[v4,2/5] powerpc/mm/slice: Enhance for supporting PPC32

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.

This patch moves "slices" functions prototypes from page64.h to slice.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() functions which will void on PPC32

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.
 v3: Moving slice related stuff in slice.h and slice_32/64.h
     slice_bitmap_xxx() are now static inline functions and platform dependent
     SLICE_LOW_TOP declared ull on PPC32 with correct casts allows to keep it 0x100000000
 v4: Moved slice_32.h and slice_64.h to respective subarch dirs
     Moved somes #ifdefs from asm/slice.h to respective subarch slice.h
     SLICE_LOW_ details distributed in repective subarch slices allthough they are identical for the moment

 arch/powerpc/include/asm/book3s/64/slice.h | 79 ++++++++++++++++++++++++++++++
 arch/powerpc/include/asm/nohash/32/slice.h | 65 ++++++++++++++++++++++++
 arch/powerpc/include/asm/nohash/64/slice.h | 12 +++++
 arch/powerpc/include/asm/page.h            |  1 +
 arch/powerpc/include/asm/page_64.h         | 59 ----------------------
 arch/powerpc/include/asm/slice.h           | 42 ++++++++++++++++
 arch/powerpc/mm/slice.c                    | 38 ++++++++------
 7 files changed, 221 insertions(+), 75 deletions(-)
 create mode 100644 arch/powerpc/include/asm/book3s/64/slice.h
 create mode 100644 arch/powerpc/include/asm/nohash/32/slice.h
 create mode 100644 arch/powerpc/include/asm/nohash/64/slice.h
 create mode 100644 arch/powerpc/include/asm/slice.h

On Sat, 10 Feb 2018 13:54:27 +0100 (CET)
Christophe Leroy <christophe.leroy@c-s.fr> wrote:

> 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.
> 
> This patch moves "slices" functions prototypes from page64.h to slice.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() functions which will void on PPC32

On this last point, I think it would be better to put these with the
existing slice bitmap functions in slice.c and just have a few #ifdefs
for SLICE_NUM_HIGH == 0.

Thanks,
Nick

On 02/11/2018 07:29 PM, Nicholas Piggin wrote:
> On Sat, 10 Feb 2018 13:54:27 +0100 (CET)
> Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> 
>> 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.
>>
>> This patch moves "slices" functions prototypes from page64.h to slice.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() functions which will void on PPC32
> 
> On this last point, I think it would be better to put these with the
> existing slice bitmap functions in slice.c and just have a few #ifdefs
> for SLICE_NUM_HIGH == 0.
> 

We went back and forth with that. IMHO, we should avoid as much #ifdef 
as possible across platforms. It helps to understand the platform 
restrictions better as we have less and less access to these platforms. 
The above change indicates that nohash 32 wants to use the slice code 
and they have different restrictions. With that we now know that 
book3s64 and nohash 32 are the two different configs using slice code.

-aneesh

On Sun, 11 Feb 2018 21:04:42 +0530
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:

> On 02/11/2018 07:29 PM, Nicholas Piggin wrote:
> > On Sat, 10 Feb 2018 13:54:27 +0100 (CET)
> > Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> >   
> >> 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.
> >>
> >> This patch moves "slices" functions prototypes from page64.h to slice.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() functions which will void on PPC32  
> > 
> > On this last point, I think it would be better to put these with the
> > existing slice bitmap functions in slice.c and just have a few #ifdefs
> > for SLICE_NUM_HIGH == 0.
> >   
> 
> We went back and forth with that. IMHO, we should avoid as much #ifdef 
> as possible across platforms. It helps to understand the platform 
> restrictions better as we have less and less access to these platforms. 
> The above change indicates that nohash 32 wants to use the slice code 
> and they have different restrictions. With that we now know that 
> book3s64 and nohash 32 are the two different configs using slice code.

I don't think it's the right place to put it. It's not platform dependent
so much as it just depends on whether or not you have 0 high slices as
a workaround for bitmap API not accepting 0 length.

Another platform that uses the slice code would just have to copy and
paste either the nop or the bitmap implementation depending if it has
high slices. So I don't think it's the right abstraction. And it
implies a bitmap operation but it very specifically only works for
struct slice_mask.high_slices bitmap, which is not clear. Better to
just work with struct slice_mask.

