[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>

1 files changed, 26 insertions, 28 deletions

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