~PageDirectory()
         MM.remove_identity_mapping(LinearAddress(page_table.paddr().get()), PAGE_SIZE);
     }
 }
+
+void PageDirectory::flush(LinearAddress laddr)
+{
+    if (&current->page_directory() == this)
+        MM.flush_tlb(laddr);
+}
diff --git a/Kernel/MemoryManager.h b/Kernel/MemoryManager.h
index 3c0a6f6408..1e29a2254a 100644
--- a/Kernel/MemoryManager.h
+++ b/Kernel/MemoryManager.h
@@ -61,7 +61,7 @@ public:
     dword cr3() const { return m_directory_page->paddr().get(); }
     dword* entries() { return reinterpret_cast<dword*>(cr3()); }
 
-    bool is_active() const;
+    void flush(LinearAddress);
 
 private:
     RetainPtr<PhysicalPage> m_directory_page;