s390/kernel: squeeze a few more cycles out of the system call handler

Reorder the instructions of UPDATE_VTIME to improve superscalar execution,
remove duplicate checks for problem-state from the asynchronous interrupt
handlers, and move the check for problem-state from the synchronous
exit path to the program check path as it is only needed for program
checks inside the kernel.

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

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 9406e7a62d2fd6fa48277d1b2e9406612eb7131b..a721c39d014d0729163083145235b98db09e996d 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
+       .macro  SWITCH_ASYNC savearea,stack,shift,timer
        tmhh    %r8,0x0001              # interrupting from user ?
        jnz     1f
        lgr     %r14,%r9
@@ -97,23 +97,25 @@ _PIF_WORK   = (_PIF_PER_TRAP)
 0:     lg      %r14,\stack             # are we already on the target stack?
        slgr    %r14,%r15
        srag    %r14,%r14,\shift
-       jnz     1f
+       jnz     2f
        CHECK_STACK 1<<\shift,\savearea
        aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
-       j       2f
-1:     lg      %r15,\stack             # load target stack
-2:     la      %r11,STACK_FRAME_OVERHEAD(%r15)
+       j       3f
+1:     LAST_BREAK %r14
+       UPDATE_VTIME %r14,%r15,\timer
+2:     lg      %r15,\stack             # load target stack
+3:     la      %r11,STACK_FRAME_OVERHEAD(%r15)
        .endm
 
-       .macro UPDATE_VTIME scratch,enter_timer
-       lg      \scratch,__LC_EXIT_TIMER
-       slg     \scratch,\enter_timer
-       alg     \scratch,__LC_USER_TIMER
-       stg     \scratch,__LC_USER_TIMER
-       lg      \scratch,__LC_LAST_UPDATE_TIMER
-       slg     \scratch,__LC_EXIT_TIMER
-       alg     \scratch,__LC_SYSTEM_TIMER
-       stg     \scratch,__LC_SYSTEM_TIMER
+       .macro UPDATE_VTIME w1,w2,enter_timer
+       lg      \w1,__LC_EXIT_TIMER
+       lg      \w2,__LC_LAST_UPDATE_TIMER
+       slg     \w1,\enter_timer
+       slg     \w2,__LC_EXIT_TIMER
+       alg     \w1,__LC_USER_TIMER
+       alg     \w2,__LC_SYSTEM_TIMER
+       stg     \w1,__LC_USER_TIMER
+       stg     \w2,__LC_SYSTEM_TIMER
        mvc     __LC_LAST_UPDATE_TIMER(8),\enter_timer
        .endm
 
@@ -246,9 +248,9 @@ ENTRY(system_call)
 .Lsysc_per:
        lg      %r15,__LC_KERNEL_STACK
        la      %r11,STACK_FRAME_OVERHEAD(%r15) # pointer to pt_regs
-.Lsysc_vtime:
-       UPDATE_VTIME %r13,__LC_SYNC_ENTER_TIMER
        LAST_BREAK %r13
+.Lsysc_vtime:
+       UPDATE_VTIME %r10,%r13,__LC_SYNC_ENTER_TIMER
        stmg    %r0,%r7,__PT_R0(%r11)
        mvc     __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC
        mvc     __PT_PSW(16,%r11),__LC_SVC_OLD_PSW
@@ -278,8 +280,6 @@ ENTRY(system_call)
 .Lsysc_return:
        LOCKDEP_SYS_EXIT
 .Lsysc_tif:
-       tm      __PT_PSW+1(%r11),0x01           # returning to user ?
-       jno     .Lsysc_restore
        tm      __PT_FLAGS+7(%r11),_PIF_WORK
        jnz     .Lsysc_work
        tm      __TI_flags+7(%r12),_TIF_WORK
@@ -467,8 +467,8 @@ ENTRY(pgm_check_handler)
 1:     CHECK_STACK STACK_SIZE,__LC_SAVE_AREA_SYNC
        aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
        j       3f
-2:     UPDATE_VTIME %r14,__LC_SYNC_ENTER_TIMER
-       LAST_BREAK %r14
+2:     LAST_BREAK %r14
+       UPDATE_VTIME %r14,%r15,__LC_SYNC_ENTER_TIMER
        lg      %r15,__LC_KERNEL_STACK
        lg      %r14,__TI_task(%r12)
        aghi    %r14,__TASK_thread      # pointer to thread_struct
@@ -498,11 +498,15 @@ ENTRY(pgm_check_handler)
        llgh    %r10,__PT_INT_CODE+2(%r11)
        nill    %r10,0x007f
        sll     %r10,2
-       je      .Lsysc_return
+       je      .Lpgm_return
        lgf     %r1,0(%r10,%r1)         # load address of handler routine
        lgr     %r2,%r11                # pass pointer to pt_regs
        basr    %r14,%r1                # branch to interrupt-handler
-       j       .Lsysc_return
+.Lpgm_return:
+       LOCKDEP_SYS_EXIT
+       tm      __PT_PSW+1(%r11),0x01   # returning to user ?
+       jno     .Lsysc_restore
+       j       .Lsysc_tif
 
 #
 # PER event in supervisor state, must be kprobes
@@ -512,7 +516,7 @@ ENTRY(pgm_check_handler)
        xc      __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
        lgr     %r2,%r11                # pass pointer to pt_regs
        brasl   %r14,do_per_trap
-       j       .Lsysc_return
+       j       .Lpgm_return
 
 #
 # single stepped system call
@@ -535,12 +539,8 @@ 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
-       tmhh    %r8,0x0001              # interrupting from user?
-       jz      .Lio_skip
-       UPDATE_VTIME %r14,__LC_ASYNC_ENTER_TIMER
-       LAST_BREAK %r14
-.Lio_skip:
+       SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_STACK,STACK_SHIFT,\
+                    __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)
@@ -712,12 +712,8 @@ 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
-       tmhh    %r8,0x0001              # interrupting from user ?
-       jz      .Lext_skip
-       UPDATE_VTIME %r14,__LC_ASYNC_ENTER_TIMER
-       LAST_BREAK %r14
-.Lext_skip:
+       SWITCH_ASYNC __LC_SAVE_AREA_ASYNC,__LC_ASYNC_STACK,STACK_SHIFT,\
+                    __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)
@@ -896,11 +892,8 @@ 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
-       tm      %r8,0x0001              # interrupting from user ?
-       jz      .Lmcck_skip
-       UPDATE_VTIME %r14,__LC_MCCK_ENTER_TIMER
-       LAST_BREAK %r14
+       SWITCH_ASYNC __LC_GPREGS_SAVE_AREA+64,__LC_PANIC_STACK,PAGE_SHIFT,\
+                    __LC_MCCK_ENTER_TIMER
 .Lmcck_skip:
        lghi    %r14,__LC_GPREGS_SAVE_AREA+64
        stmg    %r0,%r7,__PT_R0(%r11)
@@ -1125,7 +1118,7 @@ cleanup_critical:
        .quad   system_call
        .quad   .Lsysc_stmg
        .quad   .Lsysc_per
-       .quad   .Lsysc_vtime+18
+       .quad   .Lsysc_vtime+36
        .quad   .Lsysc_vtime+42
 
 .Lcleanup_sysc_tif: