[PATCH v1 1/1] s390: mm: convert pgste locking functions to C

Claudio Imbrenda
2023-12-05T17:33:01Z

Convert pgste_get_lock() and pgste_set_unlock() to C.

There is no real reasons to keep them in assembler. Having them in C
makes them more readable and maintainable, and better instructions are
used automatically when available.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
arch/s390/mm/pgtable.c | 29 ++++++++++-------------------
1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 3bd2ab2a9a34..6c4523aa4fdf 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -125,32 +125,23 @@ static inline pte_t ptep_flush_lazy(struct mm_struct *mm,

static inline pgste_t pgste_get_lock(pte_t *ptep)
{
- unsigned long new = 0;
+ unsigned long value = 0;
#ifdef CONFIG_PGSTE
- unsigned long old;
-
- asm(
- " lg %0,%2\n"
- "0: lgr %1,%0\n"
- " nihh %0,0xff7f\n" /* clear PCL bit in old */
- " oihh %1,0x0080\n" /* set PCL bit in new */
- " csg %0,%1,%2\n"
- " jl 0b\n"
- : "=&d" (old), "=&d" (new), "=Q" (ptep[PTRS_PER_PTE])
- : "Q" (ptep[PTRS_PER_PTE]) : "cc", "memory");
+ unsigned long *ptr = (unsigned long *)(ptep + PTRS_PER_PTE);
+
+ do {
+ value = __atomic64_or_barrier(PGSTE_PCL_BIT, ptr);
+ } while (value & PGSTE_PCL_BIT);
+ value |= PGSTE_PCL_BIT;
#endif
- return __pgste(new);
+ return __pgste(value);
}

static inline void pgste_set_unlock(pte_t *ptep, pgste_t pgste)
{
#ifdef CONFIG_PGSTE
- asm(
- " nihh %1,0xff7f\n" /* clear PCL bit */
- " stg %1,%0\n"
- : "=Q" (ptep[PTRS_PER_PTE])
- : "d" (pgste_val(pgste)), "Q" (ptep[PTRS_PER_PTE])
- : "cc", "memory");
+ barrier();
+ WRITE_ONCE(*(unsigned long *)(ptep + PTRS_PER_PTE), pgste_val(pgste) & ~PGSTE_PCL_BIT);
#endif
}

--
2.43.0