[patch 12/16] system call optimization.

Martin Schwidefsky
2007-07-10T09:29:47Z

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From: Martin Schwidefsky <schwidefsky@de.ibm.com>

After the in-kernel system call has been remove the system call path
can be optimized. The problem state bit of the old psw is always set
between system_call and sysc_do_svc. SAVE_ALL_SVC uses this information
to avoid two instructions.

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

arch/s390/kernel/entry.S | 7 ++++++-
arch/s390/kernel/entry64.S | 7 ++++++-
2 files changed, 12 insertions(+), 2 deletions(-)

Index: quilt-2.6/arch/s390/kernel/entry64.S
===================================================================
--- quilt-2.6.orig/arch/s390/kernel/entry64.S
+++ quilt-2.6/arch/s390/kernel/entry64.S
@@ -99,6 +99,11 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_
larl %r13,system_call
.endm

+ .macro SAVE_ALL_SVC psworg,savearea
+ la %r12,\psworg
+ lg %r15,__LC_KERNEL_STACK # problem state -> load ksp
+ .endm
+
.macro SAVE_ALL_SYNC psworg,savearea
la %r12,\psworg
tm \psworg+1,0x01 # test problem state bit
@@ -207,7 +212,7 @@ system_call:
STORE_TIMER __LC_SYNC_ENTER_TIMER
sysc_saveall:
SAVE_ALL_BASE __LC_SAVE_AREA
- SAVE_ALL_SYNC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
+ SAVE_ALL_SVC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
CREATE_STACK_FRAME __LC_SVC_OLD_PSW,__LC_SAVE_AREA
llgh %r7,__LC_SVC_INT_CODE # get svc number from lowcore
#ifdef CONFIG_VIRT_CPU_ACCOUNTING
Index: quilt-2.6/arch/s390/kernel/entry.S
===================================================================
--- quilt-2.6.orig/arch/s390/kernel/entry.S
+++ quilt-2.6/arch/s390/kernel/entry.S
@@ -107,6 +107,11 @@ STACK_SIZE = 1 << STACK_SHIFT
l %r13,__LC_SVC_NEW_PSW+4 # load &system_call to %r13
.endm

+ .macro SAVE_ALL_SVC psworg,savearea
+ la %r12,\psworg
+ l %r15,__LC_KERNEL_STACK # problem state -> load ksp
+ .endm
+
.macro SAVE_ALL_SYNC psworg,savearea
la %r12,\psworg
tm \psworg+1,0x01 # test problem state bit
@@ -218,7 +223,7 @@ system_call:
STORE_TIMER __LC_SYNC_ENTER_TIMER
sysc_saveall:
SAVE_ALL_BASE __LC_SAVE_AREA
- SAVE_ALL_SYNC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
+ SAVE_ALL_SVC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
CREATE_STACK_FRAME __LC_SVC_OLD_PSW,__LC_SAVE_AREA
lh %r7,0x8a # get svc number from lowcore
#ifdef CONFIG_VIRT_CPU_ACCOUNTING