From 609f34cc492ad670bcba59f11c3092a156b3d628 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Sun, 23 Mar 2025 15:36:05 +0100
Subject: [PATCH] Only flush write MMU cache on WP flag toggle as read and
 execute MMU cache is not affected by the flag.

---
 src/cpu/x86_ops_mov_ctrl.h      | 10 ++++++----
 src/cpu/x86_ops_mov_ctrl_2386.h | 10 ++++++----
 src/include/86box/mem.h         |  1 +
 src/mem/mem.c                   | 15 +++++++++++++++
 4 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/src/cpu/x86_ops_mov_ctrl.h b/src/cpu/x86_ops_mov_ctrl.h
index b4f0c498a..253dc059e 100644
--- a/src/cpu/x86_ops_mov_ctrl.h
+++ b/src/cpu/x86_ops_mov_ctrl.h
@@ -184,7 +184,7 @@ opMOV_CRx_r_a16(uint32_t fetchdat)
     fetch_ea_16(fetchdat);
     switch (cpu_reg) {
         case 0:
-            if ((cpu_state.regs[cpu_rm].l ^ cr0) & (0x00000001 | WP_FLAG))
+            if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x00000001)
                 flushmmucache();
             else if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x80000000) {
                 if (is_p6 || cpu_use_dynarec)
@@ -193,7 +193,8 @@ opMOV_CRx_r_a16(uint32_t fetchdat)
                     flushmmucache_nopc();
                     cpu_flush_pending = 1;
                 }
-            }
+            } else if ((cpu_state.regs[cpu_rm].l ^ cr0) & WP_FLAG)
+                flushmmucache_write();
             /* Make sure CPL = 0 when switching from real mode to protected mode. */
             if ((cpu_state.regs[cpu_rm].l & 0x01) && !(cr0 & 0x01))
                 cpu_state.seg_cs.access &= 0x9f;
@@ -249,7 +250,7 @@ opMOV_CRx_r_a32(uint32_t fetchdat)
     fetch_ea_32(fetchdat);
     switch (cpu_reg) {
         case 0:
-            if ((cpu_state.regs[cpu_rm].l ^ cr0) & (0x00000001 | WP_FLAG))
+            if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x00000001)
                 flushmmucache();
             else if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x80000000) {
                 if (is_p6 || cpu_use_dynarec)
@@ -258,7 +259,8 @@ opMOV_CRx_r_a32(uint32_t fetchdat)
                     flushmmucache_nopc();
                     cpu_flush_pending = 1;
                 }
-            }
+            } else if ((cpu_state.regs[cpu_rm].l ^ cr0) & WP_FLAG)
+                flushmmucache_write();
             /* Make sure CPL = 0 when switching from real mode to protected mode. */
             if ((cpu_state.regs[cpu_rm].l & 0x01) && !(cr0 & 0x01))
                 cpu_state.seg_cs.access &= 0x9f;
diff --git a/src/cpu/x86_ops_mov_ctrl_2386.h b/src/cpu/x86_ops_mov_ctrl_2386.h
index 13e08a145..8827d29b2 100644
--- a/src/cpu/x86_ops_mov_ctrl_2386.h
+++ b/src/cpu/x86_ops_mov_ctrl_2386.h
@@ -180,12 +180,13 @@ opMOV_CRx_r_a16(uint32_t fetchdat)
     fetch_ea_16(fetchdat);
     switch (cpu_reg) {
         case 0:
-            if ((cpu_state.regs[cpu_rm].l ^ cr0) & (0x00000001 | WP_FLAG))
+            if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x00000001)
                 flushmmucache();
             else if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x80000000) {
                 flushmmucache_nopc();
                 cpu_flush_pending = 1;
-            }
+            } else if ((cpu_state.regs[cpu_rm].l ^ cr0) & WP_FLAG)
+                flushmmucache_write();
             /* Make sure CPL = 0 when switching from real mode to protected mode. */
             if ((cpu_state.regs[cpu_rm].l & 0x01) && !(cr0 & 0x01))
                 cpu_state.seg_cs.access &= 0x9f;
@@ -241,12 +242,13 @@ opMOV_CRx_r_a32(uint32_t fetchdat)
     fetch_ea_32(fetchdat);
     switch (cpu_reg) {
         case 0:
-            if ((cpu_state.regs[cpu_rm].l ^ cr0) & (0x00000001 | WP_FLAG))
+            if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x00000001)
                 flushmmucache();
             else if ((cpu_state.regs[cpu_rm].l ^ cr0) & 0x80000000) {
                 flushmmucache_nopc();
                 cpu_flush_pending = 1;
-            }
+            } else if ((cpu_state.regs[cpu_rm].l ^ cr0) & WP_FLAG)
+                flushmmucache_write();
             /* Make sure CPL = 0 when switching from real mode to protected mode. */
             if ((cpu_state.regs[cpu_rm].l & 0x01) && !(cr0 & 0x01))
                 cpu_state.seg_cs.access &= 0x9f;
diff --git a/src/include/86box/mem.h b/src/include/86box/mem.h
index 19a331925..81b46b2fa 100644
--- a/src/include/86box/mem.h
+++ b/src/include/86box/mem.h
@@ -448,6 +448,7 @@ extern void mem_flush_write_page(uint32_t addr, uint32_t virt);
 extern void mem_reset_page_blocks(void);
 
 extern void flushmmucache(void);
+extern void flushmmucache_write(void);
 extern void flushmmucache_pc(void);
 extern void flushmmucache_nopc(void);
 
diff --git a/src/mem/mem.c b/src/mem/mem.c
index d85b20581..94c4ab788 100644
--- a/src/mem/mem.c
+++ b/src/mem/mem.c
@@ -225,6 +225,21 @@ flushmmucache(void)
 #endif
 }
 
+void
+flushmmucache_write(void)
+{
+    for (uint16_t c = 0; c < 256; c++) {
+        if (writelookup[c] != (int) 0xffffffff) {
+            page_lookup[writelookup[c]]  = NULL;
+            page_lookupp[writelookup[c]] = 4;
+            writelookup2[writelookup[c]] = LOOKUP_INV;
+            writelookupp[writelookup[c]] = 4;
+            writelookup[c]               = 0xffffffff;
+        }
+    }
+    mmuflush++;
+}
+
 void
 flushmmucache_pc(void)
 {