Some ifdefs inside .c code for small helper functions like this IMO isn't
really a big deal -- it's not worse than having it in headers. You just
want to avoid ifdef mess when looking at non-trivial logic.

static inline void slice_or_mask(struct slice_mask *dst, struct slice_mask *src)
{
    dst->low_slices |= src->low_slices;
#if SLICE_NUM_HIGH > 0
    bitmap_or(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
#endif
}

I think that's pretty fine. If you have a singular hatred for ifdef in .c,
then if() works just as well.

Thanks,
Nick

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.
>
> This patch moves "slices" functions prototypes from page64.h to slice.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() functions which will void on PPC32
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

> 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.
>  v3: Moving slice related stuff in slice.h and slice_32/64.h
>      slice_bitmap_xxx() are now static inline functions and platform dependent
>      SLICE_LOW_TOP declared ull on PPC32 with correct casts allows to keep it 0x100000000
>  v4: Moved slice_32.h and slice_64.h to respective subarch dirs
>      Moved somes #ifdefs from asm/slice.h to respective subarch slice.h
>      SLICE_LOW_ details distributed in repective subarch slices allthough they are identical for the moment
>
>  arch/powerpc/include/asm/book3s/64/slice.h | 79 ++++++++++++++++++++++++++++++
>  arch/powerpc/include/asm/nohash/32/slice.h | 65 ++++++++++++++++++++++++
>  arch/powerpc/include/asm/nohash/64/slice.h | 12 +++++
>  arch/powerpc/include/asm/page.h            |  1 +
>  arch/powerpc/include/asm/page_64.h         | 59 ----------------------
>  arch/powerpc/include/asm/slice.h           | 42 ++++++++++++++++
>  arch/powerpc/mm/slice.c                    | 38 ++++++++------
>  7 files changed, 221 insertions(+), 75 deletions(-)
>  create mode 100644 arch/powerpc/include/asm/book3s/64/slice.h
>  create mode 100644 arch/powerpc/include/asm/nohash/32/slice.h
>  create mode 100644 arch/powerpc/include/asm/nohash/64/slice.h
>  create mode 100644 arch/powerpc/include/asm/slice.h
>
> diff --git a/arch/powerpc/include/asm/book3s/64/slice.h b/arch/powerpc/include/asm/book3s/64/slice.h
> new file mode 100644
> index 000000000000..f9a2c8bd7a77
> --- /dev/null
> +++ b/arch/powerpc/include/asm/book3s/64/slice.h
> @@ -0,0 +1,79 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_BOOK3S_64_SLICE_H
> +#define _ASM_POWERPC_BOOK3S_64_SLICE_H
> +
> +#ifdef CONFIG_PPC_MM_SLICES
> +
> +#define SLICE_LOW_SHIFT		28
> +#define SLICE_LOW_TOP		(0x100000000ul)
> +#define SLICE_NUM_LOW		(SLICE_LOW_TOP >> SLICE_LOW_SHIFT)
> +#define GET_LOW_SLICE_INDEX(addr)	((addr) >> SLICE_LOW_SHIFT)
> +
> +#define SLICE_HIGH_SHIFT	40
> +#define SLICE_NUM_HIGH		(H_PGTABLE_RANGE >> SLICE_HIGH_SHIFT)
> +#define GET_HIGH_SLICE_INDEX(addr)	((addr) >> SLICE_HIGH_SHIFT)
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <linux/bitmap.h>
> +
> +static inline void slice_bitmap_zero(unsigned long *dst, unsigned int nbits)
> +{
> +	bitmap_zero(dst, nbits);
> +}
> +
> +static inline int slice_bitmap_and(unsigned long *dst,
> +				   const unsigned long *src1,
> +				   const unsigned long *src2,
> +				   unsigned int nbits)
> +{
> +	return bitmap_and(dst, src1, src2, nbits);
> +}
> +
> +static inline void slice_bitmap_or(unsigned long *dst,
> +				   const unsigned long *src1,
> +				   const unsigned long *src2,
> +				   unsigned int nbits)
> +{
> +	bitmap_or(dst, src1, src2, nbits);
> +}
> +
> +static inline int slice_bitmap_andnot(unsigned long *dst,
