Messages in this thread |  | | Subject | Re: [PATCH v2 1/5] powerpc/mm: Enhance 'slice' for supporting PPC32 | | From | "Aneesh Kumar K.V" <> | | Date | Fri, 19 Jan 2018 14:43:11 +0530 |
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On 01/19/2018 02:37 PM, Christophe LEROY wrote: > > > Le 19/01/2018 à 10:02, Aneesh Kumar K.V a écrit : >> >> >> On 01/19/2018 02:14 PM, Christophe LEROY wrote: >>> >>> >>> Le 19/01/2018 à 09:24, Aneesh Kumar K.V a écrit : >>>> Christophe Leroy <christophe.leroy@c-s.fr> writes: >>>> >>>>> In preparation for the following patch which will fix an issue on >>>>> the 8xx by re-using the 'slices', this patch enhances the >>>>> 'slices' implementation to support 32 bits CPUs. >>>>> >>>>> On PPC32, the address space is limited to 4Gbytes, hence only the low >>>>> slices will be used. As of today, the code uses >>>>> SLICE_LOW_TOP (0x100000000ul) and compares it with addr to determine >>>>> if addr refers to low or high space. >>>>> On PPC32, such a (addr < SLICE_LOW_TOP) test is always false because >>>>> 0x100000000ul degrades to 0. Therefore, the patch modifies >>>>> SLICE_LOW_TOP to (0xfffffffful) and modifies the tests to >>>>> (addr <= SLICE_LOW_TOP) which will then always be true on PPC32 >>>>> as addr has type 'unsigned long' while not modifying the PPC64 >>>>> behaviour. >>>>> >>>>> This patch moves "slices" functions prototypes from page64.h to page.h >>>>> >>>>> The high slices use bitmaps. As bitmap functions are not prepared to >>>>> handling bitmaps of size 0, the bitmap_xxx() calls are wrapped into >>>>> slice_bitmap_xxx() macros which will take care of the 0 nbits case. >>>>> >>>>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> >>>>> --- >>>>> v2: First patch of v1 serie split in two parts ; added >>>>> slice_bitmap_xxx() macros. >>>>> >>>>> arch/powerpc/include/asm/page.h | 14 +++++++++ >>>>> arch/powerpc/include/asm/page_32.h | 19 ++++++++++++ >>>>> arch/powerpc/include/asm/page_64.h | 21 ++----------- >>>>> arch/powerpc/mm/hash_utils_64.c | 2 +- >>>>> arch/powerpc/mm/mmu_context_nohash.c | 7 +++++ >>>>> arch/powerpc/mm/slice.c | 60 >>>>> ++++++++++++++++++++++++------------ >>>>> 6 files changed, 83 insertions(+), 40 deletions(-) >>>>> >>>>> diff --git a/arch/powerpc/include/asm/page.h >>>>> b/arch/powerpc/include/asm/page.h >>>>> index 8da5d4c1cab2..d0384f9db9eb 100644 >>>>> --- a/arch/powerpc/include/asm/page.h >>>>> +++ b/arch/powerpc/include/asm/page.h >>>>> @@ -342,6 +342,20 @@ typedef struct page *pgtable_t; >>>>> #endif >>>>> #endif >>>>> +#ifdef CONFIG_PPC_MM_SLICES >>>>> +struct mm_struct; >>>>> + >>>>> +unsigned long slice_get_unmapped_area(unsigned long addr, unsigned >>>>> long len, >>>>> + unsigned long flags, unsigned int psize, >>>>> + int topdown); >>>>> + >>>>> +unsigned int get_slice_psize(struct mm_struct *mm, unsigned long >>>>> addr); >>>>> + >>>>> +void slice_set_user_psize(struct mm_struct *mm, unsigned int psize); >>>>> +void slice_set_range_psize(struct mm_struct *mm, unsigned long start, >>>>> + unsigned long len, unsigned int psize); >>>>> +#endif >>>>> + >>>> >>>> Should we do a slice.h ? the way we have other files? and then do >>> >>> Yes we could add a slice.h instead of using page.h for that, good idea. >>> >>>> >>>> arch/powerpc/include/asm/book3s/64/slice.h that will carry >>>> #define slice_bitmap_zero(dst, nbits) \ >>>> do { if (nbits) bitmap_zero(dst, nbits); } while (0) >>>> #define slice_bitmap_set(dst, pos, nbits) \ >>>> do { if (nbits) bitmap_set(dst, pos, nbits); } while (0) >>>> #define slice_bitmap_copy(dst, src, nbits) \ >>>> do { if (nbits) bitmap_copy(dst, src, nbits); } while (0) >>>> #define slice_bitmap_and(dst, src1, src2, nbits) \ >>>> ({ (nbits) ? bitmap_and(dst, src1, src2, nbits) : 0; }) >>>> #define slice_bitmap_or(dst, src1, src2, nbits) \ >>>> do { if (nbits) bitmap_or(dst, src1, src2, nbits); } while (0) >>>> #define slice_bitmap_andnot(dst, src1, src2, nbits) \ >>>> ({ (nbits) ? bitmap_andnot(dst, src1, src2, nbits) : 0; }) >>>> #define slice_bitmap_equal(src1, src2, nbits) \ >>>> ({ (nbits) ? bitmap_equal(src1, src2, nbits) : 1; }) >>>> #define slice_bitmap_empty(src, nbits) \ >>>> ({ (nbits) ? bitmap_empty(src, nbits) : 1; }) >>>> >>>> This without that if(nbits) check and a proper static inline so that we >>>> can do type checking. >>> >>> Is it really worth duplicating that just for eliminating the 'if >>> (nbits)' in one case ? >>> >>> Only in book3s/64 we will be able to eliminate that, for nohash/32 we >>> need to keep the test due to the difference between low and high slices. >> >> the other advantage is we move the SLICE_LOW_SHIFT to the right >> location. IMHO mm subystem is really complex with these really >> overloaded headers. If we can keep it seperate we should with minimal >> code duplication? > > For the constants I fully agree with your proposal and I will do it. I > was only questionning the benefit of moving the slice_bitmap_xxxx() > stuff, taking into account that the 'if (nbits)' test is already > eliminated by the compiler. >
That is compiler dependent as you are finding with the other patch where if (0) didn't get compiled out
-aneesh
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