[Qemu-devel] [PATCH 1/4] memory: add memory_region_flush_rom_device()

[Stefan Hajnoczi <stefanha@redhat.com>]

ROM devices go via MemoryRegionOps->write() callbacks for write
operations and do not dirty/invalidate that memory.  Device emulation
must be able to mark memory ranges that have been modified internally
(e.g. using memory_region_get_ram_ptr()).

Introduce the memory_region_flush_rom_device() API for this purpose.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/exec/memory.h | 18 ++++++++++++++++++
 exec.c                | 12 ++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index cd2f209b64..abe9cc79c0 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1344,6 +1344,24 @@ bool memory_region_snapshot_get_dirty(MemoryRegion *mr,
 void memory_region_reset_dirty(MemoryRegion *mr, hwaddr addr,
                                hwaddr size, unsigned client);
 
+/**
+ * memory_region_flush_rom_device: Mark a range of pages dirty and invalidate
+ *                                 TBs (for self-modifying code).
+ *
+ * The MemoryRegionOps->write() callback of a ROM device must use this function
+ * to mark byte ranges that have been modified internally, such as by directly
+ * accessing the memory returned by memory_region_get_ram_ptr().
+ *
+ * This function marks the range dirty and invalidates TBs so that TCG can
+ * detect self-modifying code.
+ *
+ * @mr: the region being flushed.
+ * @addr: the start, relative to the start of the region, of the range being
+ *        flushed.
+ * @size: the size, in bytes, of the range being flushed.
+ */
+void memory_region_flush_rom_device(MemoryRegion *mr, hwaddr addr, hwaddr size);
+
 /**
  * memory_region_set_readonly: Turn a memory region read-only (or read-write)
  *
diff --git a/exec.c b/exec.c
index 895449f926..105ff21e74 100644
--- a/exec.c
+++ b/exec.c
@@ -3162,6 +3162,18 @@ static void invalidate_and_set_dirty(MemoryRegion *mr, hwaddr addr,
     cpu_physical_memory_set_dirty_range(addr, length, dirty_log_mask);
 }
 
+void memory_region_flush_rom_device(MemoryRegion *mr, hwaddr addr, hwaddr size)
+{
+    /* In principle this function would work on other memory region types too,
+     * but the ROM device use case is the only one where this operation is
+     * necessary.  Other memory regions should use the
+     * address_space_read/write() APIs.
+     */
+    assert(memory_region_is_romd(mr));
+
+    invalidate_and_set_dirty(mr, addr, size);
+}
+
 static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
 {
     unsigned access_size_max = mr->ops->valid.max_access_size;
-- 
2.20.1