> +				      const unsigned long *src1,
> +				      const unsigned long *src2,
> +				      unsigned int nbits)
> +{
> +	return bitmap_andnot(dst, src1, src2, nbits);
> +}
> +
> +static inline int slice_bitmap_equal(const unsigned long *src1,
> +				     const unsigned long *src2,
> +				     unsigned int nbits)
> +{
> +	return bitmap_equal(src1, src2, nbits);
> +}
> +
> +static inline int slice_bitmap_empty(const unsigned long *src, unsigned nbits)
> +{
> +	return bitmap_empty(src, nbits);
> +}
> +
> +static inline void slice_bitmap_set(unsigned long *map, unsigned int start,
> +				    unsigned int nbits)
> +{
> +	bitmap_set(map, start, nbits);
> +}
> +#endif /* __ASSEMBLY__ */
> +
> +#else /* CONFIG_PPC_MM_SLICES */
> +
> +#define get_slice_psize(mm, addr)	((mm)->context.user_psize)
> +#define slice_set_user_psize(mm, psize)		\
> +do {						\
> +	(mm)->context.user_psize = (psize);	\
> +	(mm)->context.sllp = SLB_VSID_USER | mmu_psize_defs[(psize)].sllp; \
> +} while (0)
> +
> +#endif /* CONFIG_PPC_MM_SLICES */
> +
> +#endif /* _ASM_POWERPC_BOOK3S_64_SLICE_H */
> diff --git a/arch/powerpc/include/asm/nohash/32/slice.h b/arch/powerpc/include/asm/nohash/32/slice.h
> new file mode 100644
> index 000000000000..bcb4924f7d22
> --- /dev/null
> +++ b/arch/powerpc/include/asm/nohash/32/slice.h
> @@ -0,0 +1,65 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_NOHASH_32_SLICE_H
> +#define _ASM_POWERPC_NOHASH_32_SLICE_H
> +
> +#ifdef CONFIG_PPC_MM_SLICES
> +
> +#define SLICE_LOW_SHIFT		28
> +#define SLICE_LOW_TOP		(0x100000000ull)
> +#define SLICE_NUM_LOW		(SLICE_LOW_TOP >> SLICE_LOW_SHIFT)
> +#define GET_LOW_SLICE_INDEX(addr)	((addr) >> SLICE_LOW_SHIFT)
> +
> +#define SLICE_HIGH_SHIFT	0
> +#define SLICE_NUM_HIGH		0ul
> +#define GET_HIGH_SLICE_INDEX(addr)	(addr & 0)
> +
> +#ifndef __ASSEMBLY__
> +
> +static inline void slice_bitmap_zero(unsigned long *dst, unsigned int nbits)
> +{
> +}
> +
> +static inline int slice_bitmap_and(unsigned long *dst,
> +				   const unsigned long *src1,
> +				   const unsigned long *src2,
> +				   unsigned int nbits)
> +{
> +	return 0;
> +}
> +
> +static inline void slice_bitmap_or(unsigned long *dst,
> +				   const unsigned long *src1,
> +				   const unsigned long *src2,
> +				   unsigned int nbits)
> +{
> +}
> +
> +static inline int slice_bitmap_andnot(unsigned long *dst,
> +				      const unsigned long *src1,
> +				      const unsigned long *src2,
> +				      unsigned int nbits)
> +{
> +	return 0;
> +}
> +
> +static inline int slice_bitmap_equal(const unsigned long *src1,
> +				     const unsigned long *src2,
> +				     unsigned int nbits)
> +{
> +	return 1;
> +}
> +
> +static inline int slice_bitmap_empty(const unsigned long *src, unsigned nbits)
> +{
> +	return 1;
> +}
> +
> +static inline void slice_bitmap_set(unsigned long *map, unsigned int start,
> +				    unsigned int nbits)
> +{
> +}
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* CONFIG_PPC_MM_SLICES */
> +
> +#endif /* _ASM_POWERPC_NOHASH_32_SLICE_H */
> diff --git a/arch/powerpc/include/asm/nohash/64/slice.h b/arch/powerpc/include/asm/nohash/64/slice.h
> new file mode 100644
> index 000000000000..ad0d6e3cc1c5
> --- /dev/null
> +++ b/arch/powerpc/include/asm/nohash/64/slice.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_NOHASH_64_SLICE_H
> +#define _ASM_POWERPC_NOHASH_64_SLICE_H
> +
> +#ifdef CONFIG_PPC_64K_PAGES
> +#define get_slice_psize(mm, addr)	MMU_PAGE_64K
> +#else /* CONFIG_PPC_64K_PAGES */
> +#define get_slice_psize(mm, addr)	MMU_PAGE_4K
> +#endif /* !CONFIG_PPC_64K_PAGES */
> +#define slice_set_user_psize(mm, psize)	do { BUG(); } while (0)
> +
