From 13aa3d2d62e3fcd21c029cf91c930d09deb148cb Mon Sep 17 00:00:00 2001
From: Tom <tomut@yahoo.com>
Date: Sat, 31 Oct 2020 17:19:50 -0600
Subject: Kernel: Flush TLB when quick-mapping PD/PT that was mapped on other
 CPU

If a PD/PT was quick-mapped by another CPU we still need to flush the
TLB on the current CPU.

Fixes #3885
---
 Kernel/VM/MemoryManager.cpp | 16 ++++++++++++++++
 Kernel/VM/MemoryManager.h   |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index 9cebe27a20..fca0b8589a 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -648,6 +648,7 @@ extern "C" PageTableEntry boot_pd3_pt1023[1024];
 PageDirectoryEntry* MemoryManager::quickmap_pd(PageDirectory& directory, size_t pdpt_index)
 {
     ASSERT(s_mm_lock.own_lock());
+    auto& mm_data = get_data();
     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()) {
@@ -662,13 +663,21 @@ PageDirectoryEntry* MemoryManager::quickmap_pd(PageDirectory& directory, size_t
         // 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));
+    } else {
+        // Even though we don't allow this to be called concurrently, it's
+        // possible that this PD was mapped on a different CPU and we don't
+        // broadcast the flush. If so, we still need to flush the TLB.
+        if (mm_data.m_last_quickmap_pd != pd_paddr)
+            flush_tlb_local(VirtualAddress(0xffe04000));
     }
+    mm_data.m_last_quickmap_pd = pd_paddr;
     return (PageDirectoryEntry*)0xffe04000;
 }
 
 PageTableEntry* MemoryManager::quickmap_pt(PhysicalAddress pt_paddr)
 {
     ASSERT(s_mm_lock.own_lock());
+    auto& mm_data = get_data();
     auto& pte = boot_pd3_pt1023[0];
     if (pte.physical_page_base() != pt_paddr.as_ptr()) {
 #ifdef MM_DEBUG
@@ -682,7 +691,14 @@ PageTableEntry* MemoryManager::quickmap_pt(PhysicalAddress pt_paddr)
         // 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));
+    } else {
+        // Even though we don't allow this to be called concurrently, it's
+        // possible that this PT was mapped on a different CPU and we don't
+        // broadcast the flush. If so, we still need to flush the TLB.
+        if (mm_data.m_last_quickmap_pt != pt_paddr)
+            flush_tlb_local(VirtualAddress(0xffe00000));
     }
+    mm_data.m_last_quickmap_pt = pt_paddr;
     return (PageTableEntry*)0xffe00000;
 }
 
diff --git a/Kernel/VM/MemoryManager.h b/Kernel/VM/MemoryManager.h
index 2bf767a766..24c6fedf70 100644
--- a/Kernel/VM/MemoryManager.h
+++ b/Kernel/VM/MemoryManager.h
@@ -70,6 +70,9 @@ class SynthFSInode;
 struct MemoryManagerData {
     SpinLock<u8> m_quickmap_in_use;
     u32 m_quickmap_prev_flags;
+
+    PhysicalAddress m_last_quickmap_pd;
+    PhysicalAddress m_last_quickmap_pt;
 };
 
 extern RecursiveSpinLock s_mm_lock;
-- 
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