[S390] idle time accounting vs. machine checks

A machine check can interrupt the i/o and external interrupt handler
anytime. If the machine check occurs while the interrupt handler is
waking up from idle vtime_start_cpu can get executed a second time
and the int_clock / async_enter_timer values in the lowcore get
clobbered. This can confuse the cpu time accounting.
To fix this problem two changes are needed. First the machine check
handler has to use its own copies of int_clock and async_enter_timer,
named mcck_clock and mcck_enter_timer. Second the nested execution
of vtime_start_cpu has to be prevented. This is done in s390_idle_check
by checking the wait bit in the program status word.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

8 files changed, 123 insertions, 115 deletions

diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 258ba88b7b50..8b1a52a137c5 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -188,15 +188,16 @@ struct s390_idle_data {
 
 DECLARE_PER_CPU(struct s390_idle_data, s390_idle);
 
-void vtime_start_cpu(void);
+void vtime_start_cpu(__u64 int_clock, __u64 enter_timer);
 cputime64_t s390_get_idle_time(int cpu);
 
 #define arch_idle_time(cpu) s390_get_idle_time(cpu)
 
-static inline void s390_idle_check(void)
+static inline void s390_idle_check(struct pt_regs *regs, __u64 int_clock,
+                                   __u64 enter_timer)
 {
-        if ((&__get_cpu_var(s390_idle))->idle_enter != 0ULL)
-                vtime_start_cpu();
+        if (regs->psw.mask & PSW_MASK_WAIT)
+                vtime_start_cpu(int_clock, enter_timer);
 }
 
 static inline int s390_nohz_delay(int cpu)
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index f7e78c79b8b1..2c02d46c3588 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -104,37 +104,39 @@ struct _lowcore {
         /* CPU time accounting values */
         __u64   sync_enter_timer;               /* 0x0250 */
         __u64   async_enter_timer;              /* 0x0258 */
-        __u64   exit_timer;                     /* 0x0260 */
-        __u64   user_timer;                     /* 0x0268 */
-        __u64   system_timer;                   /* 0x0270 */
-        __u64   steal_timer;                    /* 0x0278 */
-        __u64   last_update_timer;              /* 0x0280 */
-        __u64   last_update_clock;              /* 0x0288 */
+        __u64   mcck_enter_timer;               /* 0x0260 */
+        __u64   exit_timer;                     /* 0x0268 */
+        __u64   user_timer;                     /* 0x0270 */
+        __u64   system_timer;                   /* 0x0278 */
+        __u64   steal_timer;                    /* 0x0280 */
+        __u64   last_update_timer;              /* 0x0288 */
+        __u64   last_update_clock;              /* 0x0290 */
 
         /* Current process. */
-        __u32   current_task;                   /* 0x0290 */
-        __u32   thread_info;                    /* 0x0294 */
-        __u32   kernel_stack;                   /* 0x0298 */
+        __u32   current_task;                   /* 0x0298 */
+        __u32   thread_info;                    /* 0x029c */
+        __u32   kernel_stack;                   /* 0x02a0 */
 
         /* Interrupt and panic stack. */
-        __u32   async_stack;                    /* 0x029c */
-        __u32   panic_stack;                    /* 0x02a0 */
+        __u32   async_stack;                    /* 0x02a4 */
+        __u32   panic_stack;                    /* 0x02a8 */
 
         /* Address space pointer. */
-        __u32   kernel_asce;                    /* 0x02a4 */
-        __u32   user_asce;                      /* 0x02a8 */
-        __u32   user_exec_asce;                 /* 0x02ac */
+        __u32   kernel_asce;                    /* 0x02ac */
+        __u32   user_asce;                      /* 0x02b0 */
+        __u32   user_exec_asce;                 /* 0x02b4 */
 
