[S390] cleanup sysc_work and io_work code

Cleanup the #ifdef mess at io_work in entry[64].S and streamline the
TIF work code of the system call and io exit path.

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

1 files changed, 36 insertions, 72 deletions

diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 52106d53271c..ca02b10a2c32 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -291,38 +291,36 @@ sysc_restore_trace_psw:
 #endif
 
 #
-# recheck if there is more work to do
-#
-sysc_work_loop:
-        tm      __TI_flags+7(%r9),_TIF_WORK_SVC
-        jz      sysc_restore      # there is no work to do
-#
-# One of the work bits is on. Find out which one.
+# There is work to do, but first we need to check if we return to userspace.
 #
 sysc_work:
         tm      SP_PSW+1(%r15),0x01     # returning to user ?
         jno     sysc_restore
+
+#
+# One of the work bits is on. Find out which one.
+#
+sysc_work_loop:
         tm      __TI_flags+7(%r9),_TIF_MCCK_PENDING
         jo      sysc_mcck_pending
         tm      __TI_flags+7(%r9),_TIF_NEED_RESCHED
         jo      sysc_reschedule
         tm      __TI_flags+7(%r9),_TIF_SIGPENDING
-        jnz     sysc_sigpending
+        jo      sysc_sigpending
         tm      __TI_flags+7(%r9),_TIF_NOTIFY_RESUME
-        jnz     sysc_notify_resume
+        jo      sysc_notify_resume
         tm      __TI_flags+7(%r9),_TIF_RESTART_SVC
         jo      sysc_restart
         tm      __TI_flags+7(%r9),_TIF_SINGLE_STEP
         jo      sysc_singlestep
-        j       sysc_restore
-sysc_work_done:
+        j       sysc_return             # beware of critical section cleanup
 
 #
 # _TIF_NEED_RESCHED is set, call schedule
 #
 sysc_reschedule:
         larl    %r14,sysc_work_loop
-        jg      schedule        # return point is sysc_return
+        jg      schedule                # return point is sysc_work_loop
 
 #
 # _TIF_MCCK_PENDING is set, call handler
@@ -369,7 +367,7 @@ sysc_singlestep:
         ni      __TI_flags+7(%r9),255-_TIF_SINGLE_STEP  # clear TIF_SINGLE_STEP
         xc      SP_SVCNR(2,%r15),SP_SVCNR(%r15)         # clear svc number
         la      %r2,SP_PTREGS(%r15)     # address of register-save area
-        larl    %r14,sysc_return        # load adr. of system return
+        larl    %r14,sysc_work_loop     # load adr. of system return
         jg      do_single_step          # branch to do_sigtrap
 
 #
@@ -605,37 +603,27 @@ io_restore_trace_psw:
 #endif
 
 #
-# There is work todo, we need to check if we return to userspace, then
-# check, if we are in SIE, if yes leave it
+# There is work todo, find out in which context we have been interrupted:
+# 1) if we return to user space we can do all _TIF_WORK_INT work
+# 2) if we return to kernel code and kvm is enabled check if we need to
+#    modify the psw to leave SIE
+# 3) if we return to kernel code and preemptive scheduling is enabled check
+#    the preemption counter and if it is zero call preempt_schedule_irq
+# Before any work can be done, a switch to the kernel stack is required.
 #
 io_work:
         tm      SP_PSW+1(%r15),0x01     # returning to user ?
-#ifndef CONFIG_PREEMPT
-#if defined(CONFIG_KVM) || defined(CONFIG_KVM_MODULE)
-        jnz     io_work_user            # yes -> no need to check for SIE
-        la      %r1, BASED(sie_opcode)  # we return to kernel here
-        lg      %r2, SP_PSW+8(%r15)
-        clc     0(2,%r1), 0(%r2)        # is current instruction = SIE?
-        jne     io_restore              # no-> return to kernel
-        lg      %r1, SP_PSW+8(%r15)     # yes-> add 4 bytes to leave SIE
-        aghi    %r1, 4
-        stg     %r1, SP_PSW+8(%r15)
-        j       io_restore              # return to kernel
-#else
-        jno     io_restore              # no-> skip resched & signal
-#endif
-#else
-        jnz     io_work_user            # yes -> do resched & signal
+        jo      io_work_user            # yes -> do resched & signal
 #if defined(CONFIG_KVM) || defined(CONFIG_KVM_MODULE)
-        la      %r1, BASED(sie_opcode)
-        lg      %r2, SP_PSW+8(%r15)
-        clc     0(2,%r1), 0(%r2)        # is current instruction = SIE?
+        lg      %r2,SP_PSW+8(%r15)      # check if current instruction is SIE
+        lh      %r1,0(%r2)
+        chi     %r1,-19948              # signed 16 bit compare with 0xb214
         jne     0f                      # no -> leave PSW alone
-        lg      %r1, SP_PSW+8(%r15)     # yes-> add 4 bytes to leave SIE
-        aghi    %r1, 4
-        stg     %r1, SP_PSW+8(%r15)
+        aghi    %r2,4                   # yes-> add 4 bytes to leave SIE
+        stg     %r2,SP_PSW+8(%r15)
 0:
 #endif
+#ifdef CONFIG_PREEMPT
         # check for preemptive scheduling
         icm     %r0,15,__TI_precount(%r9)
         jnz     io_restore              # preemption is disabled
@@ -646,21 +634,25 @@ io_work:
         xc      __SF_BACKCHAIN(8,%r1),__SF_BACKCHAIN(%r1) # clear back chain
         lgr     %r15,%r1
 io_resume_loop:
-        tm      __TI_flags+7(%r9),_TIF_NEED_RESCHED
-        jno     io_restore
         larl    %r14,io_resume_loop
-        jg      preempt_schedule_irq
+        tm      __TI_flags+7(%r12),_TIF_NEED_RESCHED
+        jgo     preempt_schedule_irq
 #endif
+        j       io_restore
 
