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

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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>
This commit is contained in:
Kohei Tokunaga 2025-04-28 15:39:00 +09:00 • committed by Paolo Bonzini
parent 4cd5a25557
commit 4c7c051719
2 changed files with 11 additions and 0 deletions
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7
include/qemu/cacheflush.h
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@ -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);

4
util/cacheflush.c
View file

@ -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