> +#endif /* _ASM_POWERPC_NOHASH_64_SLICE_H */
> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index 8da5d4c1cab2..d5f1c41b7dba 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -344,5 +344,6 @@ typedef struct page *pgtable_t;
>  
>  #include <asm-generic/memory_model.h>
>  #endif /* __ASSEMBLY__ */
> +#include <asm/slice.h>
>  
>  #endif /* _ASM_POWERPC_PAGE_H */
> diff --git a/arch/powerpc/include/asm/page_64.h b/arch/powerpc/include/asm/page_64.h
> index 56234c6fcd61..af04acdb873f 100644
> --- a/arch/powerpc/include/asm/page_64.h
> +++ b/arch/powerpc/include/asm/page_64.h
> @@ -86,65 +86,6 @@ extern u64 ppc64_pft_size;
>  
>  #endif /* __ASSEMBLY__ */
>  
> -#ifdef CONFIG_PPC_MM_SLICES
> -
> -#define SLICE_LOW_SHIFT		28
> -#define SLICE_HIGH_SHIFT	40
> -
> -#define SLICE_LOW_TOP		(0x100000000ul)
> -#define SLICE_NUM_LOW		(SLICE_LOW_TOP >> SLICE_LOW_SHIFT)
> -#define SLICE_NUM_HIGH		(H_PGTABLE_RANGE >> SLICE_HIGH_SHIFT)
> -
> -#define GET_LOW_SLICE_INDEX(addr)	((addr) >> SLICE_LOW_SHIFT)
> -#define GET_HIGH_SLICE_INDEX(addr)	((addr) >> SLICE_HIGH_SHIFT)
> -
> -#ifndef __ASSEMBLY__
> -struct mm_struct;
> -
> -extern unsigned long slice_get_unmapped_area(unsigned long addr,
> -					     unsigned long len,
> -					     unsigned long flags,
> -					     unsigned int psize,
> -					     int topdown);
> -
> -extern unsigned int get_slice_psize(struct mm_struct *mm,
> -				    unsigned long addr);
> -
> -extern void slice_set_user_psize(struct mm_struct *mm, unsigned int psize);
> -extern void slice_set_range_psize(struct mm_struct *mm, unsigned long start,
> -				  unsigned long len, unsigned int psize);
> -
> -#endif /* __ASSEMBLY__ */
> -#else
> -#define slice_init()
> -#ifdef CONFIG_PPC_BOOK3S_64
> -#define get_slice_psize(mm, addr)	((mm)->context.user_psize)
> -#define slice_set_user_psize(mm, psize)		\
> -do {						\
> -	(mm)->context.user_psize = (psize);	\
> -	(mm)->context.sllp = SLB_VSID_USER | mmu_psize_defs[(psize)].sllp; \
> -} while (0)
> -#else /* !CONFIG_PPC_BOOK3S_64 */
> -#ifdef CONFIG_PPC_64K_PAGES
> -#define get_slice_psize(mm, addr)	MMU_PAGE_64K
> -#else /* CONFIG_PPC_64K_PAGES */
> -#define get_slice_psize(mm, addr)	MMU_PAGE_4K
> -#endif /* !CONFIG_PPC_64K_PAGES */
> -#define slice_set_user_psize(mm, psize)	do { BUG(); } while(0)
> -#endif /* CONFIG_PPC_BOOK3S_64 */
> -
> -#define slice_set_range_psize(mm, start, len, psize)	\
> -	slice_set_user_psize((mm), (psize))
> -#endif /* CONFIG_PPC_MM_SLICES */
> -
> -#ifdef CONFIG_HUGETLB_PAGE
> -
> -#ifdef CONFIG_PPC_MM_SLICES
> -#define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
> -#endif
> -
> -#endif /* !CONFIG_HUGETLB_PAGE */
> -
>  #define VM_DATA_DEFAULT_FLAGS \
>  	(is_32bit_task() ? \
>  	 VM_DATA_DEFAULT_FLAGS32 : VM_DATA_DEFAULT_FLAGS64)
> diff --git a/arch/powerpc/include/asm/slice.h b/arch/powerpc/include/asm/slice.h
> new file mode 100644
> index 000000000000..172711fadb1c
> --- /dev/null
> +++ b/arch/powerpc/include/asm/slice.h
> @@ -0,0 +1,42 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_SLICE_H
> +#define _ASM_POWERPC_SLICE_H
> +
> +#ifdef CONFIG_PPC_BOOK3S_64
> +#include <asm/book3s/64/slice.h>
> +#elif defined(CONFIG_PPC64)
> +#include <asm/nohash/64/slice.h>
> +#elif defined(CONFIG_PPC_MMU_NOHASH)
> +#include <asm/nohash/32/slice.h>
> +#endif
> +
> +#ifdef CONFIG_PPC_MM_SLICES
> +
> +#ifdef CONFIG_HUGETLB_PAGE
> +#define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
> +#endif
> +#define HAVE_ARCH_UNMAPPED_AREA
> +#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
> +
> +#ifndef __ASSEMBLY__
> +
> +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 /* __ASSEMBLY__ */