+#
+# Need to do work before returning to userspace, switch to kernel stack
+#
 io_work_user:
         lg      %r1,__LC_KERNEL_STACK
         aghi    %r1,-SP_SIZE
         mvc     SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
         xc      __SF_BACKCHAIN(8,%r1),__SF_BACKCHAIN(%r1) # clear back chain
         lgr     %r15,%r1
+
 #
 # One of the work bits is on. Find out which one.
-# Checked are: _TIF_SIGPENDING, _TIF_RESTORE_SIGPENDING, _TIF_NEED_RESCHED
+# Checked are: _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_NEED_RESCHED
 #              and _TIF_MCCK_PENDING
 #
 io_work_loop:
@@ -669,16 +661,10 @@ io_work_loop:
         tm      __TI_flags+7(%r9),_TIF_NEED_RESCHED
         jo      io_reschedule
         tm      __TI_flags+7(%r9),_TIF_SIGPENDING
-        jnz     io_sigpending
+        jo      io_sigpending
         tm      __TI_flags+7(%r9),_TIF_NOTIFY_RESUME
-        jnz     io_notify_resume
-        j       io_restore
-io_work_done:
-
-#if defined(CONFIG_KVM) || defined(CONFIG_KVM_MODULE)
-sie_opcode:
-        .long 0xb2140000
-#endif
+        jo      io_notify_resume
+        j       io_return               # beware of critical section cleanup
 
 #
 # _TIF_MCCK_PENDING is set, call handler
@@ -696,8 +682,6 @@ io_reschedule:
         brasl   %r14,schedule           # call scheduler
         stnsm   __SF_EMPTY(%r15),0xfc   # disable I/O and ext. interrupts
         TRACE_IRQS_OFF
-        tm      __TI_flags+7(%r9),_TIF_WORK_INT
-        jz      io_restore              # there is no work to do
         j       io_work_loop
 
 #
@@ -903,14 +887,10 @@ cleanup_table_sysc_return:
         .quad   sysc_return, sysc_leave
 cleanup_table_sysc_leave:
         .quad   sysc_leave, sysc_done
-cleanup_table_sysc_work_loop:
-        .quad   sysc_work_loop, sysc_work_done
 cleanup_table_io_return:
         .quad   io_return, io_leave
 cleanup_table_io_leave:
         .quad   io_leave, io_done
-cleanup_table_io_work_loop:
-        .quad   io_work_loop, io_work_done
 
 cleanup_critical:
         clc     8(8,%r12),BASED(cleanup_table_system_call)
@@ -928,11 +908,6 @@ cleanup_critical:
         clc     8(8,%r12),BASED(cleanup_table_sysc_leave+8)
         jl      cleanup_sysc_leave
 0:
-        clc     8(8,%r12),BASED(cleanup_table_sysc_work_loop)
-        jl      0f
-        clc     8(8,%r12),BASED(cleanup_table_sysc_work_loop+8)
-        jl      cleanup_sysc_return
-0:
         clc     8(8,%r12),BASED(cleanup_table_io_return)
         jl      0f
         clc     8(8,%r12),BASED(cleanup_table_io_return+8)
@@ -943,11 +918,6 @@ cleanup_critical:
         clc     8(8,%r12),BASED(cleanup_table_io_leave+8)
         jl      cleanup_io_leave
 0:
-        clc     8(8,%r12),BASED(cleanup_table_io_work_loop)
-        jl      0f
-        clc     8(8,%r12),BASED(cleanup_table_io_work_loop+8)
-        jl      cleanup_io_work_loop
-0:
         br      %r14
 
 cleanup_system_call:
@@ -1025,12 +995,6 @@ cleanup_io_return:
         la      %r12,__LC_RETURN_PSW
         br      %r14
 
-cleanup_io_work_loop:
-        mvc     __LC_RETURN_PSW(8),0(%r12)
-        mvc     __LC_RETURN_PSW+8(8),BASED(cleanup_table_io_work_loop)
-        la      %r12,__LC_RETURN_PSW
-        br      %r14
-
 cleanup_io_leave:
         clc     8(8,%r12),BASED(cleanup_io_leave_insn)
         je      3f