From 33cb81b9d1a7e0c36e874e4d7cfb169cf6551add Mon Sep 17 00:00:00 2001
From: Stephen Miller <millerste004@gmail.com>
Date: Fri, 9 May 2025 20:41:55 -0500
Subject: [PATCH] Adjust fixed PoolReserve path

Hardware tests suggest this will overwrite all VMAs in the range. Run UnmapMemoryImpl on the full area, then reserve. Same logic applies to normal reservations too.

Also adjusts logic of the non-fixed path to more closely align with hardware observations.
---
 src/core/memory.cpp | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/src/core/memory.cpp b/src/core/memory.cpp
index cda66c30a..9746da533 100644
--- a/src/core/memory.cpp
+++ b/src/core/memory.cpp
@@ -218,23 +218,20 @@ int MemoryManager::PoolReserve(void** out_addr, VAddr virtual_addr, size_t size,
 
     // Fixed mapping means the virtual address must exactly match the provided one.
     if (True(flags & MemoryMapFlags::Fixed)) {
-        auto& vma = FindVMA(mapped_addr)->second;
-        // If the VMA is mapped, unmap the region first.
-        if (vma.IsMapped()) {
+        auto vma = FindVMA(mapped_addr)->second;
+        size_t remaining_size = vma.base + vma.size - mapped_addr;
+        // If the VMA is mapped or there's not enough space, unmap the region first.
+        if (vma.IsMapped() || remaining_size < size) {
             UnmapMemoryImpl(mapped_addr, size);
             vma = FindVMA(mapped_addr)->second;
+            remaining_size = vma.base + vma.size - mapped_addr;
         }
-        const size_t remaining_size = vma.base + vma.size - mapped_addr;
-        ASSERT_MSG(vma.type == VMAType::Free && remaining_size >= size,
-                   "Memory region {:#x} to {:#x} is not large enough to reserve {:#x} to {:#x}",
-                   vma.base, vma.base + vma.size, virtual_addr, virtual_addr + size);
     }
 
-    // Find the first free area starting with provided virtual address.
     if (False(flags & MemoryMapFlags::Fixed)) {
-        // When MemoryMapFlags::Fixed is not specified, mappings default to searching for
-        // a free area starting from address 0x200000000 instead.
-        mapped_addr = mapped_addr < 0x200000000 ? 0x200000000 : mapped_addr;
+        // When MemoryMapFlags::Fixed is not specified, and mapped_addr is 0,
+        // search from address 0x200000000 instead.
+        mapped_addr = mapped_addr == 0 ? 0x200000000 : mapped_addr;
         mapped_addr = SearchFree(mapped_addr, size, alignment);
         if (mapped_addr == -1) {
             // No suitable memory areas to map to
@@ -265,15 +262,13 @@ int MemoryManager::Reserve(void** out_addr, VAddr virtual_addr, size_t size, Mem
     // Fixed mapping means the virtual address must exactly match the provided one.
     if (True(flags & MemoryMapFlags::Fixed)) {
         auto vma = FindVMA(mapped_addr)->second;
-        // If the VMA is mapped, unmap the region first.
-        if (vma.IsMapped()) {
+        size_t remaining_size = vma.base + vma.size - mapped_addr;
+        // If the VMA is mapped or there's not enough space, unmap the region first.
+        if (vma.IsMapped() || remaining_size < size) {
             UnmapMemoryImpl(mapped_addr, size);
             vma = FindVMA(mapped_addr)->second;
+            remaining_size = vma.base + vma.size - mapped_addr;
         }
-        const size_t remaining_size = vma.base + vma.size - mapped_addr;
-        ASSERT_MSG(vma.type == VMAType::Free && remaining_size >= size,
-                   "Memory region {:#x} to {:#x} is not large enough to reserve {:#x} to {:#x}",
-                   vma.base, vma.base + vma.size, virtual_addr, virtual_addr + size);
     }
 
     // Find the first free area starting with provided virtual address.