1 files changed, 22 insertions, 29 deletions

diff --git a/arch/s390/include/asm/system.h b/arch/s390/include/asm/system.h
index 1f2ebc4afd82..3ad16dbf622e 100644
--- a/arch/s390/include/asm/system.h
+++ b/arch/s390/include/asm/system.h
@@ -85,14 +85,16 @@ static inline void restore_access_regs(unsigned int *acrs)
         asm volatile("lam 0,15,%0" : : "Q" (*acrs));
 }
 
-#define switch_to(prev,next,last) do {                                       \
-        if (prev == next)                                                    \
-                break;                                                       \
-        save_fp_regs(&prev->thread.fp_regs);                                 \
-        restore_fp_regs(&next->thread.fp_regs);                              \
-        save_access_regs(&prev->thread.acrs[0]);                             \
-        restore_access_regs(&next->thread.acrs[0]);                          \
-        prev = __switch_to(prev,next);                                       \
+#define switch_to(prev,next,last) do {                                  \
+        if (prev->mm) {                                                 \
+                save_fp_regs(&prev->thread.fp_regs);                    \
+                save_access_regs(&prev->thread.acrs[0]);                \
+        }                                                               \
+        if (next->mm) {                                                 \
+                restore_fp_regs(&next->thread.fp_regs);                 \
+                restore_access_regs(&next->thread.acrs[0]);             \
+        }                                                               \
+        prev = __switch_to(prev,next);                                  \
 } while (0)
 
 extern void account_vtime(struct task_struct *, struct task_struct *);
@@ -418,30 +420,21 @@ extern void smp_ctl_clear_bit(int cr, int bit);
 
 #endif /* CONFIG_SMP */
 
-static inline unsigned int stfl(void)
-{
-        asm volatile(
-                "       .insn   s,0xb2b10000,0(0)\n" /* stfl */
-                "0:\n"
-                EX_TABLE(0b,0b));
-        return S390_lowcore.stfl_fac_list;
-}
+#define MAX_FACILITY_BIT (256*8)        /* stfle_fac_list has 256 bytes */
 
-static inline int __stfle(unsigned long long *list, int doublewords)
+/*
+ * The test_facility function uses the bit odering where the MSB is bit 0.
+ * That makes it easier to query facility bits with the bit number as
+ * documented in the Principles of Operation.
+ */
+static inline int test_facility(unsigned long nr)
 {
-        typedef struct { unsigned long long _[doublewords]; } addrtype;
-        register unsigned long __nr asm("0") = doublewords - 1;
-
-        asm volatile(".insn s,0xb2b00000,%0" /* stfle */
-                     : "=m" (*(addrtype *) list), "+d" (__nr) : : "cc");
-        return __nr + 1;
-}
+        unsigned char *ptr;
 
-static inline int stfle(unsigned long long *list, int doublewords)
-{
-        if (!(stfl() & (1UL << 24)))
-                return -EOPNOTSUPP;
-        return __stfle(list, doublewords);
+        if (nr >= MAX_FACILITY_BIT)
+                return 0;
+        ptr = (unsigned char *) &S390_lowcore.stfle_fac_list + (nr >> 3);
+        return (*ptr & (0x80 >> (nr & 7))) != 0;
 }
 
 static inline unsigned short stap(void)