[S390] rework idle code
Whenever the cpu loads an enabled wait PSW it will appear as idle to the
underlying host system. The code in default_idle calls vtime_stop_cpu
which does the necessary voodoo to get the cpu time accounting right.
The udelay code just loads an enabled wait PSW. To correct this rework
the vtime_stop_cpu/vtime_start_cpu logic and move the difficult parts
to entry[64].S, vtime_stop_cpu can now be called from anywhere and
vtime_start_cpu is gone. The correction of the cpu time during wakeup
from an enabled wait PSW is done with a critical section in entry[64].S.
As vtime_start_cpu is gone, s390_idle_check can be removed as well.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 6143521..74ee563 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -105,14 +105,14 @@
.macro ADD64 high,low,timer
al \high,\timer
- al \low,\timer+4
+ al \low,4+\timer
brc 12,.+8
ahi \high,1
.endm
.macro SUB64 high,low,timer
sl \high,\timer
- sl \low,\timer+4
+ sl \low,4+\timer
brc 3,.+8
ahi \high,-1
.endm
@@ -471,7 +471,6 @@
jnz io_work # there is work to do (signals etc.)
io_restore:
mvc __LC_RETURN_PSW(8),__PT_PSW(%r11)
- ni __LC_RETURN_PSW+1,0xfd # clean wait state bit
stpt __LC_EXIT_TIMER
lm %r0,%r15,__PT_R0(%r11)
lpsw __LC_RETURN_PSW
@@ -612,6 +611,26 @@
basr %r14,%r1 # call do_extint
j io_return
+/*
+ * Load idle PSW. The second "half" of this function is in cleanup_idle.
+ */
+ENTRY(psw_idle)
+ st %r4,__SF_EMPTY(%r15)
+ basr %r1,0
+ la %r1,psw_idle_lpsw+4-.(%r1)
+ st %r1,__SF_EMPTY+4(%r15)
+ oi __SF_EMPTY+4(%r15),0x80
+ la %r1,.Lvtimer_max-psw_idle_lpsw-4(%r1)
+ stck __IDLE_ENTER(%r2)
+ ltr %r5,%r5
+ stpt __VQ_IDLE_ENTER(%r3)
+ jz psw_idle_lpsw
+ spt 0(%r1)
+psw_idle_lpsw:
+ lpsw __SF_EMPTY(%r15)
+ br %r14
+psw_idle_end:
+
__critical_end:
/*
@@ -673,7 +692,6 @@
TRACE_IRQS_ON
mcck_return:
mvc __LC_RETURN_MCCK_PSW(8),__PT_PSW(%r11) # move return PSW
- ni __LC_RETURN_MCCK_PSW+1,0xfd # clear wait state bit
tm __LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?
jno 0f
lm %r0,%r15,__PT_R0(%r11)
@@ -748,6 +766,8 @@
.long io_tif + 0x80000000
.long io_restore + 0x80000000
.long io_done + 0x80000000
+ .long psw_idle + 0x80000000
+ .long psw_idle_end + 0x80000000
cleanup_critical:
cl %r9,BASED(cleanup_table) # system_call
@@ -766,6 +786,10 @@
jl cleanup_io_tif
cl %r9,BASED(cleanup_table+28) # io_done
jl cleanup_io_restore
+ cl %r9,BASED(cleanup_table+32) # psw_idle
+ jl 0f
+ cl %r9,BASED(cleanup_table+36) # psw_idle_end
+ jl cleanup_idle
0: br %r14
cleanup_system_call:
@@ -849,7 +873,6 @@
jhe 0f
l %r9,12(%r11) # get saved r11 pointer to pt_regs
mvc __LC_RETURN_PSW(8),__PT_PSW(%r9)
- ni __LC_RETURN_PSW+1,0xfd # clear wait state bit
mvc 0(32,%r11),__PT_R8(%r9)
lm %r0,%r7,__PT_R0(%r9)
0: lm %r8,%r9,__LC_RETURN_PSW
@@ -857,11 +880,52 @@
cleanup_io_restore_insn:
.long io_done - 4 + 0x80000000
+cleanup_idle:
+ # copy interrupt clock & cpu timer
+ mvc __IDLE_EXIT(8,%r2),__LC_INT_CLOCK
+ mvc __VQ_IDLE_EXIT(8,%r3),__LC_ASYNC_ENTER_TIMER
+ chi %r11,__LC_SAVE_AREA_ASYNC
+ je 0f
+ mvc __IDLE_EXIT(8,%r2),__LC_MCCK_CLOCK
+ mvc __VQ_IDLE_EXIT(8,%r3),__LC_MCCK_ENTER_TIMER
+0: # check if stck has been executed
+ cl %r9,BASED(cleanup_idle_insn)
+ jhe 1f
+ mvc __IDLE_ENTER(8,%r2),__IDLE_EXIT(%r2)
+ mvc __VQ_IDLE_ENTER(8,%r3),__VQ_IDLE_EXIT(%r3)
+ j 2f
+1: # check if the cpu timer has been reprogrammed
+ ltr %r5,%r5
+ jz 2f
+ spt __VQ_IDLE_ENTER(%r3)
+2: # account system time going idle
+ lm %r9,%r10,__LC_STEAL_TIMER
+ ADD64 %r9,%r10,__IDLE_ENTER(%r2)
+ SUB64 %r9,%r10,__LC_LAST_UPDATE_CLOCK
+ stm %r9,%r10,__LC_STEAL_TIMER
+ mvc __LC_LAST_UPDATE_CLOCK(8),__IDLE_EXIT(%r2)
+ lm %r9,%r10,__LC_SYSTEM_TIMER
+ ADD64 %r9,%r10,__LC_LAST_UPDATE_TIMER
+ SUB64 %r9,%r10,__VQ_IDLE_ENTER(%r3)
+ stm %r9,%r10,__LC_SYSTEM_TIMER
+ mvc __LC_LAST_UPDATE_TIMER(8),__VQ_IDLE_EXIT(%r3)
+ # prepare return psw
+ n %r8,BASED(cleanup_idle_wait) # clear wait state bit
+ l %r9,24(%r11) # return from psw_idle
+ br %r14
+cleanup_idle_insn:
+ .long psw_idle_lpsw + 0x80000000
+cleanup_idle_wait:
+ .long 0xfffdffff
+
/*
* Integer constants
*/
.align 4
-.Lnr_syscalls: .long NR_syscalls
+.Lnr_syscalls:
+ .long NR_syscalls
+.Lvtimer_max:
+ .quad 0x7fffffffffffffff
/*
* Symbol constants