From 5e026edfdc112f675536effe62347a73062a3cb4 Mon Sep 17 00:00:00 2001
From: Stefan Ginsberg <stefanginsberg@gmail.com>
Date: Wed, 14 Oct 2015 19:33:35 +0000
Subject: [PATCH] [NTOS] Add super-complicated handling of global pages to
 KeFlushCurrentTb (pretty much the same code which has been in HalpFlushTLB
 for the past ~6 years). This should be all that is required to make this
 feature work (everything else being in place already), and *seems* to work
 fine but is disabled under a switch until tested thoroughly.

Global pages, an important optimization that allows for not flushing the whole x86 TLB every time CR3 is changed (typically on context switch to a new process, or during process attach/detach), relies on us doing extra work whenever we do alter a global page. This is likely where any bugs will have to be flushed out!

Fixup Ki386EnableGlobalPage while we are at it -- disable/restore interrupts properly, and verify PGE-bit isn't set (nothing should have touched it before this routine, which is responsible for initializing it, so we shouldn't have to disable it). Fix, but disable, the CPU-sync spin as well as there should be no particular reason to do this for PGE-enabling during initialization (no other processor will be messing with PTEs at this stage, as compared to a call to KeFlushEntireTb).

Everyone, repeat after me: Global pages are awesome!

svn path=/trunk/; revision=69528
---
 reactos/ntoskrnl/include/ntoskrnl.h  |  8 ++++++
 reactos/ntoskrnl/ke/i386/cpu.c       | 29 ++++++++++++++++++++
 reactos/ntoskrnl/ke/i386/patpge.c    | 41 ++++++++++++++--------------
 reactos/ntoskrnl/mm/ARM3/i386/init.c |  5 +++-
 4 files changed, 62 insertions(+), 21 deletions(-)

diff --git a/reactos/ntoskrnl/include/ntoskrnl.h b/reactos/ntoskrnl/include/ntoskrnl.h
index 404878ad00d..400a153ccc9 100644
--- a/reactos/ntoskrnl/include/ntoskrnl.h
+++ b/reactos/ntoskrnl/include/ntoskrnl.h
@@ -98,6 +98,14 @@
 #define ASSERT NT_ASSERT
 #endif
 
+
+//
+// Switch for enabling global page support
+//
+
+//#define _GLOBAL_PAGES_ARE_AWESOME_
+
+
 /* Internal Headers */
 #include "internal/ntoskrnl.h"
 #include "config.h"
diff --git a/reactos/ntoskrnl/ke/i386/cpu.c b/reactos/ntoskrnl/ke/i386/cpu.c
index c9ca0cda244..3d4ea82d9b8 100644
--- a/reactos/ntoskrnl/ke/i386/cpu.c
+++ b/reactos/ntoskrnl/ke/i386/cpu.c
@@ -878,8 +878,37 @@ VOID
 NTAPI
 KeFlushCurrentTb(VOID)
 {
+
+#if !defined(_GLOBAL_PAGES_ARE_AWESOME_)
+
     /* Flush the TLB by resetting CR3 */
     __writecr3(__readcr3());
+
+#else
+
+    /* Check if global pages are enabled */
+    if (KeFeatureBits & KF_GLOBAL_PAGE)
+    {
+        ULONG Cr4;
+
+        /* Disable PGE */
+        Cr4 = __readcr4() & ~CR4_PGE;
+        __writecr4(Cr4);
+
+        /* Flush everything */
+        __writecr3(__readcr3());
+
+        /* Re-enable PGE */
+        __writecr4(Cr4 | CR4_PGE);
+    }
+    else
+    {
+        /* No global pages, resetting CR3 is enough */
+        __writecr3(__readcr3());
+    }
+
+#endif
+
 }
 
 VOID
diff --git a/reactos/ntoskrnl/ke/i386/patpge.c b/reactos/ntoskrnl/ke/i386/patpge.c
index 1e598ce355a..a0e9b494240 100644
--- a/reactos/ntoskrnl/ke/i386/patpge.c
+++ b/reactos/ntoskrnl/ke/i386/patpge.c
@@ -17,40 +17,41 @@
 
 /* FUNCTIONS *****************************************************************/
 
+INIT_SECTION
 ULONG_PTR
 NTAPI
-INIT_FUNCTION
 Ki386EnableGlobalPage(IN ULONG_PTR Context)
 {
-    PLONG Count = (PLONG)Context;
-    ULONG Cr4, Cr3;
+    //PLONG Count;
+#if defined(_GLOBAL_PAGES_ARE_AWESOME_)
+    ULONG Cr4;
+#endif
+    BOOLEAN Enable;
 
     /* Disable interrupts */
-    _disable();
+    Enable = KeDisableInterrupts();
 
-    /* Decrease CPU Count and loop until it's reached 0 */
-    do {InterlockedDecrement(Count);} while (!*Count);
+    /* Spin until other processors are ready */
+    //Count = (PLONG)Context;
+    //InterlockedDecrement(Count);
+    //while (*Count) YieldProcessor();
 
-    /* Now check if this is the Boot CPU */
-    if (!KeGetPcr()->Number)
-    {
-        /* It is.FIXME: Patch KeFlushCurrentTb */
-    }
+#if defined(_GLOBAL_PAGES_ARE_AWESOME_)
 
-    /* Now get CR4 and make sure PGE is masked out */
+    /* Get CR4 and ensure global pages are disabled */
     Cr4 = __readcr4();
-    __writecr4(Cr4 & ~CR4_PGE);
+    ASSERT(!(Cr4 & CR4_PGE));
 
-    /* Flush the TLB */
-    Cr3 = __readcr3();
-    __writecr3(Cr3);
+    /* Reset CR3 to flush the TLB */
+    __writecr3(__readcr3());
 
     /* Now enable PGE */
-    DPRINT("Global page support detected but not yet taken advantage of\n");
-    //__writecr4(Cr4 | CR4_PGE);
+    __writecr4(Cr4 | CR4_PGE);
 
-    /* Restore interrupts */
-    _enable();
+#endif
+
+    /* Restore interrupts and return */
+    KeRestoreInterrupts(Enable);
     return 0;
 }
 
diff --git a/reactos/ntoskrnl/mm/ARM3/i386/init.c b/reactos/ntoskrnl/mm/ARM3/i386/init.c
index c5c6bb308ba..5a42219302d 100644
--- a/reactos/ntoskrnl/mm/ARM3/i386/init.c
+++ b/reactos/ntoskrnl/mm/ARM3/i386/init.c
@@ -249,15 +249,18 @@ MiInitMachineDependent(IN PLOADER_PARAMETER_BLOCK LoaderBlock)
     PMMPFN Pfn1;
     ULONG Flags;
 
+#if defined(_GLOBAL_PAGES_ARE_AWESOME_)
+
     /* Check for global bit */
-#if 0
     if (KeFeatureBits & KF_GLOBAL_PAGE)
     {
         /* Set it on the template PTE and PDE */
         ValidKernelPte.u.Hard.Global = TRUE;
         ValidKernelPde.u.Hard.Global = TRUE;
     }
+
 #endif
+
     /* Now templates are ready */
     TempPte = ValidKernelPte;
     TempPde = ValidKernelPde;