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authorRichard Henderson <rth@twiddle.net>2017-04-26 10:41:55 -0700
committerRichard Henderson <rth@twiddle.net>2017-06-05 09:25:42 -0700
commit374aae653499f4d405caf32b7fff0c8639113fe4 (patch)
tree5da150e4bd37fb20e9a1965ccdd4cd976eaede16 /include/qemu
parentf1079bb8f9a28495937408acc60a681a7b2536a8 (diff)
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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: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'include/qemu')
-rw-r--r--include/qemu/atomic.h34
1 files 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
+/* 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); \
})