Messages in this thread Patch in this message | | | From | Christophe Leroy <> | Subject | How to handle PTE tables with non contiguous entries ? | Date | Mon, 10 Sep 2018 14:34:37 +0000 |
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Hi,
I'm having a hard time figuring out the best way to handle the following situation:
On the powerpc8xx, handling 16k size pages requires to have page tables with 4 identical entries.
Initially I was thinking about handling this by simply modifying pte_index() which changing pte_t type in order to have one entry every 16 bytes, then replicate the PTE value at *ptep, *ptep+1,*ptep+2 and *ptep+3 both in set_pte_at() and pte_update().
However, this doesn't work because many many places in the mm core part of the kernel use loops on ptep with single ptep++ increment.
Therefore did it with the following hack:
/* PTE level */ +#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PPC_16K_PAGES) +typedef struct { pte_basic_t pte, pte1, pte2, pte3; } pte_t; +#else typedef struct { pte_basic_t pte; } pte_t; +#endif
@@ -181,7 +192,13 @@ static inline unsigned long pte_update(pte_t *p, : "cc" ); #else /* PTE_ATOMIC_UPDATES */ unsigned long old = pte_val(*p); - *p = __pte((old & ~clr) | set); + unsigned long new = (old & ~clr) | set; + +#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PPC_16K_PAGES) + p->pte = p->pte1 = p->pte2 = p->pte3 = new; +#else + *p = __pte(new); +#endif #endif /* !PTE_ATOMIC_UPDATES */
#ifdef CONFIG_44x
@@ -161,7 +161,11 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr, /* Anything else just stores the PTE normally. That covers all 64-bit * 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); +#else *ptep = pte; +#endif
But I'm not too happy with it as it means pte_t is not a single type anymore so passing it from one function to the other is quite heavy.
Would someone have an idea of an elegent way to handle that ?
Thanks Christophe
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