[PATCH kvm-unit-test 2/6] Introduce atomic operations

Jason Wang
2010-08-27T05:49:24Z

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
config-x86-common.mak | 1
lib/x86/atomic.c | 38 +++++++++++
lib/x86/atomic.h | 164 +++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 203 insertions(+), 0 deletions(-)
create mode 100644 lib/x86/atomic.c
create mode 100644 lib/x86/atomic.h

diff --git a/config-x86-common.mak b/config-x86-common.mak
index fdb9e3e..b8ca859 100644
--- a/config-x86-common.mak
+++ b/config-x86-common.mak
@@ -10,6 +10,7 @@ cflatobjs += \

cflatobjs += lib/x86/fwcfg.o
cflatobjs += lib/x86/apic.o
+cflatobjs += lib/x86/atomic.o

$(libcflat): LDFLAGS += -nostdlib
$(libcflat): CFLAGS += -ffreestanding -I lib
diff --git a/lib/x86/atomic.c b/lib/x86/atomic.c
new file mode 100644
index 0000000..6697e61
--- /dev/null
+++ b/lib/x86/atomic.c
@@ -0,0 +1,38 @@
+#include <libcflat.h>
+#include "atomic.h"
+
+#ifdef __i386__
+
+u64 atomic64_cmpxchg(atomic64_t *v, u64 old, u64 new)
+{
+ u32 low = new;
+ u32 high = new >> 32;
+
+ asm volatile("lock cmpxchg8b %1\n"
+ : "+A" (old),
+ "+m" (*(volatile long long *)&v->counter)
+ : "b" (low), "c" (high)
+ : "memory"
+ );
+
+ return old;
+}
+
+#else
+
+u64 atomic64_cmpxchg(atomic64_t *v, u64 old, u64 new)
+{
+ u64 ret;
+ u64 _old = old;
+ u64 _new = new;
+
+ asm volatile("lock cmpxchgq %1,%2"
+ : "=a" (ret)
+ : "r" (_new),
+ "m" (*(volatile long *)&v->counter), "0"(_old)
+ : "memory"
+ );
+ return ret;
+}
+
+#endif
diff --git a/lib/x86/atomic.h b/lib/x86/atomic.h
new file mode 100644
index 0000000..de2f033
--- /dev/null
+++ b/lib/x86/atomic.h
@@ -0,0 +1,164 @@
+#ifndef __ATOMIC_H
+#define __ATOMIC_H
+
+typedef struct {
+ volatile int counter;
+} atomic_t;
+
+#ifdef __i386__
+
+/**
+ * atomic_read - read atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically reads the value of @v.
+ */
+static inline int atomic_read(const atomic_t *v)
+{
+ return v->counter;
+}
+
+/**
+ * atomic_set - set atomic variable
+ * @v: pointer of type atomic_t
+ * @i: required value
+ *
+ * Atomically sets the value of @v to @i.
+ */
+static inline void atomic_set(atomic_t *v, int i)
+{
+ v->counter = i;
+}
+
+/**
+ * atomic_inc - increment atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1.
+ */
+static inline void atomic_inc(atomic_t *v)
+{
+ asm volatile("lock incl %0"
+ : "+m" (v->counter));
+}
+
+/**
+ * atomic_dec - decrement atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically decrements @v by 1.
+ */
+static inline void atomic_dec(atomic_t *v)
+{
+ asm volatile("lock decl %0"
+ : "+m" (v->counter));
+}
+
+typedef struct {
+ u64 __attribute__((aligned(8))) counter;
+} atomic64_t;
+
+#define ATOMIC64_INIT(val) { (val) }
+
+/**
+ * atomic64_read - read atomic64 variable
+ * @ptr: pointer to type atomic64_t
+ *
+ * Atomically reads the value of @ptr and returns it.
+ */
+static inline u64 atomic64_read(atomic64_t *ptr)
+{
+ u64 res;
+
+ /*
+ * Note, we inline this atomic64_t primitive because
+ * it only clobbers EAX/EDX and leaves the others
+ * untouched. We also (somewhat subtly) rely on the
+ * fact that cmpxchg8b returns the current 64-bit value
+ * of the memory location we are touching:
+ */
+ asm volatile("mov %%ebx, %%eax\n\t"
+ "mov %%ecx, %%edx\n\t"
+ "lock cmpxchg8b %1\n"
+ : "=&A" (res)
+ : "m" (*ptr)
+ );
+ return res;
+}
+
+u64 atomic64_cmpxchg(atomic64_t *v, u64 old, u64 new);
+
+#elif defined(__x86_64__)
+
+/**
+ * atomic_read - read atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically reads the value of @v.
+ */
+static inline int atomic_read(const atomic_t *v)
+{
+ return v->counter;
+}
+
+/**
+ * atomic_set - set atomic variable
+ * @v: pointer of type atomic_t
+ * @i: required value
+ *
+ * Atomically sets the value of @v to @i.
+ */
+static inline void atomic_set(atomic_t *v, int i)
+{
+ v->counter = i;
+}
+
+/**
+ * atomic_inc - increment atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1.
+ */
+static inline void atomic_inc(atomic_t *v)
+{
+ asm volatile("lock incl %0"
+ : "=m" (v->counter)
+ : "m" (v->counter));
+}
+
+/**
+ * atomic_dec - decrement atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically decrements @v by 1.
+ */
+static inline void atomic_dec(atomic_t *v)
+{
+ asm volatile("lock decl %0"
+ : "=m" (v->counter)
+ : "m" (v->counter));
+}
+
+typedef struct {
+ long long counter;
+} atomic64_t;
+
+#define ATOMIC64_INIT(i) { (i) }
+
+/**
+ * atomic64_read - read atomic64 variable
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically reads the value of @v.
+ * Doesn't imply a read memory barrier.
+ */
+static inline long atomic64_read(const atomic64_t *v)
+{
+ return v->counter;
+}
+
+u64 atomic64_cmpxchg(atomic64_t *v, u64 old, u64 new);
+
+#endif
+
+#endif