include/host: Split out atomic128-ldst.h

Separates the aarch64-specific portion into its own file.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 106 insertions, 0 deletions

diff --git a/host/include/aarch64/host/atomic128-ldst.h b/host/include/aarch64/host/atomic128-ldst.h
new file mode 100644
index 0000000..bd61fce
--- /dev/null
+++ b/host/include/aarch64/host/atomic128-ldst.h
@@ -0,0 +1,49 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Load/store for 128-bit atomic operations, AArch64 version.
+ *
+ * Copyright (C) 2018, 2023 Linaro, Ltd.
+ *
+ * See docs/devel/atomics.rst for discussion about the guarantees each
+ * atomic primitive is meant to provide.
+ */
+
+#ifndef AARCH64_ATOMIC128_LDST_H
+#define AARCH64_ATOMIC128_LDST_H
+
+/* Through gcc 10, aarch64 has no support for 128-bit atomics.  */
+#if !defined(CONFIG_ATOMIC128) && !defined(CONFIG_USER_ONLY)
+/* We can do better than cmpxchg for AArch64.  */
+static inline Int128 atomic16_read(Int128 *ptr)
+{
+    uint64_t l, h;
+    uint32_t tmp;
+
+    /* The load must be paired with the store to guarantee not tearing.  */
+    asm("0: ldxp %[l], %[h], %[mem]\n\t"
+        "stxp %w[tmp], %[l], %[h], %[mem]\n\t"
+        "cbnz %w[tmp], 0b"
+        : [mem] "+m"(*ptr), [tmp] "=r"(tmp), [l] "=r"(l), [h] "=r"(h));
+
+    return int128_make128(l, h);
+}
+
+static inline void atomic16_set(Int128 *ptr, Int128 val)
+{
+    uint64_t l = int128_getlo(val), h = int128_gethi(val);
+    uint64_t t1, t2;
+
+    /* Load into temporaries to acquire the exclusive access lock.  */
+    asm("0: ldxp %[t1], %[t2], %[mem]\n\t"
+        "stxp %w[t1], %[l], %[h], %[mem]\n\t"
+        "cbnz %w[t1], 0b"
+        : [mem] "+m"(*ptr), [t1] "=&r"(t1), [t2] "=&r"(t2)
+        : [l] "r"(l), [h] "r"(h));
+}
+
+# define HAVE_ATOMIC128 1
+#else
+#include "host/include/generic/host/atomic128-ldst.h"
+#endif
+
+#endif /* AARCH64_ATOMIC128_LDST_H */
diff --git a/host/include/generic/host/atomic128-ldst.h b/host/include/generic/host/atomic128-ldst.h
new file mode 100644
index 0000000..e7354a9
--- /dev/null
+++ b/host/include/generic/host/atomic128-ldst.h
@@ -0,0 +1,57 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Load/store for 128-bit atomic operations, generic version.
+ *
+ * Copyright (C) 2018, 2023 Linaro, Ltd.
+ *
+ * See docs/devel/atomics.rst for discussion about the guarantees each
+ * atomic primitive is meant to provide.
+ */
+
+#ifndef HOST_ATOMIC128_LDST_H
+#define HOST_ATOMIC128_LDST_H
+
+#if defined(CONFIG_ATOMIC128)
+static inline Int128 atomic16_read(Int128 *ptr)
+{
+    Int128Alias r;
+
+    r.i = qatomic_read__nocheck((__int128_t *)ptr);
+    return r.s;
+}
+
+static inline void atomic16_set(Int128 *ptr, Int128 val)
+{
+    Int128Alias v;
+
+    v.s = val;
+    qatomic_set__nocheck((__int128_t *)ptr, v.i);
+}
+
+# define HAVE_ATOMIC128 1
+#elif !defined(CONFIG_USER_ONLY) && HAVE_CMPXCHG128
+static inline Int128 atomic16_read(Int128 *ptr)
+{
+    /* Maybe replace 0 with 0, returning the old value.  */
+    Int128 z = int128_make64(0);
+    return atomic16_cmpxchg(ptr, z, z);
+}
+
+static inline void atomic16_set(Int128 *ptr, Int128 val)
+{
+    Int128 old = *ptr, cmp;
+    do {
+        cmp = old;
+        old = atomic16_cmpxchg(ptr, cmp, val);
+    } while (int128_ne(old, cmp));
+}
+
+# define HAVE_ATOMIC128 1
+#else
+/* Fallback definitions that must be optimized away, or error.  */
+Int128 QEMU_ERROR("unsupported atomic") atomic16_read(Int128 *ptr);
+void QEMU_ERROR("unsupported atomic") atomic16_set(Int128 *ptr, Int128 val);
+# define HAVE_ATOMIC128 0
+#endif
+
+#endif /* HOST_ATOMIC128_LDST_H */