Commit 2688905e authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent c0a18111

arch/s390/kernel/entry.S

+14 −15
Original line number Diff line number Diff line
@@ -279,8 +279,6 @@ sysc_do_restart: 
	st	%r2,SP_R2(%r15)   # store return value (change R2 on stack)



sysc_return:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

	bno	BASED(sysc_restore)

	tm	__TI_flags+3(%r9),_TIF_WORK_SVC

	bnz	BASED(sysc_work)  # there is work to do (signals etc.)

sysc_restore:
@@ -312,6 +310,8 @@ sysc_work_loop: 
# One of the work bits is on. Find out which one.

#

sysc_work:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

	bno	BASED(sysc_restore)

	tm	__TI_flags+3(%r9),_TIF_MCCK_PENDING

	bo	BASED(sysc_mcck_pending)

	tm	__TI_flags+3(%r9),_TIF_NEED_RESCHED
@@ -602,12 +602,6 @@ io_no_vtime: 
	la	%r2,SP_PTREGS(%r15)	# address of register-save area

	basr	%r14,%r1		# branch to standard irq handler

io_return:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

#ifdef CONFIG_PREEMPT

	bno	BASED(io_preempt)	# no -> check for preemptive scheduling

#else

	bno	BASED(io_restore)	# no-> skip resched & signal

#endif

	tm	__TI_flags+3(%r9),_TIF_WORK_INT

	bnz	BASED(io_work)		# there is work to do (signals etc.)

io_restore:
@@ -629,10 +623,18 @@ io_restore_trace_psw: 
	.long	0, io_restore_trace + 0x80000000

#endif



#ifdef CONFIG_PREEMPT

io_preempt:

#

# switch to kernel stack, then check the TIF bits

#

io_work:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

#ifndef CONFIG_PREEMPT

	bno	BASED(io_restore)	# no-> skip resched & signal

#else

	bnz	BASED(io_work_user)	# no -> check for preemptive scheduling

	# check for preemptive scheduling

	icm	%r0,15,__TI_precount(%r9)

	bnz	BASED(io_restore)

	bnz	BASED(io_restore)	# preemption disabled

	l	%r1,SP_R15(%r15)

	s	%r1,BASED(.Lc_spsize)

	mvc	SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
@@ -646,10 +648,7 @@ io_resume_loop: 
	br	%r1			# call schedule

#endif



#

# switch to kernel stack, then check the TIF bits

#

io_work:

io_work_user:

	l	%r1,__LC_KERNEL_STACK

	s	%r1,BASED(.Lc_spsize)

	mvc	SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)

arch/s390/kernel/entry64.S

+14 −15
Original line number Diff line number Diff line
@@ -271,8 +271,6 @@ sysc_noemu: 
	stg	%r2,SP_R2(%r15) # store return value (change R2 on stack)



sysc_return:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

	jno	sysc_restore

	tm	__TI_flags+7(%r9),_TIF_WORK_SVC

	jnz	sysc_work	# there is work to do (signals etc.)

sysc_restore:
@@ -304,6 +302,8 @@ sysc_work_loop: 
# One of the work bits is on. Find out which one.

#

sysc_work:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

	jno	sysc_restore

	tm	__TI_flags+7(%r9),_TIF_MCCK_PENDING

	jo	sysc_mcck_pending

	tm	__TI_flags+7(%r9),_TIF_NEED_RESCHED
@@ -585,12 +585,6 @@ io_no_vtime: 
	la	%r2,SP_PTREGS(%r15)	# address of register-save area

	brasl	%r14,do_IRQ		# call standard irq handler

io_return:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

#ifdef CONFIG_PREEMPT

	jno	io_preempt		# no -> check for preemptive scheduling

#else

	jno	io_restore		# no-> skip resched & signal

#endif

	tm	__TI_flags+7(%r9),_TIF_WORK_INT

	jnz	io_work 		# there is work to do (signals etc.)

io_restore:
@@ -612,10 +606,18 @@ io_restore_trace_psw: 
	.quad	0, io_restore_trace

#endif



#ifdef CONFIG_PREEMPT

io_preempt:

#

# switch to kernel stack, then check TIF bits

#

io_work:

	tm	SP_PSW+1(%r15),0x01	# returning to user ?

#ifndef CONFIG_PREEMPT

	jno	io_restore		# no-> skip resched & signal

#else

	jnz	io_work_user		# yes -> do resched & signal

	# check for preemptive scheduling

	icm	%r0,15,__TI_precount(%r9)

	jnz	io_restore

	jnz	io_restore		# preemption is disabled

	# switch to kernel stack

	lg	%r1,SP_R15(%r15)

	aghi	%r1,-SP_SIZE
@@ -629,10 +631,7 @@ io_resume_loop: 
	jg	preempt_schedule_irq

#endif



#

# switch to kernel stack, then check TIF bits

#

io_work:

io_work_user:

	lg	%r1,__LC_KERNEL_STACK

	aghi	%r1,-SP_SIZE

	mvc	SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)

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