         /* SMP info area */
-        __u32   cpu_nr;                         /* 0x02b0 */
-        __u32   softirq_pending;                /* 0x02b4 */
-        __u32   percpu_offset;                  /* 0x02b8 */
-        __u32   ext_call_fast;                  /* 0x02bc */
-        __u64   int_clock;                      /* 0x02c0 */
-        __u64   clock_comparator;               /* 0x02c8 */
-        __u32   machine_flags;                  /* 0x02d0 */
-        __u32   ftrace_func;                    /* 0x02d4 */
-        __u8    pad_0x02d8[0x0300-0x02d8];      /* 0x02d8 */
+        __u32   cpu_nr;                         /* 0x02b8 */
+        __u32   softirq_pending;                /* 0x02bc */
+        __u32   percpu_offset;                  /* 0x02c0 */
+        __u32   ext_call_fast;                  /* 0x02c4 */
+        __u64   int_clock;                      /* 0x02c8 */
+        __u64   mcck_clock;                     /* 0x02d0 */
+        __u64   clock_comparator;               /* 0x02d8 */
+        __u32   machine_flags;                  /* 0x02e0 */
+        __u32   ftrace_func;                    /* 0x02e4 */
+        __u8    pad_0x02e8[0x0300-0x02e8];      /* 0x02e8 */
 
         /* Interrupt response block */
         __u8    irb[64];                        /* 0x0300 */
@@ -232,38 +234,40 @@ struct _lowcore {
         /* CPU accounting and timing values. */
         __u64   sync_enter_timer;               /* 0x02a0 */
         __u64   async_enter_timer;              /* 0x02a8 */
-        __u64   exit_timer;                     /* 0x02b0 */
-        __u64   user_timer;                     /* 0x02b8 */
-        __u64   system_timer;                   /* 0x02c0 */
-        __u64   steal_timer;                    /* 0x02c8 */
-        __u64   last_update_timer;              /* 0x02d0 */
-        __u64   last_update_clock;              /* 0x02d8 */
+        __u64   mcck_enter_timer;               /* 0x02b0 */
+        __u64   exit_timer;                     /* 0x02b8 */
+        __u64   user_timer;                     /* 0x02c0 */
+        __u64   system_timer;                   /* 0x02c8 */
+        __u64   steal_timer;                    /* 0x02d0 */
+        __u64   last_update_timer;              /* 0x02d8 */
+        __u64   last_update_clock;              /* 0x02e0 */
 
         /* Current process. */
-        __u64   current_task;                   /* 0x02e0 */
-        __u64   thread_info;                    /* 0x02e8 */
-        __u64   kernel_stack;                   /* 0x02f0 */
+        __u64   current_task;                   /* 0x02e8 */
+        __u64   thread_info;                    /* 0x02f0 */
+        __u64   kernel_stack;                   /* 0x02f8 */
 
         /* Interrupt and panic stack. */
-        __u64   async_stack;                    /* 0x02f8 */
-        __u64   panic_stack;                    /* 0x0300 */
+        __u64   async_stack;                    /* 0x0300 */
+        __u64   panic_stack;                    /* 0x0308 */
 
         /* Address space pointer. */
-        __u64   kernel_asce;                    /* 0x0308 */
-        __u64   user_asce;                      /* 0x0310 */
-        __u64   user_exec_asce;                 /* 0x0318 */
+        __u64   kernel_asce;                    /* 0x0310 */
+        __u64   user_asce;                      /* 0x0318 */
+        __u64   user_exec_asce;                 /* 0x0320 */
 
