s390/nmi: use the normal asynchronous stack for machine checks

If a machine checks is received while the CPU is in the kernel, only
the s390_do_machine_check function will be called. The call to
s390_handle_mcck is postponed until the CPU returns to user space.
Because of this it is safe to use the asynchronous stack for machine
checks even if the CPU is already handling an interrupt.

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

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index a721c39d014d0729163083145235b98db09e996d..21c1219122afe865d2564dd7bf293c857b2220ee 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -83,7 +83,7 @@ _PIF_WORK     = (_PIF_PER_TRAP)
 #endif
        .endm
 
-       .macro  SWITCH_ASYNC savearea,stack,shift,timer
+       .macro  SWITCH_ASYNC savearea,timer
        tmhh    %r8,0x0001              # interrupting from user ?
        jnz     1f
        lgr     %r14,%r9
@@ -94,16 +94,16 @@ _PIF_WORK   = (_PIF_PER_TRAP)
        brasl   %r14,cleanup_critical
        tmhh    %r8,0x0001              # retest problem state after cleanup
        jnz     1f
-0:     lg      %r14,\stack             # are we already on the target stack?
+0:     lg      %r14,__LC_ASYNC_STACK   # are we already on the async stack?
        slgr    %r14,%r15
-       srag    %r14,%r14,\shift
+       srag    %r14,%r14,STACK_SHIFT
        jnz     2f
-       CHECK_STACK 1<<\shift,\savearea
+       CHECK_STACK 1<<STACK_SHIFT,\savearea
        aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
        j       3f
 1:     LAST_BREAK %r14
        UPDATE_VTIME %r14,%r15,\timer
-2:     lg      %r15,\stack             # load target stack
+2:     lg      %r15,__LC_ASYNC_STACK   # load async stack
 3:     la      %r11,STACK_FRAME_OVERHEAD(%r15)
        .endm
 
@@ -539,8 +539,7 @@ ENTRY(io_int_handler)
        lg      %r12,__LC_THREAD_INFO
        larl    %r13,cleanup_critical
        lmg     %r8,%r9,__LC_IO_OLD_PSW
-       SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_STACK,STACK_SHIFT,\
-                    __LC_ASYNC_ENTER_TIMER
+       SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_ENTER_TIMER
        stmg    %r0,%r7,__PT_R0(%r11)
        mvc     __PT_R8(64,%r11),__LC_SAVE_AREA_ASYNC
        stmg    %r8,%r9,__PT_PSW(%r11)
@@ -712,8 +711,7 @@ ENTRY(ext_int_handler)
        lg      %r12,__LC_THREAD_INFO
        larl    %r13,cleanup_critical
        lmg     %r8,%r9,__LC_EXT_OLD_PSW
-       SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_STACK,STACK_SHIFT,\
-                    __LC_ASYNC_ENTER_TIMER
+       SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_ENTER_TIMER
        stmg    %r0,%r7,__PT_R0(%r11)
        mvc     __PT_R8(64,%r11),__LC_SAVE_AREA_ASYNC
        stmg    %r8,%r9,__PT_PSW(%r11)
@@ -892,8 +890,7 @@ ENTRY(mcck_int_handler)
        mvc     __LC_MCCK_ENTER_TIMER(8),0(%r14)
 3:     tm      __LC_MCCK_CODE+2,0x09   # mwp + ia of old psw valid?
        jno     .Lmcck_panic            # no -> skip cleanup critical
-       SWITCH_ASYNC __LC_GPREGS_SAVE_AREA+64,__LC_PANIC_STACK,PAGE_SHIFT,\
-                    __LC_MCCK_ENTER_TIMER
+       SWITCH_ASYNC __LC_GPREGS_SAVE_AREA+64,__LC_MCCK_ENTER_TIMER
 .Lmcck_skip:
        lghi    %r14,__LC_GPREGS_SAVE_AREA+64
        stmg    %r0,%r7,__PT_R0(%r11)
@@ -928,12 +925,8 @@ ENTRY(mcck_int_handler)
        lpswe   __LC_RETURN_MCCK_PSW
 
 .Lmcck_panic:
-       lg      %r14,__LC_PANIC_STACK
-       slgr    %r14,%r15
-       srag    %r14,%r14,PAGE_SHIFT
-       jz      0f
        lg      %r15,__LC_PANIC_STACK
-0:     aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
+       aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
        j       .Lmcck_skip
 
 #