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s390/jump_label: replace stop_machine with smp_call_function

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The use of stop_machine to replace the mask bits of the jump label branch
is a very heavy-weight operation. This is in fact not necessary, the
mask of the branch can simply be updated, followed by a signal processor
to all the other CPUs to force them to pick up the modified instruction.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
[heiko.carstens@de.ibm.com]: Change jump_label_make_nop() so we get
                             brcl 0,offset instead of brcl 0,0. This
                             makes sure that only the mask part of the
                             instruction gets changed when updated.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2019-05-17 12:50:43 +02:00 committed by Heiko Carstens
parent f2c7c76c5d
commit a646ef398e
2 changed files with 10 additions and 17 deletions
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18
arch/s390/kernel/jump_label.c
View File

@ -22,9 +22,9 @@ struct insn_args {
static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn) static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
{ {
/* brcl 0,0 */ /* brcl 0,offset */
insn->opcode = 0xc004; insn->opcode = 0xc004;
insn->offset = 0; insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
} }
static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn) static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
@ -77,23 +77,15 @@ static void __jump_label_transform(struct jump_entry *entry,
s390_kernel_write(code, &new, sizeof(new)); s390_kernel_write(code, &new, sizeof(new));
} }
static int __sm_arch_jump_label_transform(void *data) static void __jump_label_sync(void *dummy)
{ {
struct insn_args *args = data;
__jump_label_transform(args->entry, args->type, 0);
return 0;
} }
void arch_jump_label_transform(struct jump_entry *entry, void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type) enum jump_label_type type)
{ {
struct insn_args args; __jump_label_transform(entry, type, 0);
smp_call_function(__jump_label_sync, NULL, 1);
args.entry = entry;
args.type = type;
stop_machine_cpuslocked(__sm_arch_jump_label_transform, &args, NULL);
} }
void arch_jump_label_transform_static(struct jump_entry *entry, void arch_jump_label_transform_static(struct jump_entry *entry,

9
arch/s390/mm/maccess.c
View File

@ -52,21 +52,22 @@ static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t siz
* Therefore we have a read-modify-write sequence: the function reads eight * Therefore we have a read-modify-write sequence: the function reads eight
* bytes from destination at an eight byte boundary, modifies the bytes * bytes from destination at an eight byte boundary, modifies the bytes
* requested and writes the result back in a loop. * requested and writes the result back in a loop.
*
* Note: this means that this function may not be called concurrently on
* several cpus with overlapping words, since this may potentially
* cause data corruption.
*/ */
static DEFINE_SPINLOCK(s390_kernel_write_lock);
void notrace s390_kernel_write(void *dst, const void *src, size_t size) void notrace s390_kernel_write(void *dst, const void *src, size_t size)
{ {
unsigned long flags;
long copied; long copied;
spin_lock_irqsave(&s390_kernel_write_lock, flags);
while (size) { while (size) {
copied = s390_kernel_write_odd(dst, src, size); copied = s390_kernel_write_odd(dst, src, size);
dst += copied; dst += copied;
src += copied; src += copied;
size -= copied; size -= copied;
} }
spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
} }
static int __memcpy_real(void *dest, void *src, size_t count) static int __memcpy_real(void *dest, void *src, size_t count)