util/cacheflush.c: Update cache flushing mechanism for Emscripten

Although __builtin___clear_cache is used to flush the instruction cache for
a specified memory region, this operation doesn't apply to wasm, as its
memory isn't executable. Moreover, Emscripten does not support this builtin
and fails to compile it with the following error.

> fatal error: error in backend: llvm.clear_cache is not supported on wasm

To resolve this, this commit removes the call to __builtin___clear_cache for
Emscripten build.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/r/2926a798fa52a3a5b11c3df4edd1643d2b7cdcb9.1745820062.git.ktokunaga.mail@gmail.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/include/qemu/cacheflush.h b/include/qemu/cacheflush.h
index ae20bcda733de7004be685cb3a78cce393672375..76eb55d818db908a4fa267c5e09c54937f449552 100644 (file)
--- a/include/qemu/cacheflush.h
+++ b/include/qemu/cacheflush.h
@@ -26,6 +26,13 @@ static inline void flush_idcache_range(uintptr_t rx, uintptr_t rw, size_t len)
     /* icache is coherent and does not require flushing. */
 }
 
+#elif defined(EMSCRIPTEN)
+
+static inline void flush_idcache_range(uintptr_t rx, uintptr_t rw, size_t len)
+{
+    /* Wasm doesn't have executable region of memory. */
+}
+
 #else
 
 void flush_idcache_range(uintptr_t rx, uintptr_t rw, size_t len);

diff --git a/util/cacheflush.c b/util/cacheflush.c
index 1d12899a392235ffd73c476310aaf60c740b089f..17c58918de60dd576ad7ef6066d9a954991b7f42 100644 (file)
--- a/util/cacheflush.c
+++ b/util/cacheflush.c
@@ -229,6 +229,10 @@ static void __attribute__((constructor)) init_cache_info(void)
 
 /* Caches are coherent and do not require flushing; symbol inline. */
 
+#elif defined(EMSCRIPTEN)
+
+/* Wasm doesn't have executable region of memory. */
+
 #elif defined(__aarch64__) && !defined(CONFIG_WIN32)
 /*
  * For Windows, we use generic implementation of flush_idcache_range, that