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X-Received-From: 2607:f8b0:400d:c09::241 Subject: [Qemu-devel] [PATCH v6 03/25] qemu/atomic: Loosen restrictions for 64-bit ILP32 hosts X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: cota@braap.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDKM_2 RSF_0 Z_629925259 SPT_0 We need to coordinate with the TCG_OVERSIZED_GUEST test in cputlb.c, and allow 64-bit atomics even though sizeof(void *) =3D=3D 4. Reviewed-by: Alex Benn=C3=A9e Signed-off-by: Richard Henderson --- include/qemu/atomic.h | 34 ++++++++++++++++++++++++++-------- 1 file changed, 26 insertions(+), 8 deletions(-) diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index 878fa07..e07c797 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -88,6 +88,24 @@ #define smp_read_barrier_depends() barrier() #endif =20 +/* Sanity check that the size of an atomic operation isn't "overly large". + * Despite the fact that e.g. i686 has 64-bit atomic operations, we do not + * want to use them because we ought not need them, and this lets us do a + * bit of sanity checking that other 32-bit hosts might build. + * + * That said, we have a problem on 64-bit ILP32 hosts in that in order to + * sync with TCG_OVERSIZED_GUEST, this must match TCG_TARGET_REG_BITS. + * We'd prefer not want to pull in everything else TCG related, so handle + * those few cases by hand. + * + * Note that x32 is fully detected with __x64_64__ + _ILP32, and that for + * Sparc we always force the use of sparcv9 in configure. + */ +#if defined(__x86_64__) || defined(__sparc__) +# define ATOMIC_REG_SIZE 8 +#else +# define ATOMIC_REG_SIZE sizeof(void *) +#endif =20 /* Weak atomic operations prevent the compiler moving other * loads/stores past the atomic operation load/store. However there is @@ -104,7 +122,7 @@ =20 #define atomic_read(ptr) \ ({ \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ atomic_read__nocheck(ptr); \ }) =20 @@ -112,7 +130,7 @@ __atomic_store_n(ptr, i, __ATOMIC_RELAXED) =20 #define atomic_set(ptr, i) do { \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ atomic_set__nocheck(ptr, i); \ } while(0) =20 @@ -130,27 +148,27 @@ =20 #define atomic_rcu_read(ptr) \ ({ \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ typeof_strip_qual(*ptr) _val; \ atomic_rcu_read__nocheck(ptr, &_val); \ _val; \ }) =20 #define atomic_rcu_set(ptr, i) do { \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ __atomic_store_n(ptr, i, __ATOMIC_RELEASE); \ } while(0) =20 #define atomic_load_acquire(ptr) \ ({ \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ typeof_strip_qual(*ptr) _val; \ __atomic_load(ptr, &_val, __ATOMIC_ACQUIRE); \ _val; \ }) =20 #define atomic_store_release(ptr, i) do { \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ __atomic_store_n(ptr, i, __ATOMIC_RELEASE); \ } while(0) =20 @@ -162,7 +180,7 @@ }) =20 #define atomic_xchg(ptr, i) ({ \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ atomic_xchg__nocheck(ptr, i); \ }) =20 @@ -175,7 +193,7 @@ }) =20 #define atomic_cmpxchg(ptr, old, new) ({ \ - QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ + QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \ atomic_cmpxchg__nocheck(ptr, old, new); \ }) =20 --=20 2.9.3