2022-09-28 06:42:13

by Christophe Leroy

Subject: [PATCH] powerpc/8xx: Reverse order entries are written by __set_pte_at()

At the time being, with 16k pages __set_pte_at() writes table entries
in reverse order:

294: 91 49 00 0c stw r10,12(r9)
298: 91 49 00 08 stw r10,8(r9)
29c: 91 49 00 04 stw r10,4(r9)
2a0: 91 49 00 00 stw r10,0(r9)

Allthough there should be no impact at all as it stays in a single
cacheline, reverse the writing in a more natural order.

288: 91 49 00 0c stw r10,0(r9)
28c: 91 49 00 08 stw r10,4(r9)
290: 91 49 00 04 stw r10,8(r9)
294: 91 49 00 00 stw r10,12(r9)

Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/include/asm/nohash/pgtable.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 4fd73c7412d0..d2e39823af09 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -183,7 +183,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
* cases, and 32-bit non-hash with 32-bit PTEs.
*/
#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PPC_16K_PAGES)
- ptep->pte = ptep->pte1 = ptep->pte2 = ptep->pte3 = pte_val(pte);
+ ptep->pte3 = ptep->pte2 = ptep->pte1 = ptep->pte = pte_val(pte);
#else
*ptep = pte;
#endif
--
2.37.1

2022-11-30 09:41:06

by Michael Ellerman

Subject: Re: [PATCH] powerpc/8xx: Reverse order entries are written by __set_pte_at()

On Wed, 28 Sep 2022 08:29:22 +0200, Christophe Leroy wrote:
> At the time being, with 16k pages __set_pte_at() writes table entries
> in reverse order:
>
> 294: 91 49 00 0c stw r10,12(r9)
> 298: 91 49 00 08 stw r10,8(r9)
> 29c: 91 49 00 04 stw r10,4(r9)
> 2a0: 91 49 00 00 stw r10,0(r9)
>
> [...]

Applied to powerpc/next.

[1/1] powerpc/8xx: Reverse order entries are written by __set_pte_at()
https://git.kernel.org/powerpc/c/0b4721815c5328e08c3acdee4a53890e012d830b

cheers