[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/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