         /* SMP info area */
-        __u32   cpu_nr;                         /* 0x0320 */
-        __u32   softirq_pending;                /* 0x0324 */
-        __u64   percpu_offset;                  /* 0x0328 */
-        __u64   ext_call_fast;                  /* 0x0330 */
-        __u64   int_clock;                      /* 0x0338 */
-        __u64   clock_comparator;               /* 0x0340 */
-        __u64   vdso_per_cpu_data;              /* 0x0348 */
-        __u64   machine_flags;                  /* 0x0350 */
-        __u64   ftrace_func;                    /* 0x0358 */
-        __u8    pad_0x0368[0x0380-0x0360];      /* 0x0360 */
+        __u32   cpu_nr;                         /* 0x0328 */
+        __u32   softirq_pending;                /* 0x032c */
+        __u64   percpu_offset;                  /* 0x0330 */
+        __u64   ext_call_fast;                  /* 0x0338 */
+        __u64   int_clock;                      /* 0x0340 */
+        __u64   mcck_clock;                     /* 0x0348 */
+        __u64   clock_comparator;               /* 0x0350 */
+        __u64   vdso_per_cpu_data;              /* 0x0358 */
+        __u64   machine_flags;                  /* 0x0360 */
+        __u64   ftrace_func;                    /* 0x0368 */
+        __u8    pad_0x0370[0x0380-0x0370];      /* 0x0370 */
 
         /* Interrupt response block. */
         __u8    irb[64];                        /* 0x0380 */
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index 32b1ede69858..816d81f479c0 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -112,6 +112,7 @@ int main(void)
         DEFINE(__LC_RETURN_MCCK_PSW, offsetof(struct _lowcore, return_mcck_psw));
         DEFINE(__LC_SYNC_ENTER_TIMER, offsetof(struct _lowcore, sync_enter_timer));
         DEFINE(__LC_ASYNC_ENTER_TIMER, offsetof(struct _lowcore, async_enter_timer));
+        DEFINE(__LC_MCCK_ENTER_TIMER, offsetof(struct _lowcore, mcck_enter_timer));
         DEFINE(__LC_EXIT_TIMER, offsetof(struct _lowcore, exit_timer));
         DEFINE(__LC_USER_TIMER, offsetof(struct _lowcore, user_timer));
         DEFINE(__LC_SYSTEM_TIMER, offsetof(struct _lowcore, system_timer));
@@ -127,6 +128,7 @@ int main(void)
         DEFINE(__LC_USER_ASCE, offsetof(struct _lowcore, user_asce));
         DEFINE(__LC_USER_EXEC_ASCE, offsetof(struct _lowcore, user_exec_asce));
         DEFINE(__LC_INT_CLOCK, offsetof(struct _lowcore, int_clock));
+        DEFINE(__LC_MCCK_CLOCK, offsetof(struct _lowcore, mcck_clock));
         DEFINE(__LC_MACHINE_FLAGS, offsetof(struct _lowcore, machine_flags));
         DEFINE(__LC_FTRACE_FUNC, offsetof(struct _lowcore, ftrace_func));
         DEFINE(__LC_IRB, offsetof(struct _lowcore, irb));
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 07d849995dac..0e2b16241dfa 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -742,15 +742,14 @@ __critical_end:
 
