Force all exclusive memory accesses to be ordered on AppleHv (#5898)

* Implement reprotect method on virtual memory manager (currently stubbed)

* Force all exclusive memory accesses to be ordered on AppleHv

* Format whitespace

* Fix test build

* Fix comment copy/paste

* Fix wrong bit for isLoad

* Update src/Ryujinx.Cpu/AppleHv/HvMemoryManager.cs

Co-authored-by: riperiperi <rhy3756547@hotmail.com>

---------

Co-authored-by: riperiperi <rhy3756547@hotmail.com>

2 files changed, 80 insertions, 15 deletions

diff --git a/src/Ryujinx.Cpu/AppleHv/HvCodePatcher.cs b/src/Ryujinx.Cpu/AppleHv/HvCodePatcher.cs
new file mode 100644
index 00000000..876597b7
--- /dev/null
+++ b/src/Ryujinx.Cpu/AppleHv/HvCodePatcher.cs
@@ -0,0 +1,62 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.Intrinsics;
+
+namespace Ryujinx.Cpu.AppleHv
+{
+    static class HvCodePatcher
+    {
+        private const uint XMask = 0x3f808000u;
+        private const uint XValue = 0x8000000u;
+
+        private const uint ZrIndex = 31u;
+
+        public static void RewriteUnorderedExclusiveInstructions(Span<byte> code)
+        {
+            Span<uint> codeUint = MemoryMarshal.Cast<byte, uint>(code);
+            Span<Vector128<uint>> codeVector = MemoryMarshal.Cast<byte, Vector128<uint>>(code);
+
+            Vector128<uint> mask = Vector128.Create(XMask);
+            Vector128<uint> value = Vector128.Create(XValue);
+
+            for (int index = 0; index < codeVector.Length; index++)
+            {
+                Vector128<uint> v = codeVector[index];
+
+                if (Vector128.EqualsAny(Vector128.BitwiseAnd(v, mask), value))
+                {
+                    int baseIndex = index * 4;
+
+                    for (int instIndex = baseIndex; instIndex < baseIndex + 4; instIndex++)
+                    {
+                        ref uint inst = ref codeUint[instIndex];
+
+                        if ((inst & XMask) != XValue)
+                        {
+                            continue;
+                        }
+
+                        bool isPair = (inst & (1u << 21)) != 0;
+                        bool isLoad = (inst & (1u << 22)) != 0;
+
+                        uint rt2 = (inst >> 10) & 0x1fu;
+                        uint rs = (inst >> 16) & 0x1fu;
+
+                        if (isLoad && rs != ZrIndex)
+                        {
+                            continue;
+                        }
+
+                        if (!isPair && rt2 != ZrIndex)
+                        {
+                            continue;
+                        }
+
+                        // Set the ordered flag.
+                        inst |= 1u << 15;
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/Ryujinx.Cpu/AppleHv/HvMemoryManager.cs b/src/Ryujinx.Cpu/AppleHv/HvMemoryManager.cs
index d5ce817a..947c3710 100644
--- a/src/Ryujinx.Cpu/AppleHv/HvMemoryManager.cs
+++ b/src/Ryujinx.Cpu/AppleHv/HvMemoryManager.cs
@@ -128,21 +128,6 @@ namespace Ryujinx.Cpu.AppleHv
             }
         }
 
-#pragma warning disable IDE0051 // Remove unused private member
-        /// <summary>
-        /// Ensures the combination of virtual address and size is part of the addressable space and fully mapped.
-        /// </summary>
-        /// <param name="va">Virtual address of the range</param>
-        /// <param name="size">Size of the range in bytes</param>
-        private void AssertMapped(ulong va, ulong size)
-        {
-            if (!ValidateAddressAndSize(va, size) || !IsRangeMappedImpl(va, size))
-            {
-                throw new InvalidMemoryRegionException($"Not mapped: va=0x{va:X16}, size=0x{size:X16}");
-            }
-        }
-#pragma warning restore IDE0051
-
         /// <inheritdoc/>
         public void Map(ulong va, ulong pa, ulong size, MemoryMapFlags flags)
         {
@@ -737,6 +722,24 @@ namespace Ryujinx.Cpu.AppleHv
         }
 
         /// <inheritdoc/>
+        public void Reprotect(ulong va, ulong size, MemoryPermission protection)
+        {
+            if (protection.HasFlag(MemoryPermission.Execute))
+            {
+                // Some applications use unordered exclusive memory access instructions
+                // where it is not valid to do so, leading to memory re-ordering that
+                // makes the code behave incorrectly on some CPUs.
+                // To work around this, we force all such accesses to be ordered.
+
+                using WritableRegion writableRegion = GetWritableRegion(va, (int)size);
+
+                HvCodePatcher.RewriteUnorderedExclusiveInstructions(writableRegion.Memory.Span);
+            }
+
+            // TODO
+        }
+
+        /// <inheritdoc/>
         public void TrackingReprotect(ulong va, ulong size, MemoryPermission protection)
         {
             // Protection is inverted on software pages, since the default value is 0.