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Violators will be prosecuted for from ; Fri, 19 Jan 2018 02:13:20 -0700 Subject: Re: [PATCH v2 1/5] powerpc/mm: Enhance 'slice' for supporting PPC32 To: Christophe LEROY , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Scott Wood Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <49148d07955d3e5f963cedf9adcfcc37c3e03ef4.1516179904.git.christophe.leroy@c-s.fr> <87vafyz265.fsf@linux.vnet.ibm.com> <84dc1df4-db2f-be11-c1f3-5dddd1e44983@c-s.fr> <28c3ba39-ef31-5ff3-7672-3e9d1942be94@c-s.fr> From: "Aneesh Kumar K.V" Date: Fri, 19 Jan 2018 14:43:11 +0530 MIME-Version: 1.0 In-Reply-To: <28c3ba39-ef31-5ff3-7672-3e9d1942be94@c-s.fr> Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 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 >>>>> --- >>>>>   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