         .globl mcck_int_handler
 mcck_int_handler:
-        stck    __LC_INT_CLOCK
+        stck    __LC_MCCK_CLOCK
         spt     __LC_CPU_TIMER_SAVE_AREA        # revalidate cpu timer
         lm      %r0,%r15,__LC_GPREGS_SAVE_AREA  # revalidate gprs
         SAVE_ALL_BASE __LC_SAVE_AREA+32
         la      %r12,__LC_MCK_OLD_PSW
         tm      __LC_MCCK_CODE,0x80     # system damage?
         bo      BASED(mcck_int_main)    # yes -> rest of mcck code invalid
-        mvc     __LC_SAVE_AREA+52(8),__LC_ASYNC_ENTER_TIMER
-        mvc     __LC_ASYNC_ENTER_TIMER(8),__LC_CPU_TIMER_SAVE_AREA
+        mvc     __LC_MCCK_ENTER_TIMER(8),__LC_CPU_TIMER_SAVE_AREA
         tm      __LC_MCCK_CODE+5,0x02   # stored cpu timer value valid?
         bo      BASED(1f)
         la      %r14,__LC_SYNC_ENTER_TIMER
@@ -764,7 +763,7 @@ mcck_int_handler:
         bl      BASED(0f)
         la      %r14,__LC_LAST_UPDATE_TIMER
 0:      spt     0(%r14)
-        mvc     __LC_ASYNC_ENTER_TIMER(8),0(%r14)
+        mvc     __LC_MCCK_ENTER_TIMER(8),0(%r14)
 1:      tm      __LC_MCCK_CODE+2,0x09   # mwp + ia of old psw valid?
         bno     BASED(mcck_int_main)    # no -> skip cleanup critical
         tm      __LC_MCK_OLD_PSW+1,0x01 # test problem state bit
@@ -786,9 +785,9 @@ mcck_int_main:
         bno     BASED(mcck_no_vtime)    # no -> skip cleanup critical
         tm      SP_PSW+1(%r15),0x01     # interrupting from user ?
         bz      BASED(mcck_no_vtime)
-        UPDATE_VTIME __LC_EXIT_TIMER,__LC_ASYNC_ENTER_TIMER,__LC_USER_TIMER
+        UPDATE_VTIME __LC_EXIT_TIMER,__LC_MCCK_ENTER_TIMER,__LC_USER_TIMER
         UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
-        mvc     __LC_LAST_UPDATE_TIMER(8),__LC_ASYNC_ENTER_TIMER
+        mvc     __LC_LAST_UPDATE_TIMER(8),__LC_MCCK_ENTER_TIMER
 mcck_no_vtime:
         l       %r9,__LC_THREAD_INFO    # load pointer to thread_info struct
         la      %r2,SP_PTREGS(%r15)     # load pt_regs
@@ -811,7 +810,6 @@ mcck_no_vtime:
 mcck_return:
         mvc     __LC_RETURN_MCCK_PSW(8),SP_PSW(%r15) # move return PSW
         ni      __LC_RETURN_MCCK_PSW+1,0xfd # clear wait state bit
-        mvc     __LC_ASYNC_ENTER_TIMER(8),__LC_SAVE_AREA+52
         tm      __LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?
         bno     BASED(0f)
         lm      %r0,%r15,SP_R0(%r15)    # load gprs 0-15
@@ -934,15 +932,16 @@ cleanup_critical:
 
 cleanup_system_call:
         mvc     __LC_RETURN_PSW(8),0(%r12)
-        c       %r12,BASED(.Lmck_old_psw)
-        be      BASED(0f)
-        la      %r12,__LC_SAVE_AREA+16
-        b       BASED(1f)
-0:      la      %r12,__LC_SAVE_AREA+32
-1:
         clc     __LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn+4)
         bh      BASED(0f)
+        mvc     __LC_SYNC_ENTER_TIMER(8),__LC_MCCK_ENTER_TIMER
+        c       %r12,BASED(.Lmck_old_psw)
+        be      BASED(0f)
         mvc     __LC_SYNC_ENTER_TIMER(8),__LC_ASYNC_ENTER_TIMER
+0:      c       %r12,BASED(.Lmck_old_psw)
+        la      %r12,__LC_SAVE_AREA+32
+        be      BASED(0f)
+        la      %r12,__LC_SAVE_AREA+16
 0:      clc     __LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn+8)
         bhe     BASED(cleanup_vtime)
         clc     __LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn)
@@ -984,16 +983,19 @@ cleanup_sysc_tif:
 cleanup_sysc_restore:
         clc     4(4,%r12),BASED(cleanup_sysc_restore_insn)
         be      BASED(2f)
+        mvc     __LC_EXIT_TIMER(8),__LC_MCCK_ENTER_TIMER
+        c       %r12,BASED(.Lmck_old_psw)
+        be      BASED(0f)
         mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
-        clc     4(4,%r12),BASED(cleanup_sysc_restore_insn+4)
+0:      clc     4(4,%r12),BASED(cleanup_sysc_restore_insn+4)
         be      BASED(2f)
         mvc     __LC_RETURN_PSW(8),SP_PSW(%r15)
         c       %r12,BASED(.Lmck_old_psw)
-        bne     BASED(0f)
-        mvc     __LC_SAVE_AREA+32(16),SP_R12(%r15)
-        b       BASED(1f)
-0:      mvc     __LC_SAVE_AREA+16(16),SP_R12(%r15)
-1:      lm      %r0,%r11,SP_R0(%r15)
+        la      %r12,__LC_SAVE_AREA+32
+        be      BASED(1f)
+        la      %r12,__LC_SAVE_AREA+16
+1:      mvc     0(16,%r12),SP_R12(%r15)
+        lm      %r0,%r11,SP_R0(%r15)
         l       %r15,SP_R15(%r15)
 2:      la      %r12,__LC_RETURN_PSW
         br      %r14
@@ -1009,19 +1011,15 @@ cleanup_io_tif:
 
