@samitouri / QOSamiQemu / commits / cf634dfcd8

Allow building qemu tools on 32-bit hosts

Qemu's tools like qemu-img are often needed on 32-bit platforms, although the actual qemu emulators have been discontinued on 32-bit. To allow building the tools on 32-bit this patch implements three small changes: a) The check in meson.build is changed to still error out if the user tries to build qemu-system or qemu-user on a 32-bit platform, but allows building tools (e.g. by "--enable-tools") alone. b) The compile time check in atomic.h now checks against sizeof(uint64_t) so that 32-bit environments can still build successfully, while 128-bit atomic operations are prevented to sneak in. c) Allow linking against libatomic as long as we don't build the qemu-system and qemu-user binaries. Sucessfully tested on the 32-bit big-endian powerpc architecture. Signed-off-by: Helge Deller <deller@gmx.de> Suggested-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Michael Tokarev <mjt@tls.msk.ru> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

Helge Deller committed Apr 5, 2026 at 00:40 UTC cf634dfcd8fc5dded8849d41e2eeaa189b06feb0

2 files changed +15 -7

include/qemu/atomic.h

+3 -3

@@ -58,11 +58,11 @@

59 /*

60 * Sanity check that the size of an atomic operation isn't "overly large".

61 - * Despite the fact that e.g. i686 has 64-bit atomic operations, we do not

61 + * Despite the fact that e.g. x86-64 has 128-bit atomic operations, we do not

62 * want to use them because we ought not need them, and this lets us do a

63 - * bit of sanity checking that other 32-bit hosts might build.

63 + * bit of sanity checking that other 32- and 64-bit hosts might build.

64 */

65 -#define ATOMIC_REG_SIZE sizeof(void *)

65 +#define ATOMIC_REG_SIZE sizeof(uint64_t)

67 /* Weak atomic operations prevent the compiler moving other

68 * loads/stores past the atomic operation load/store. However there is

meson.build

+12 -4

@@ -323,8 +323,8 @@ endif

323 # Compiler flags #

324 ##################

325

326 -if cc.sizeof('void *') < 8

327 - error('QEMU requires a 64-bit CPU host architecture')

326 +if (cc.sizeof('void *') < 8) and (have_system or have_user)

327 + error('QEMU emulator requires a 64-bit CPU host architecture. Only tools may be built for 32-bit.')

328 endif

329

330 foreach lang : all_languages

@@ -423,8 +423,16 @@ endif

423 #

424 # Later checks assume we won't get atomic ops for int128 without

425 # explicitly asking for -latomic, so we must disable GCC's new

426 -# automatic linking with the new -fno-link-libatomic flag

427 -qemu_isa_flags += cc.get_supported_arguments('-fno-link-libatomic')

426 +# automatic linking with the new -fno-link-libatomic flag.

427 +#

428 +# When not building the emulators, but qemu helper tools only

429 +# (e.g. on 32-bit hosts), libatomic is sometimes required and

430 +# thus acceptable.

431 +if (have_system or have_user)

432 + qemu_isa_flags += cc.get_supported_arguments('-fno-link-libatomic')

433 +else

434 + qemu_ldflags += cc.get_supported_link_arguments('-latomic')

435 +endif

436

437 qemu_common_flags = qemu_isa_flags + qemu_common_flags

438