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

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Message-ID: <20231205173252.62305-1-imbrenda@linux.ibm.com>
Date:   Tue,  5 Dec 2023 18:32:52 +0100
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-s390@...r.kernel.org,
        linux390-list@...maker.boeblingen.de.ibm.com,
        kvm390-list@...maker.boeblingen.de.ibm.com, hca@...ux.ibm.com,
        borntraeger@...ibm.com, frankja@...ux.ibm.com, nrb@...ux.ibm.com,
        nsg@...ux.ibm.com, svens@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com
Subject: [PATCH v1 1/1] s390: mm: convert pgste locking functions to C

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@...ux.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