s390/vtimer: rework virtual timer interface

The current virtual timer interface is inherently per-cpu and hard to
use. The sole user of the interface is appldata which uses it to execute
a function after a specific amount of cputime has been used over all cpus.

Rework the virtual timer interface to hook into the cputime accounting.
This makes the interface independent from the CPU timer interrupts, and
makes the virtual timers global as opposed to per-cpu.
Overall the code is greatly simplified. The downside is that the accuracy
is not as good as the original implementation, but it is still good enough
for appldata.

Reviewed-by: Jan Glauber <jang@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 14 insertions, 23 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 2c0eff488875..870bad6d56fc 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -616,17 +616,13 @@ ext_skip:
  * Load idle PSW. The second "half" of this function is in cleanup_idle.
  */
 ENTRY(psw_idle)
-        st      %r4,__SF_EMPTY(%r15)
+        st      %r3,__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)
+        stck    __CLOCK_IDLE_ENTER(%r2)
+        stpt    __TIMER_IDLE_ENTER(%r2)
 psw_idle_lpsw:
         lpsw    __SF_EMPTY(%r15)
         br      %r14
@@ -885,33 +881,28 @@ cleanup_io_restore_insn:
 
 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
+        mvc     __CLOCK_IDLE_EXIT(8,%r2),__LC_INT_CLOCK
+        mvc     __TIMER_IDLE_EXIT(8,%r2),__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
+        mvc     __CLOCK_IDLE_EXIT(8,%r2),__LC_MCCK_CLOCK
+        mvc     __TIMER_IDLE_EXIT(8,%r2),__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
+        mvc     __CLOCK_IDLE_ENTER(8,%r2),__CLOCK_IDLE_EXIT(%r2)
+        mvc     __TIMER_IDLE_ENTER(8,%r2),__TIMER_IDLE_EXIT(%r3)
+1:      # account system time going idle
         lm      %r9,%r10,__LC_STEAL_TIMER
-        ADD64   %r9,%r10,__IDLE_ENTER(%r2)
+        ADD64   %r9,%r10,__CLOCK_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)
+        mvc     __LC_LAST_UPDATE_CLOCK(8),__CLOCK_IDLE_EXIT(%r2)
         lm      %r9,%r10,__LC_SYSTEM_TIMER
         ADD64   %r9,%r10,__LC_LAST_UPDATE_TIMER
-        SUB64   %r9,%r10,__VQ_IDLE_ENTER(%r3)
+        SUB64   %r9,%r10,__TIMER_IDLE_ENTER(%r2)
         stm     %r9,%r10,__LC_SYSTEM_TIMER
-        mvc     __LC_LAST_UPDATE_TIMER(8),__VQ_IDLE_EXIT(%r3)
+        mvc     __LC_LAST_UPDATE_TIMER(8),__TIMER_IDLE_EXIT(%r2)
         # prepare return psw
         n       %r8,BASED(cleanup_idle_wait)    # clear wait state bit
         l       %r9,24(%r11)                    # return from psw_idle