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s390/uaccess: get rid of indirect function calls

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There are only two uaccess variants on s390 left: the version that is used
if the mvcos instruction is available, and the page table walk variant.
So there is no need for expensive indirect function calls.

By default the mvcos variant will be called. If the mvcos instruction is not
available it will call the page table walk variant.

For minimal performance impact the "if (mvcos_is_available)" is implemented
with a jump label, which will be a six byte nop on machines with mvcos.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2014-01-23 11:18:36 +01:00 • committed by Martin Schwidefsky
parent cfa785e623
commit 4f41c2b456
7 changed files with 152 additions and 149 deletions
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9
arch/s390/kernel/setup.c
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@ -47,7 +47,6 @@
#include <linux/compat.h>
#include <asm/ipl.h>
#include <asm/uaccess.h>
#include <asm/facility.h>
#include <asm/smp.h>
#include <asm/mmu_context.h>
@ -64,12 +63,6 @@
#include <asm/sclp.h>
#include "entry.h"
/*
* User copy operations.
*/
struct uaccess_ops uaccess;
EXPORT_SYMBOL(uaccess);
/*
* Machine setup..
*/
@ -1009,8 +1002,6 @@ void __init setup_arch(char **cmdline_p)
init_mm.end_data = (unsigned long) &_edata;
init_mm.brk = (unsigned long) &_end;
uaccess = MACHINE_HAS_MVCOS ? uaccess_mvcos : uaccess_pt;
parse_early_param();
detect_memory_layout(memory_chunk, memory_end);
os_info_init();