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

@@ -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);
+}

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;