Commit 374aae65 authored by Richard Henderson's avatar Richard Henderson
Browse files

qemu/atomic: Loosen restrictions for 64-bit ILP32 hosts 



We need to coordinate with the TCG_OVERSIZED_GUEST test in cputlb.c,
and allow 64-bit atomics even though sizeof(void *) == 4.

Reviewed-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: default avatarRichard Henderson <rth@twiddle.net>
parent f1079bb8

include/qemu/atomic.h

+26 −8
Original line number Diff line number Diff line
@@ -88,6 +88,24 @@ 
#define smp_read_barrier_depends()   barrier()

#endif



/* 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



/* Weak atomic operations prevent the compiler moving other

 * loads/stores past the atomic operation load/store. However there is
@@ -104,7 +122,7 @@ 


#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);                        \

    })
@@ -112,7 +130,7 @@ 
    __atomic_store_n(ptr, i, __ATOMIC_RELAXED)



#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)
@@ -130,27 +148,27 @@ 


#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;                                             \

    })



#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)



#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;                                               \

    })



#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)
@@ -162,7 +180,7 @@ 
})



#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);                           \

})
@@ -175,7 +193,7 @@ 
})



#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);                             \

})