1 files changed, 22 insertions, 5 deletions

diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index cc9b1e182fcf..d69cc6c3f808 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -116,9 +116,26 @@ static inline void spin_time_accum_blocked(u64 start)
 }
 #endif  /* CONFIG_XEN_DEBUG_FS */
 
+/*
+ * Size struct xen_spinlock so it's the same as arch_spinlock_t.
+ */
+#if NR_CPUS < 256
+typedef u8 xen_spinners_t;
+# define inc_spinners(xl) \
+        asm(LOCK_PREFIX " incb %0" : "+m" ((xl)->spinners) : : "memory");
+# define dec_spinners(xl) \
+        asm(LOCK_PREFIX " decb %0" : "+m" ((xl)->spinners) : : "memory");
+#else
+typedef u16 xen_spinners_t;
+# define inc_spinners(xl) \
+        asm(LOCK_PREFIX " incw %0" : "+m" ((xl)->spinners) : : "memory");
+# define dec_spinners(xl) \
+        asm(LOCK_PREFIX " decw %0" : "+m" ((xl)->spinners) : : "memory");
+#endif
+
 struct xen_spinlock {
         unsigned char lock;             /* 0 -> free; 1 -> locked */
-        unsigned short spinners;        /* count of waiting cpus */
+        xen_spinners_t spinners;        /* count of waiting cpus */
 };
 
 static int xen_spin_is_locked(struct arch_spinlock *lock)
@@ -164,8 +181,7 @@ static inline struct xen_spinlock *spinning_lock(struct xen_spinlock *xl)
 
         wmb();                  /* set lock of interest before count */
 
-        asm(LOCK_PREFIX " incw %0"
-            : "+m" (xl->spinners) : : "memory");
+        inc_spinners(xl);
 
         return prev;
 }
@@ -176,8 +192,7 @@ static inline struct xen_spinlock *spinning_lock(struct xen_spinlock *xl)
  */
 static inline void unspinning_lock(struct xen_spinlock *xl, struct xen_spinlock *prev)
 {
-        asm(LOCK_PREFIX " decw %0"
-            : "+m" (xl->spinners) : : "memory");
+        dec_spinners(xl);
         wmb();                  /* decrement count before restoring lock */
         __this_cpu_write(lock_spinners, prev);
 }
@@ -373,6 +388,8 @@ void xen_uninit_lock_cpu(int cpu)
 
 void __init xen_init_spinlocks(void)
 {
+        BUILD_BUG_ON(sizeof(struct xen_spinlock) > sizeof(arch_spinlock_t));
+
         pv_lock_ops.spin_is_locked = xen_spin_is_locked;
         pv_lock_ops.spin_is_contended = xen_spin_is_contended;
         pv_lock_ops.spin_lock = xen_spin_lock;