 cleanup_io_restore:
         clc     4(4,%r12),BASED(cleanup_io_restore_insn)
-        be      BASED(2f)
-        mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
+        be      BASED(1f)
+        mvc     __LC_EXIT_TIMER(8),__LC_MCCK_ENTER_TIMER
         clc     4(4,%r12),BASED(cleanup_io_restore_insn+4)
-        be      BASED(2f)
+        be      BASED(1f)
         mvc     __LC_RETURN_PSW(8),SP_PSW(%r15)
-        c       %r12,BASED(.Lmck_old_psw)
-        bne     BASED(0f)
         mvc     __LC_SAVE_AREA+32(16),SP_R12(%r15)
-        b       BASED(1f)
-0:      mvc     __LC_SAVE_AREA+16(16),SP_R12(%r15)
-1:      lm      %r0,%r11,SP_R0(%r15)
+        lm      %r0,%r11,SP_R0(%r15)
         l       %r15,SP_R15(%r15)
-2:      la      %r12,__LC_RETURN_PSW
+1:      la      %r12,__LC_RETURN_PSW
         br      %r14
 cleanup_io_restore_insn:
         .long   io_done - 4 + 0x80000000
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 860cea1d1c8a..6536f5ca46f5 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -725,7 +725,7 @@ __critical_end:
  */
         .globl mcck_int_handler
 mcck_int_handler:
-        stck    __LC_INT_CLOCK
+        stck    __LC_MCCK_CLOCK
         la      %r1,4095                # revalidate r1
         spt     __LC_CPU_TIMER_SAVE_AREA-4095(%r1)      # revalidate cpu timer
         lmg     %r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1)# revalidate gprs
@@ -734,8 +734,7 @@ mcck_int_handler:
         tm      __LC_MCCK_CODE,0x80     # system damage?
         jo      mcck_int_main           # yes -> rest of mcck code invalid
         la      %r14,4095
-        mvc     __LC_SAVE_AREA+104(8),__LC_ASYNC_ENTER_TIMER
-        mvc     __LC_ASYNC_ENTER_TIMER(8),__LC_CPU_TIMER_SAVE_AREA-4095(%r14)
+        mvc     __LC_MCCK_ENTER_TIMER(8),__LC_CPU_TIMER_SAVE_AREA-4095(%r14)
         tm      __LC_MCCK_CODE+5,0x02   # stored cpu timer value valid?
         jo      1f
         la      %r14,__LC_SYNC_ENTER_TIMER
@@ -749,7 +748,7 @@ mcck_int_handler:
         jl      0f
         la      %r14,__LC_LAST_UPDATE_TIMER
 0:      spt     0(%r14)
-        mvc     __LC_ASYNC_ENTER_TIMER(8),0(%r14)
+        mvc     __LC_MCCK_ENTER_TIMER(8),0(%r14)
 1:      tm      __LC_MCCK_CODE+2,0x09   # mwp + ia of old psw valid?
         jno     mcck_int_main           # no -> skip cleanup critical
         tm      __LC_MCK_OLD_PSW+1,0x01 # test problem state bit
@@ -770,9 +769,9 @@ mcck_int_main:
         jno     mcck_no_vtime           # no -> no timer update
         tm      SP_PSW+1(%r15),0x01     # interrupting from user ?
         jz      mcck_no_vtime
-        UPDATE_VTIME __LC_EXIT_TIMER,__LC_ASYNC_ENTER_TIMER,__LC_USER_TIMER
+        UPDATE_VTIME __LC_EXIT_TIMER,__LC_MCCK_ENTER_TIMER,__LC_USER_TIMER
         UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
-        mvc     __LC_LAST_UPDATE_TIMER(8),__LC_ASYNC_ENTER_TIMER
+        mvc     __LC_LAST_UPDATE_TIMER(8),__LC_MCCK_ENTER_TIMER
 mcck_no_vtime:
         lg      %r9,__LC_THREAD_INFO    # load pointer to thread_info struct
         la      %r2,SP_PTREGS(%r15)     # load pt_regs
@@ -794,7 +793,6 @@ mcck_return:
         mvc     __LC_RETURN_MCCK_PSW(16),SP_PSW(%r15) # move return PSW
         ni      __LC_RETURN_MCCK_PSW+1,0xfd # clear wait state bit
         lmg     %r0,%r15,SP_R0(%r15)    # load gprs 0-15
-        mvc     __LC_ASYNC_ENTER_TIMER(8),__LC_SAVE_AREA+104
         tm      __LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?
         jno     0f
         stpt    __LC_EXIT_TIMER
@@ -909,15 +907,16 @@ cleanup_critical:
 
