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s390: Add support for DCACHE_WORD_ACCESS (again)

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Implement load_unaligned_zeropad() and enable DCACHE_WORD_ACCESS to
speed up string operations in fs/dcache.c and fs/namei.c.

With the secure storage access exception cases addressed, add support
for DCACHE_WORD_ACCESS again.

Tested-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens
2026-07-20 10:58:34 +02:00
committed by Vasily Gorbik
parent e462200886
commit 656db30220
4 changed files with 45 additions and 0 deletions
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1
arch/s390/Kconfig
View File

@@ -166,6 +166,7 @@ config S390
select ARCH_WANTS_THP_SWAP
select BUILDTIME_TABLE_SORT
select CLONE_BACKWARDS2
select DCACHE_WORD_ACCESS if !KMSAN
select DYNAMIC_FTRACE if FUNCTION_TRACER
select FUNCTION_ALIGNMENT_8B if CC_IS_GCC
select FUNCTION_ALIGNMENT_16B if !CC_IS_GCC

4
arch/s390/include/asm/asm-extable.h
View File

@@ -12,6 +12,7 @@
#define EX_TYPE_UA_FAULT 3
#define EX_TYPE_UA_LOAD_REG 5
#define EX_TYPE_UA_LOAD_REGPAIR 6
#define EX_TYPE_ZEROPAD 7
#define EX_TYPE_FPC 8
#define EX_TYPE_UA_MVCOS_TO 9
#define EX_TYPE_UA_MVCOS_FROM 10
@@ -79,6 +80,9 @@
#define EX_TABLE_UA_LOAD_REGPAIR(_fault, _target, _regerr, _regzero) \
__EX_TABLE(__ex_table, _fault, _target, EX_TYPE_UA_LOAD_REGPAIR, _regerr, _regzero, 0)
#define EX_TABLE_ZEROPAD(_fault, _target, _regdata, _regaddr) \
__EX_TABLE(__ex_table, _fault, _target, EX_TYPE_ZEROPAD, _regdata, _regaddr, 0)
#define EX_TABLE_FPC(_fault, _target) \
__EX_TABLE(__ex_table, _fault, _target, EX_TYPE_FPC, __stringify(%%r0), __stringify(%%r0), 0)

22
arch/s390/include/asm/word-at-a-time.h
View File

@@ -4,6 +4,7 @@
#include <linux/bitops.h>
#include <linux/wordpart.h>
#include <asm/asm-extable.h>
#include <asm/bitsperlong.h>
struct word_at_a_time {
@@ -40,4 +41,25 @@ static inline unsigned long zero_bytemask(unsigned long data)
return ~1UL << data;
}
/*
* Load an unaligned word from kernel space.
*
* In the (very unlikely) case of the word being a page-crosser
* and the next page not being mapped, take the exception and
* return zeroes in the non-existing part.
*/
static inline unsigned long load_unaligned_zeropad(const void *addr)
{
unsigned long data;
asm_inline volatile(
"0: lg %[data],0(%[addr])\n"
"1: nopr %%r7\n"
EX_TABLE_ZEROPAD(0b, 1b, %[data], %[addr])
EX_TABLE_ZEROPAD(1b, 1b, %[data], %[addr])
: [data] "=d" (data)
: [addr] "a" (addr), "m" (*(unsigned long *)addr));
return data;
}
#endif /* _ASM_WORD_AT_A_TIME_H */

18
arch/s390/mm/extable.c
View File

@@ -50,6 +50,22 @@ static bool ex_handler_ua_load_reg(const struct exception_table_entry *ex,
return true;
}
static bool ex_handler_zeropad(const struct exception_table_entry *ex, struct pt_regs *regs)
{
unsigned int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data);
unsigned int reg_data = FIELD_GET(EX_DATA_REG_ERR, ex->data);
unsigned long data, addr, offset;
addr = regs->gprs[reg_addr];
offset = addr & (sizeof(unsigned long) - 1);
addr &= ~(sizeof(unsigned long) - 1);
data = *(unsigned long *)addr;
data <<= BITS_PER_BYTE * offset;
regs->gprs[reg_data] = data;
regs->psw.addr = extable_fixup(ex);
return true;
}
static bool ex_handler_fpc(const struct exception_table_entry *ex, struct pt_regs *regs)
{
fpu_sfpc(0);
@@ -118,6 +134,8 @@ bool fixup_exception(struct pt_regs *regs)
return ex_handler_ua_load_reg(ex, false, regs);
case EX_TYPE_UA_LOAD_REGPAIR:
return ex_handler_ua_load_reg(ex, true, regs);
case EX_TYPE_ZEROPAD:
return ex_handler_zeropad(ex, regs);
case EX_TYPE_FPC:
return ex_handler_fpc(ex, regs);
case EX_TYPE_UA_MVCOS_TO: