6 files changed, 45 insertions, 13 deletions

diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index b1d76d6985..3771b2130c 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -67,7 +67,7 @@ typedef uintptr_t ram_addr_t;
 
 /* memory API */
 
-void qemu_ram_remap(ram_addr_t addr, ram_addr_t length);
+void qemu_ram_remap(ram_addr_t addr);
 /* This should not be used by devices.  */
 ram_addr_t qemu_ram_addr_from_host(void *ptr);
 ram_addr_t qemu_ram_addr_from_host_nofail(void *ptr);
diff --git a/include/exec/memattrs.h b/include/exec/memattrs.h
index 060b7e7131..8db1d30464 100644
--- a/include/exec/memattrs.h
+++ b/include/exec/memattrs.h
@@ -44,6 +44,8 @@ typedef struct MemTxAttrs {
      * (see MEMTX_ACCESS_ERROR).
      */
     unsigned int memory:1;
+    /* Debug access that can even write to ROM. */
+    unsigned int debug:1;
     /* Requester ID (for MSI for example) */
     unsigned int requester_id:16;
 
@@ -56,7 +58,8 @@ typedef struct MemTxAttrs {
      * Bus masters which don't specify any attributes will get this
      * (via the MEMTXATTRS_UNSPECIFIED constant), so that we can
      * distinguish "all attributes deliberately clear" from
-     * "didn't specify" if necessary.
+     * "didn't specify" if necessary. "debug" can be set alongside
+     * "unspecified".
      */
     bool unspecified;
 
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 9f73b59867..78c4e0aec8 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2995,15 +2995,34 @@ MemTxResult address_space_write_cached_slow(MemoryRegionCache *cache,
 int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr);
 bool prepare_mmio_access(MemoryRegion *mr);
 
-static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write)
+static inline bool memory_region_supports_direct_access(MemoryRegion *mr)
 {
-    if (is_write) {
-        return memory_region_is_ram(mr) && !mr->readonly &&
-               !mr->rom_device && !memory_region_is_ram_device(mr);
-    } else {
-        return (memory_region_is_ram(mr) && !memory_region_is_ram_device(mr)) ||
-               memory_region_is_romd(mr);
+    /* ROM DEVICE regions only allow direct access if in ROMD mode. */
+    if (memory_region_is_romd(mr)) {
+        return true;
+    }
+    if (!memory_region_is_ram(mr)) {
+        return false;
+    }
+    /*
+     * RAM DEVICE regions can be accessed directly using memcpy, but it might
+     * be MMIO and access using mempy can be wrong (e.g., using instructions not
+     * intended for MMIO access). So we treat this as IO.
+     */
+    return !memory_region_is_ram_device(mr);
+}
+
+static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write,
+                                           MemTxAttrs attrs)
+{
+    if (!memory_region_supports_direct_access(mr)) {
+        return false;
+    }
+    /* Debug access can write to ROM. */
+    if (is_write && !attrs.debug) {
+        return !mr->readonly && !mr->rom_device;
     }
+    return true;
 }
 
 /**
@@ -3036,7 +3055,7 @@ MemTxResult address_space_read(AddressSpace *as, hwaddr addr,
             fv = address_space_to_flatview(as);
             l = len;
             mr = flatview_translate(fv, addr, &addr1, &l, false, attrs);
-            if (len == l && memory_access_is_direct(mr, false)) {
+            if (len == l && memory_access_is_direct(mr, false, attrs)) {
                 ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
                 memcpy(buf, ptr, len);
             } else {
diff --git a/include/system/os-posix.h b/include/system/os-posix.h
index b881ac6c6f..ce5b3bccf8 100644
--- a/include/system/os-posix.h
+++ b/include/system/os-posix.h
@@ -53,7 +53,7 @@ bool os_set_runas(const char *user_id);
 void os_set_chroot(const char *path);
 void os_setup_limits(void);
 void os_setup_post(void);
-int os_mlock(void);
+int os_mlock(bool on_fault);
 
 /**
  * qemu_alloc_stack:
diff --git a/include/system/os-win32.h b/include/system/os-win32.h
index b82a5d3ad9..bc623061d8 100644
--- a/include/system/os-win32.h
+++ b/include/system/os-win32.h
@@ -123,7 +123,7 @@ static inline bool is_daemonized(void)
     return false;
 }
 
-static inline int os_mlock(void)
+static inline int os_mlock(bool on_fault G_GNUC_UNUSED)
 {
     return -ENOSYS;
 }
diff --git a/include/system/system.h b/include/system/system.h
index 0cbb43ec30..a7effe7dfd 100644
--- a/include/system/system.h
+++ b/include/system/system.h
@@ -44,10 +44,20 @@ extern int display_opengl;
 extern const char *keyboard_layout;
 extern int old_param;
 extern uint8_t *boot_splash_filedata;
-extern bool enable_mlock;
 extern bool enable_cpu_pm;
 extern QEMUClockType rtc_clock;
 
+typedef enum {
+    MLOCK_OFF = 0,
+    MLOCK_ON,
+    MLOCK_ON_FAULT,
+} MlockState;
+
+bool should_mlock(MlockState);
+bool is_mlock_on_fault(MlockState);
+
+extern MlockState mlock_state;
+
 #define MAX_OPTION_ROMS 16
 typedef struct QEMUOptionRom {
     const char *name;