[PATCH kvm-unit-tests v2 4/8] Introduce atomic operations

[Jason Wang <jasowang@redhat.com>]

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 config-x86-common.mak |    1 
 lib/x86/atomic.c      |   37 +++++++++++
 lib/x86/atomic.h      |  164 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 202 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..da74ff2
--- /dev/null
+++ b/lib/x86/atomic.c
@@ -0,0 +1,37 @@
+#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 %2,%1"
+                     : "=a" (ret), "+m" (*(volatile long *)&v->counter)
+                     : "r" (_new), "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