Kernel: Minor MM optimization for SMP

MemoryManager::quickmap_pd and MemoryManager::quickmap_pt can only
be called by one processor at the time anyway, since anything using
these must have the MM lock held. So, no need to inform the other
CPUs to flush their TLBs, we can just flush our own.

2 files changed, 18 insertions, 12 deletions

diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index a01c611541..eac9f71994 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -60,6 +60,7 @@ MemoryManager& MM
 
 MemoryManager::MemoryManager()
 {
+    ScopedSpinLock lock(s_mm_lock);
     m_kernel_page_directory = PageDirectory::create_kernel_page_directory();
     parse_memory_map();
     write_cr3(kernel_page_directory().cr3());
@@ -165,7 +166,7 @@ void MemoryManager::parse_memory_map()
 const PageTableEntry* MemoryManager::pte(const PageDirectory& page_directory, VirtualAddress vaddr)
 {
     ASSERT_INTERRUPTS_DISABLED();
-    ScopedSpinLock lock(s_mm_lock);
+    ASSERT(s_mm_lock.own_lock());
     u32 page_directory_table_index = (vaddr.get() >> 30) & 0x3;
     u32 page_directory_index = (vaddr.get() >> 21) & 0x1ff;
     u32 page_table_index = (vaddr.get() >> 12) & 0x1ff;
@@ -181,7 +182,7 @@ const PageTableEntry* MemoryManager::pte(const PageDirectory& page_directory, Vi
 PageTableEntry& MemoryManager::ensure_pte(PageDirectory& page_directory, VirtualAddress vaddr)
 {
     ASSERT_INTERRUPTS_DISABLED();
-    ScopedSpinLock lock(s_mm_lock);
+    ASSERT(s_mm_lock.own_lock());
     u32 page_directory_table_index = (vaddr.get() >> 30) & 0x3;
     u32 page_directory_index = (vaddr.get() >> 21) & 0x1ff;
     u32 page_table_index = (vaddr.get() >> 12) & 0x1ff;
@@ -554,7 +555,7 @@ extern "C" PageTableEntry boot_pd3_pt1023[1024];
 
 PageDirectoryEntry* MemoryManager::quickmap_pd(PageDirectory& directory, size_t pdpt_index)
 {
-    ScopedSpinLock lock(s_mm_lock);
+    ASSERT(s_mm_lock.own_lock());
     auto& pte = boot_pd3_pt1023[4];
     auto pd_paddr = directory.m_directory_pages[pdpt_index]->paddr();
     if (pte.physical_page_base() != pd_paddr.as_ptr()) {
@@ -565,14 +566,17 @@ PageDirectoryEntry* MemoryManager::quickmap_pd(PageDirectory& directory, size_t
         pte.set_present(true);
         pte.set_writable(true);
         pte.set_user_allowed(false);
-        flush_tlb(VirtualAddress(0xffe04000));
+        // Because we must continue to hold the MM lock while we use this
+        // mapping, it is sufficient to only flush on the current CPU. Other
+        // CPUs trying to use this API must wait on the MM lock anyway
+        flush_tlb_local(VirtualAddress(0xffe04000));
     }
     return (PageDirectoryEntry*)0xffe04000;
 }
 
 PageTableEntry* MemoryManager::quickmap_pt(PhysicalAddress pt_paddr)
 {
-    ScopedSpinLock lock(s_mm_lock);
+    ASSERT(s_mm_lock.own_lock());
     auto& pte = boot_pd3_pt1023[0];
     if (pte.physical_page_base() != pt_paddr.as_ptr()) {
 #ifdef MM_DEBUG
@@ -582,7 +586,10 @@ PageTableEntry* MemoryManager::quickmap_pt(PhysicalAddress pt_paddr)
         pte.set_present(true);
         pte.set_writable(true);
         pte.set_user_allowed(false);
-        flush_tlb(VirtualAddress(0xffe00000));
+        // Because we must continue to hold the MM lock while we use this
+        // mapping, it is sufficient to only flush on the current CPU. Other
+        // CPUs trying to use this API must wait on the MM lock anyway
+        flush_tlb_local(VirtualAddress(0xffe00000));
     }
     return (PageTableEntry*)0xffe00000;
 }
@@ -606,7 +613,7 @@ u8* MemoryManager::quickmap_page(PhysicalPage& physical_page)
         pte.set_present(true);
         pte.set_writable(true);
         pte.set_user_allowed(false);
-        flush_tlb_local(vaddr, 1);
+        flush_tlb_local(vaddr);
     }
     return vaddr.as_ptr();
 }
@@ -621,7 +628,7 @@ void MemoryManager::unquickmap_page()
     VirtualAddress vaddr(0xffe00000 + pte_idx * PAGE_SIZE);
     auto& pte = boot_pd3_pt1023[pte_idx];
     pte.clear();
-    flush_tlb_local(vaddr, 1);
+    flush_tlb_local(vaddr);
     mm_data.m_quickmap_in_use.unlock(mm_data.m_quickmap_prev_flags);
 }
 
diff --git a/Kernel/VM/PageDirectory.cpp b/Kernel/VM/PageDirectory.cpp
index e04778dae9..b04febad88 100644
--- a/Kernel/VM/PageDirectory.cpp
+++ b/Kernel/VM/PageDirectory.cpp
@@ -48,7 +48,7 @@ static HashMap<u32, PageDirectory*>& cr3_map()
 
 RefPtr<PageDirectory> PageDirectory::find_by_cr3(u32 cr3)
 {
-    InterruptDisabler disabler;
+    ScopedSpinLock lock(s_mm_lock);
     return cr3_map().get(cr3).value_or({});
 }
 
@@ -76,6 +76,7 @@ PageDirectory::PageDirectory()
 PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_range_allocator)
     : m_process(&process)
 {
+    ScopedSpinLock lock(s_mm_lock);
     if (parent_range_allocator) {
         m_range_allocator.initialize_from_parent(*parent_range_allocator);
     } else {
@@ -93,7 +94,6 @@ PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_rang
     m_directory_pages[3] = MM.kernel_page_directory().m_directory_pages[3];
 
     {
-        InterruptDisabler disabler;
         auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*m_directory_table);
         table.raw[0] = (u64)m_directory_pages[0]->paddr().as_ptr() | 1;
         table.raw[1] = (u64)m_directory_pages[1]->paddr().as_ptr() | 1;
@@ -109,7 +109,6 @@ PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_rang
     auto* new_pd = MM.quickmap_pd(*this, 0);
     memcpy(new_pd, &buffer, sizeof(PageDirectoryEntry));
 
-    InterruptDisabler disabler;
     cr3_map().set(cr3(), this);
 }
 
@@ -118,7 +117,7 @@ PageDirectory::~PageDirectory()
 #ifdef MM_DEBUG
     dbg() << "MM: ~PageDirectory K" << this;
 #endif
-    InterruptDisabler disabler;
+    ScopedSpinLock lock(s_mm_lock);
     cr3_map().remove(cr3());
 }