 cleanup_system_call:
         mvc     __LC_RETURN_PSW(16),0(%r12)
-        cghi    %r12,__LC_MCK_OLD_PSW
-        je      0f
-        la      %r12,__LC_SAVE_AREA+32
-        j       1f
-0:      la      %r12,__LC_SAVE_AREA+64
-1:
         clc     __LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn+8)
         jh      0f
+        mvc     __LC_SYNC_ENTER_TIMER(8),__LC_MCCK_ENTER_TIMER
+        cghi    %r12,__LC_MCK_OLD_PSW
+        je      0f
         mvc     __LC_SYNC_ENTER_TIMER(8),__LC_ASYNC_ENTER_TIMER
+0:      cghi    %r12,__LC_MCK_OLD_PSW
+        la      %r12,__LC_SAVE_AREA+64
+        je      0f
+        la      %r12,__LC_SAVE_AREA+32
 0:      clc     __LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn+16)
         jhe     cleanup_vtime
         clc     __LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn)
@@ -958,19 +957,22 @@ cleanup_sysc_tif:
 
 cleanup_sysc_restore:
         clc     8(8,%r12),BASED(cleanup_sysc_restore_insn)
-        je      3f
+        je      2f
         clc     8(8,%r12),BASED(cleanup_sysc_restore_insn+8)
         jhe     0f
+        mvc     __LC_EXIT_TIMER(8),__LC_MCCK_ENTER_TIMER
+        cghi    %r12,__LC_MCK_OLD_PSW
+        je      0f
         mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
 0:      mvc     __LC_RETURN_PSW(16),SP_PSW(%r15)
         cghi    %r12,__LC_MCK_OLD_PSW
-        jne     1f
-        mvc     __LC_SAVE_AREA+64(32),SP_R12(%r15)
-        j       2f
-1:      mvc     __LC_SAVE_AREA+32(32),SP_R12(%r15)
-2:      lmg     %r0,%r11,SP_R0(%r15)
+        la      %r12,__LC_SAVE_AREA+64
+        je      1f
+        la      %r12,__LC_SAVE_AREA+32
+1:      mvc     0(32,%r12),SP_R12(%r15)
+        lmg     %r0,%r11,SP_R0(%r15)
         lg      %r15,SP_R15(%r15)
-3:      la      %r12,__LC_RETURN_PSW
+2:      la      %r12,__LC_RETURN_PSW
         br      %r14
 cleanup_sysc_restore_insn:
         .quad   sysc_done - 4
@@ -984,19 +986,15 @@ cleanup_io_tif:
 
