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

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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: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2023-10-12 09:40:41 +02:00 committed by Vasily Gorbik
parent 9641613f48
commit 4416d2ed81
1 changed files with 7 additions and 4 deletions
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11
arch/s390/mm/fault.c
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@ -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)