Commit 4416d2ed authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

s390/mm,fault: use static key for store indication 



Generate slightly better code by using a static key to implement store
indication. This allows to get rid of a memory access on the hot path.

Reviewed-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 9641613f

arch/s390/mm/fault.c

+7 −4
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/signal.h>

#include <linux/sched.h>

#include <linux/sched/debug.h>

#include <linux/jump_label.h>

#include <linux/kernel.h>

#include <linux/errno.h>

#include <linux/string.h>
@@ -60,12 +61,12 @@ enum fault_type { 
	GMAP_FAULT,

};



static unsigned long store_indication __read_mostly;

static DEFINE_STATIC_KEY_FALSE(have_store_indication);



static int __init fault_init(void)

{

	if (test_facility(75))

		store_indication = 0xc00;

		static_branch_enable(&have_store_indication);

	return 0;

}

early_initcall(fault_init);
@@ -104,11 +105,13 @@ static unsigned long get_fault_address(struct pt_regs *regs) 
	return trans_exc_code & __FAIL_ADDR_MASK;

}



static bool fault_is_write(struct pt_regs *regs)

static __always_inline bool fault_is_write(struct pt_regs *regs)

{

	unsigned long trans_exc_code = regs->int_parm_long;



	return (trans_exc_code & store_indication) == 0x400;

	if (static_branch_likely(&have_store_indication))

		return (trans_exc_code & 0xc00) == 0x400;

	return false;

}



static int bad_address(void *p)