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Date: Fri, 31 Jan 2020 09:38:13 +0000 From: Will Deacon <will@...nel.org> To: Greg Ungerer <gerg@...ux-m68k.org> Cc: Peter Zijlstra <peterz@...radead.org>, Geert Uytterhoeven <geert@...ux-m68k.org>, linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 0/5] Rewrite Motorola MMU page-table layout Hi Greg, On Fri, Jan 31, 2020 at 04:31:48PM +1000, Greg Ungerer wrote: > On 29/1/20 8:39 pm, Peter Zijlstra wrote: > > In order to faciliate Will's READ_ONCE() patches: > > > > https://lkml.kernel.org/r/20200123153341.19947-1-will@kernel.org > > > > we need to fix m68k/motorola to not have a giant pmd_t. These patches do so and > > are tested using ARAnyM/68040. > > > > It would be very good if someone can either test or tell us what emulator to > > use for 020/030. > > This series breaks compilation for the ColdFire (with MMU) variant of > the m68k family: [...] > Easy to reproduce. Build for the m5475evb_defconfig. I've hacked up a fix below, but I don't know how to test whether it actually works (it does fix the build). However, I also notice that building for m5475evb_defconfig with vanilla v5.5 triggers this scary looking warning due to a mismatch between the pgd size and the (8k!) page size: | In function 'pgd_alloc.isra.111', | inlined from 'mm_alloc_pgd' at kernel/fork.c:634:12, | inlined from 'mm_init.isra.112' at kernel/fork.c:1043:6: | ./arch/m68k/include/asm/string.h:72:25: warning: '__builtin_memcpy' forming offset [4097, 8192] is out of the bounds [0, 4096] of object 'kernel_pg_dir' with type 'pgd_t[1024]' {aka 'struct <anonymous>[1024]'} [-Warray-bounds] | #define memcpy(d, s, n) __builtin_memcpy(d, s, n) | ^~~~~~~~~~~~~~~~~~~~~~~~~ | ./arch/m68k/include/asm/mcf_pgalloc.h:93:2: note: in expansion of macro 'memcpy' | memcpy(new_pgd, swapper_pg_dir, PAGE_SIZE); | ^~~~~~ I think the correct fix is to add this: diff --git a/arch/m68k/include/asm/mcf_pgalloc.h b/arch/m68k/include/asm/mcf_pgalloc.h index 82ec54c2eaa4..c335e6a381a1 100644 --- a/arch/m68k/include/asm/mcf_pgalloc.h +++ b/arch/m68k/include/asm/mcf_pgalloc.h @@ -90,7 +90,7 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm) new_pgd = (pgd_t *)__get_free_page(GFP_DMA | __GFP_NOWARN); if (!new_pgd) return NULL; - memcpy(new_pgd, swapper_pg_dir, PAGE_SIZE); + memcpy(new_pgd, swapper_pg_dir, PTRS_PER_PGD * sizeof(pgd_t)); memset(new_pgd, 0, PAGE_OFFSET >> PGDIR_SHIFT); return new_pgd; } but maybe it should be done as a separate patch give that it's not caused by the rework we've been doing. Will --->8 diff --git a/arch/m68k/include/asm/mcf_pgalloc.h b/arch/m68k/include/asm/mcf_pgalloc.h index 82ec54c2eaa4..955d54a6e973 100644 --- a/arch/m68k/include/asm/mcf_pgalloc.h +++ b/arch/m68k/include/asm/mcf_pgalloc.h @@ -28,21 +28,22 @@ extern inline pmd_t *pmd_alloc_kernel(pgd_t *pgd, unsigned long address) return (pmd_t *) pgd; } -#define pmd_populate(mm, pmd, page) (pmd_val(*pmd) = \ - (unsigned long)(page_address(page))) +#define pmd_populate(mm, pmd, pte) (pmd_val(*pmd) = (unsigned long)(pte)) -#define pmd_populate_kernel(mm, pmd, pte) (pmd_val(*pmd) = (unsigned long)(pte)) +#define pmd_populate_kernel pmd_populate -#define pmd_pgtable(pmd) pmd_page(pmd) +#define pmd_pgtable(pmd) pfn_to_virt(pmd_val(pmd) >> PAGE_SHIFT) -static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t page, +static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pgtable, unsigned long address) { + struct page *page = virt_to_page(pgtable); + pgtable_pte_page_dtor(page); __free_page(page); } -static inline struct page *pte_alloc_one(struct mm_struct *mm) +static inline pgtable_t pte_alloc_one(struct mm_struct *mm) { struct page *page = alloc_pages(GFP_DMA, 0); pte_t *pte; @@ -54,20 +55,19 @@ static inline struct page *pte_alloc_one(struct mm_struct *mm) return NULL; } - pte = kmap(page); - if (pte) { - clear_page(pte); - __flush_page_to_ram(pte); - flush_tlb_kernel_page(pte); - nocache_page(pte); - } - kunmap(page); + pte = page_address(page); + clear_page(pte); + __flush_page_to_ram(pte); + flush_tlb_kernel_page(pte); + nocache_page(pte); - return page; + return pte; } -static inline void pte_free(struct mm_struct *mm, struct page *page) +static inline void pte_free(struct mm_struct *mm, pgtable_t pgtable) { + struct page *page = virt_to_page(pgtable); + pgtable_pte_page_dtor(page); __free_page(page); }
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