 cleanup_io_restore:
         clc     8(8,%r12),BASED(cleanup_io_restore_insn)
-        je      3f
+        je      1f
         clc     8(8,%r12),BASED(cleanup_io_restore_insn+8)
         jhe     0f
-        mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
+        mvc     __LC_EXIT_TIMER(8),__LC_MCCK_ENTER_TIMER
 0:      mvc     __LC_RETURN_PSW(16),SP_PSW(%r15)
-        cghi    %r12,__LC_MCK_OLD_PSW
-        jne     1f
         mvc     __LC_SAVE_AREA+64(32),SP_R12(%r15)
-        j       2f
-1:      mvc     __LC_SAVE_AREA+32(32),SP_R12(%r15)
-2:      lmg     %r0,%r11,SP_R0(%r15)
+        lmg     %r0,%r11,SP_R0(%r15)
         lg      %r15,SP_R15(%r15)
-3:      la      %r12,__LC_RETURN_PSW
+1:      la      %r12,__LC_RETURN_PSW
         br      %r14
 cleanup_io_restore_insn:
         .quad   io_done - 4
diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 015e27da40eb..ac151399ef34 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -255,7 +255,8 @@ void notrace s390_do_machine_check(struct pt_regs *regs)
         int umode;
 
         nmi_enter();
-        s390_idle_check();
+        s390_idle_check(regs, S390_lowcore.mcck_clock,
+                        S390_lowcore.mcck_enter_timer);
 
         mci = (struct mci *) &S390_lowcore.mcck_interruption_code;
         mcck = &__get_cpu_var(cpu_mcck);
diff --git a/arch/s390/kernel/s390_ext.c b/arch/s390/kernel/s390_ext.c
index 59618bcd99b7..9ce641b5291f 100644
--- a/arch/s390/kernel/s390_ext.c
+++ b/arch/s390/kernel/s390_ext.c
@@ -120,7 +120,8 @@ void __irq_entry do_extint(struct pt_regs *regs, unsigned short code)
         struct pt_regs *old_regs;
 
         old_regs = set_irq_regs(regs);
-        s390_idle_check();
+        s390_idle_check(regs, S390_lowcore.int_clock,
+                        S390_lowcore.async_enter_timer);
         irq_enter();
         if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
                 /* Serve timer interrupts first. */
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index b59a812a010e..3479f1b0d4e0 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -121,32 +121,35 @@ void account_system_vtime(struct task_struct *tsk)
 }
 EXPORT_SYMBOL_GPL(account_system_vtime);
 
-void vtime_start_cpu(void)
+void vtime_start_cpu(__u64 int_clock, __u64 enter_timer)
 {
         struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
         struct vtimer_queue *vq = &__get_cpu_var(virt_cpu_timer);
         __u64 idle_time, expires;
 
+        if (idle->idle_enter == 0ULL)
+                return;
+
         /* Account time spent with enabled wait psw loaded as idle time. */
-        idle_time = S390_lowcore.int_clock - idle->idle_enter;
+        idle_time = int_clock - idle->idle_enter;
         account_idle_time(idle_time);
         S390_lowcore.steal_timer +=
                 idle->idle_enter - S390_lowcore.last_update_clock;
-        S390_lowcore.last_update_clock = S390_lowcore.int_clock;
+        S390_lowcore.last_update_clock = int_clock;
 
         /* Account system time spent going idle. */
         S390_lowcore.system_timer += S390_lowcore.last_update_timer - vq->idle;
-        S390_lowcore.last_update_timer = S390_lowcore.async_enter_timer;
+        S390_lowcore.last_update_timer = enter_timer;
 
         /* Restart vtime CPU timer */
         if (vq->do_spt) {
                 /* Program old expire value but first save progress. */
-                expires = vq->idle - S390_lowcore.async_enter_timer;
+                expires = vq->idle - enter_timer;
                 expires += get_vtimer();
                 set_vtimer(expires);
         } else {
                 /* Don't account the CPU timer delta while the cpu was idle. */
-                vq->elapsed -= vq->idle - S390_lowcore.async_enter_timer;
+                vq->elapsed -= vq->idle - enter_timer;
         }
 
         idle->sequence++;