physmem: factor out RAM/ROMD check in memory_access_is_direct()

Let's factor more of the generic "is this directly accessible" check,
independent of the "write" condition out.

Note that the "!mr->rom_device" check in the write case essentially
disallows the memory_region_is_romd() condition again. Further note that
RAM DEVICE regions are also RAM regions, so we can check for RAM+ROMD
first.

This is a preparation for further changes.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20250210084648.33798-3-david@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 5cd7574..cb35c38 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2997,6 +2997,10 @@ bool prepare_mmio_access(MemoryRegion *mr);
 
 static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write)
 {
+    /* ROM DEVICE regions only allow direct access if in ROMD mode. */
+    if (!memory_region_is_ram(mr) && !memory_region_is_romd(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
@@ -3006,11 +3010,9 @@ static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write)
         return false;
     }
     if (is_write) {
-        return memory_region_is_ram(mr) && !mr->readonly &&
-               !mr->rom_device;
-    } else {
-        return memory_region_is_ram(mr) || memory_region_is_romd(mr);
+        return !mr->readonly && !mr->rom_device;
     }
+    return true;
 }
 
 /**