From 16f1c746755836aa823658000493cdab8ce7b098 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Tue, 8 May 2007 16:27:27 +1000 Subject: [PATCH] [POWERPC] Small fixes & cleanups in segment page size demotion The code for demoting segments to 4K had some issues, like for example, when using _PAGE_4K_PFN flag, the first CPU to hit it would do the demotion, but other CPUs hitting the same page wouldn't properly flush their SLBs if mmu_ci_restriction isn't set. There are also potential issues with hash_preload not handling _PAGE_4K_PFN. All of these are non issues on current hardware but might bite us in the future. This patch thus fixes it by: - Taking the test comparing the mm and current CPU context page sizes to decide to flush SLBs out of the mmu_ci_restrictions test since that can also be triggered by _PAGE_4K_PFN pages - Due to the above being done all the time, demote_segment_4k doesn't need update the context and flush the SLB - demote_segment_4k can be static and doesn't need an EXPORT_SYMBOL - Making hash_preload ignore anything that has either _PAGE_4K_PFN or _PAGE_NO_CACHE set, thus avoiding duplication of the complicated logic in hash_page() (and possibly making hash_preload a little bit faster for the normal case). Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras --- arch/powerpc/mm/hash_utils_64.c | 87 +++++++++++++++++---------------- 1 file changed, 46 insertions(+), 41 deletions(-) diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c index 9b226fa7006f..71092c2f65cd 100644 --- a/arch/powerpc/mm/hash_utils_64.c +++ b/arch/powerpc/mm/hash_utils_64.c @@ -596,22 +596,18 @@ unsigned int hash_page_do_lazy_icache(unsigned int pp, pte_t pte, int trap) * Demote a segment to using 4k pages. * For now this makes the whole process use 4k pages. */ -void demote_segment_4k(struct mm_struct *mm, unsigned long addr) -{ #ifdef CONFIG_PPC_64K_PAGES +static void demote_segment_4k(struct mm_struct *mm, unsigned long addr) +{ if (mm->context.user_psize == MMU_PAGE_4K) return; mm->context.user_psize = MMU_PAGE_4K; mm->context.sllp = SLB_VSID_USER | mmu_psize_defs[MMU_PAGE_4K].sllp; - get_paca()->context = mm->context; - slb_flush_and_rebolt(); #ifdef CONFIG_SPE_BASE spu_flush_all_slbs(mm); #endif -#endif } - -EXPORT_SYMBOL_GPL(demote_segment_4k); +#endif /* CONFIG_PPC_64K_PAGES */ /* Result code is: * 0 - handled @@ -711,40 +707,42 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap) psize = MMU_PAGE_4K; } - if (mmu_ci_restrictions) { - /* If this PTE is non-cacheable, switch to 4k */ - if (psize == MMU_PAGE_64K && - (pte_val(*ptep) & _PAGE_NO_CACHE)) { - if (user_region) { - demote_segment_4k(mm, ea); - psize = MMU_PAGE_4K; - } else if (ea < VMALLOC_END) { - /* - * some driver did a non-cacheable mapping - * in vmalloc space, so switch vmalloc - * to 4k pages - */ - printk(KERN_ALERT "Reducing vmalloc segment " - "to 4kB pages because of " - "non-cacheable mapping\n"); - psize = mmu_vmalloc_psize = MMU_PAGE_4K; - } + /* If this PTE is non-cacheable and we have restrictions on + * using non cacheable large pages, then we switch to 4k + */ + if (mmu_ci_restrictions && psize == MMU_PAGE_64K && + (pte_val(*ptep) & _PAGE_NO_CACHE)) { + if (user_region) { + demote_segment_4k(mm, ea); + psize = MMU_PAGE_4K; + } else if (ea < VMALLOC_END) { + /* + * some driver did a non-cacheable mapping + * in vmalloc space, so switch vmalloc + * to 4k pages + */ + printk(KERN_ALERT "Reducing vmalloc segment " + "to 4kB pages because of " + "non-cacheable mapping\n"); + psize = mmu_vmalloc_psize = MMU_PAGE_4K; #ifdef CONFIG_SPE_BASE spu_flush_all_slbs(mm); #endif } - if (user_region) { - if (psize != get_paca()->context.user_psize) { - get_paca()->context = mm->context; - slb_flush_and_rebolt(); - } - } else if (get_paca()->vmalloc_sllp != - mmu_psize_defs[mmu_vmalloc_psize].sllp) { - get_paca()->vmalloc_sllp = - mmu_psize_defs[mmu_vmalloc_psize].sllp; + } + if (user_region) { + if (psize != get_paca()->context.user_psize) { + get_paca()->context.user_psize = + mm->context.user_psize; slb_flush_and_rebolt(); } + } else if (get_paca()->vmalloc_sllp != + mmu_psize_defs[mmu_vmalloc_psize].sllp) { + get_paca()->vmalloc_sllp = + mmu_psize_defs[mmu_vmalloc_psize].sllp; + slb_flush_and_rebolt(); } + if (psize == MMU_PAGE_64K) rc = __hash_page_64K(ea, access, vsid, ptep, trap, local); else @@ -780,13 +778,26 @@ void hash_preload(struct mm_struct *mm, unsigned long ea, DBG_LOW("hash_preload(mm=%p, mm->pgdir=%p, ea=%016lx, access=%lx," " trap=%lx\n", mm, mm->pgd, ea, access, trap); - /* Get PTE, VSID, access mask */ + /* Get Linux PTE if available */ pgdir = mm->pgd; if (pgdir == NULL) return; ptep = find_linux_pte(pgdir, ea); if (!ptep) return; + +#ifdef CONFIG_PPC_64K_PAGES + /* If either _PAGE_4K_PFN or _PAGE_NO_CACHE is set (and we are on + * a 64K kernel), then we don't preload, hash_page() will take + * care of it once we actually try to access the page. + * That way we don't have to duplicate all of the logic for segment + * page size demotion here + */ + if (pte_val(*ptep) & (_PAGE_4K_PFN | _PAGE_NO_CACHE)) + return; +#endif /* CONFIG_PPC_64K_PAGES */ + + /* Get VSID */ vsid = get_vsid(mm->context.id, ea); /* Hash it in */ @@ -797,12 +808,6 @@ void hash_preload(struct mm_struct *mm, unsigned long ea, #ifndef CONFIG_PPC_64K_PAGES __hash_page_4K(ea, access, vsid, ptep, trap, local); #else - if (mmu_ci_restrictions) { - /* If this PTE is non-cacheable, switch to 4k */ - if (mm->context.user_psize == MMU_PAGE_64K && - (pte_val(*ptep) & _PAGE_NO_CACHE)) - demote_segment_4k(mm, ea); - } if (mm->context.user_psize == MMU_PAGE_64K) __hash_page_64K(ea, access, vsid, ptep, trap, local); else