[S390] s390: Optimize user and work TIF check
On return from syscall or interrupt, we have to check if we return to userspace (likely) and if there is work todo (less likely) to decide if we handle the work. We can optimize this check: we first check for the less likely work case and then check for userspace. This patch is also a preparation for an additional patch, that fixes a bug in KVM dealing with cpu bound guests. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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@ -279,8 +279,6 @@ sysc_do_restart:
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st %r2,SP_R2(%r15) # store return value (change R2 on stack)
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sysc_return:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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bno BASED(sysc_restore)
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tm __TI_flags+3(%r9),_TIF_WORK_SVC
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bnz BASED(sysc_work) # there is work to do (signals etc.)
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sysc_restore:
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@ -312,6 +310,8 @@ sysc_work_loop:
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# One of the work bits is on. Find out which one.
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#
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sysc_work:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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bno BASED(sysc_restore)
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tm __TI_flags+3(%r9),_TIF_MCCK_PENDING
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bo BASED(sysc_mcck_pending)
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tm __TI_flags+3(%r9),_TIF_NEED_RESCHED
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@ -602,12 +602,6 @@ io_no_vtime:
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la %r2,SP_PTREGS(%r15) # address of register-save area
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basr %r14,%r1 # branch to standard irq handler
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io_return:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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#ifdef CONFIG_PREEMPT
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bno BASED(io_preempt) # no -> check for preemptive scheduling
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#else
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bno BASED(io_restore) # no-> skip resched & signal
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#endif
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tm __TI_flags+3(%r9),_TIF_WORK_INT
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bnz BASED(io_work) # there is work to do (signals etc.)
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io_restore:
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@ -629,10 +623,18 @@ io_restore_trace_psw:
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.long 0, io_restore_trace + 0x80000000
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#endif
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#ifdef CONFIG_PREEMPT
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io_preempt:
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#
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# switch to kernel stack, then check the TIF bits
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#
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io_work:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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#ifndef CONFIG_PREEMPT
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bno BASED(io_restore) # no-> skip resched & signal
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#else
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bnz BASED(io_work_user) # no -> check for preemptive scheduling
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# check for preemptive scheduling
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icm %r0,15,__TI_precount(%r9)
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bnz BASED(io_restore)
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bnz BASED(io_restore) # preemption disabled
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l %r1,SP_R15(%r15)
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s %r1,BASED(.Lc_spsize)
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mvc SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
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@ -646,10 +648,7 @@ io_resume_loop:
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br %r1 # call schedule
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#endif
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#
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# switch to kernel stack, then check the TIF bits
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#
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io_work:
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io_work_user:
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l %r1,__LC_KERNEL_STACK
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s %r1,BASED(.Lc_spsize)
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mvc SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
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@ -271,8 +271,6 @@ sysc_noemu:
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stg %r2,SP_R2(%r15) # store return value (change R2 on stack)
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sysc_return:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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jno sysc_restore
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tm __TI_flags+7(%r9),_TIF_WORK_SVC
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jnz sysc_work # there is work to do (signals etc.)
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sysc_restore:
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@ -304,6 +302,8 @@ sysc_work_loop:
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# One of the work bits is on. Find out which one.
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#
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sysc_work:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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jno sysc_restore
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tm __TI_flags+7(%r9),_TIF_MCCK_PENDING
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jo sysc_mcck_pending
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tm __TI_flags+7(%r9),_TIF_NEED_RESCHED
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@ -585,12 +585,6 @@ io_no_vtime:
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la %r2,SP_PTREGS(%r15) # address of register-save area
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brasl %r14,do_IRQ # call standard irq handler
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io_return:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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#ifdef CONFIG_PREEMPT
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jno io_preempt # no -> check for preemptive scheduling
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#else
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jno io_restore # no-> skip resched & signal
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#endif
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tm __TI_flags+7(%r9),_TIF_WORK_INT
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jnz io_work # there is work to do (signals etc.)
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io_restore:
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@ -612,10 +606,18 @@ io_restore_trace_psw:
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.quad 0, io_restore_trace
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#endif
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#ifdef CONFIG_PREEMPT
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io_preempt:
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#
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# switch to kernel stack, then check TIF bits
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#
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io_work:
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tm SP_PSW+1(%r15),0x01 # returning to user ?
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#ifndef CONFIG_PREEMPT
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jno io_restore # no-> skip resched & signal
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#else
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jnz io_work_user # yes -> do resched & signal
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# check for preemptive scheduling
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icm %r0,15,__TI_precount(%r9)
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jnz io_restore
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jnz io_restore # preemption is disabled
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# switch to kernel stack
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lg %r1,SP_R15(%r15)
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aghi %r1,-SP_SIZE
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@ -629,10 +631,7 @@ io_resume_loop:
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jg preempt_schedule_irq
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#endif
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#
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# switch to kernel stack, then check TIF bits
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#
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io_work:
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io_work_user:
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lg %r1,__LC_KERNEL_STACK
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aghi %r1,-SP_SIZE
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mvc SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
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