[PATCH 1/2] powerpc/8xx: Refactor calculation of number of entries per PTE in page tables

From: Christophe Leroy
Date: Mon Aug 31 2020 - 04:30:56 EST


On 8xx, the number of entries occupied by a PTE in the page tables
depends on the size of the page. At the time being, this calculation
is done in two places: in pte_update() and in set_huge_pte_at()

Refactor this calculation into a helper called
number_of_cells_per_pte(). For the time being, the val param is
unused. It will be used by following patch.

Instead of opencoding is_hugepd(), use hugepd_ok() with a forward
declaration.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
arch/powerpc/include/asm/nohash/32/pgtable.h | 18 ++++++++++++------
arch/powerpc/mm/pgtable.c | 6 ++++--
2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index b9e134d0f03a..80bbc21b87f0 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -227,6 +227,17 @@ static inline void pmd_clear(pmd_t *pmdp)
*/
#ifdef CONFIG_PPC_8xx
static pmd_t *pmd_off(struct mm_struct *mm, unsigned long addr);
+static int hugepd_ok(hugepd_t hpd);
+
+static int number_of_cells_per_pte(pmd_t *pmd, pte_basic_t val, int huge)
+{
+ if (!huge)
+ return PAGE_SIZE / SZ_4K;
+ else if (hugepd_ok(*((hugepd_t *)pmd)))
+ return 1;
+ else
+ return SZ_512K / SZ_4K;
+}

static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, pte_t *p,
unsigned long clr, unsigned long set, int huge)
@@ -237,12 +248,7 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, p
int num, i;
pmd_t *pmd = pmd_off(mm, addr);

- if (!huge)
- num = PAGE_SIZE / SZ_4K;
- else if ((pmd_val(*pmd) & _PMD_PAGE_MASK) != _PMD_PAGE_8M)
- num = SZ_512K / SZ_4K;
- else
- num = 1;
+ num = number_of_cells_per_pte(pmd, new, huge);

for (i = 0; i < num; i++, entry++, new += SZ_4K)
*entry = new;
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 9c0547d77af3..2dcad640b869 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -266,8 +266,7 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_
pmd_t *pmd = pmd_off(mm, addr);
pte_basic_t val;
pte_basic_t *entry = &ptep->pte;
- int num = is_hugepd(*((hugepd_t *)pmd)) ? 1 : SZ_512K / SZ_4K;
- int i;
+ int num, i;

/*
* Make sure hardware valid bit is not set. We don't do
@@ -280,6 +279,9 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_
pte = set_pte_filter(pte);

val = pte_val(pte);
+
+ num = number_of_cells_per_pte(pmd, val, 1);
+
for (i = 0; i < num; i++, entry++, val += SZ_4K)
*entry = val;
}
--
2.25.0