> +
> +#else /* CONFIG_PPC_MM_SLICES */
> +
> +#define slice_set_range_psize(mm, start, len, psize)	\
> +	slice_set_user_psize((mm), (psize))
> +#endif /* CONFIG_PPC_MM_SLICES */
> +
> +#endif /* _ASM_POWERPC_SLICE_H */
> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> index 98b53d48968f..549704dfa777 100644
> --- a/arch/powerpc/mm/slice.c
> +++ b/arch/powerpc/mm/slice.c
> @@ -73,10 +73,11 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
>  	unsigned long end = start + len - 1;
>  
>  	ret->low_slices = 0;
> -	bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
> +	slice_bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
>  
>  	if (start < SLICE_LOW_TOP) {
> -		unsigned long mend = min(end, (SLICE_LOW_TOP - 1));
> +		unsigned long mend = min(end,
> +					 (unsigned long)(SLICE_LOW_TOP - 1));
>  
>  		ret->low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
>  			- (1u << GET_LOW_SLICE_INDEX(start));
> @@ -87,7 +88,7 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
>  		unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));
>  		unsigned long count = GET_HIGH_SLICE_INDEX(align_end) - start_index;
>  
> -		bitmap_set(ret->high_slices, start_index, count);
> +		slice_bitmap_set(ret->high_slices, start_index, count);
>  	}
>  }
>  
> @@ -113,11 +114,13 @@ static int slice_high_has_vma(struct mm_struct *mm, unsigned long slice)
>  	unsigned long start = slice << SLICE_HIGH_SHIFT;
>  	unsigned long end = start + (1ul << SLICE_HIGH_SHIFT);
>  
> +#ifdef CONFIG_PPC64
>  	/* Hack, so that each addresses is controlled by exactly one
>  	 * of the high or low area bitmaps, the first high area starts
>  	 * at 4GB, not 0 */
>  	if (start == 0)
>  		start = SLICE_LOW_TOP;
> +#endif
>  
>  	return !slice_area_is_free(mm, start, end - start);
>  }
> @@ -128,7 +131,7 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
>  	unsigned long i;
>  
>  	ret->low_slices = 0;
> -	bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
> +	slice_bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
>  
>  	for (i = 0; i < SLICE_NUM_LOW; i++)
>  		if (!slice_low_has_vma(mm, i))
> @@ -151,7 +154,7 @@ static void slice_mask_for_size(struct mm_struct *mm, int psize, struct slice_ma
>  	u64 lpsizes;
>  
>  	ret->low_slices = 0;
> -	bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
> +	slice_bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
>  
>  	lpsizes = mm->context.low_slices_psize;
>  	for (i = 0; i < SLICE_NUM_LOW; i++)
> @@ -180,15 +183,16 @@ static int slice_check_fit(struct mm_struct *mm,
>  	 */
>  	unsigned long slice_count = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
>  
> -	bitmap_and(result, mask.high_slices,
> -		   available.high_slices, slice_count);
> +	slice_bitmap_and(result, mask.high_slices, available.high_slices,
> +			 slice_count);
>  
>  	return (mask.low_slices & available.low_slices) == mask.low_slices &&
> -		bitmap_equal(result, mask.high_slices, slice_count);
> +		slice_bitmap_equal(result, mask.high_slices, slice_count);
>  }
>  
>  static void slice_flush_segments(void *parm)
>  {
> +#ifdef CONFIG_PPC64
>  	struct mm_struct *mm = parm;
>  	unsigned long flags;
>  
> @@ -200,6 +204,7 @@ static void slice_flush_segments(void *parm)
>  	local_irq_save(flags);
>  	slb_flush_and_rebolt();
>  	local_irq_restore(flags);
> +#endif
>  }
>  
>  static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psize)
> @@ -389,16 +394,16 @@ static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
>  static inline void slice_or_mask(struct slice_mask *dst, struct slice_mask *src)
>  {
>  	dst->low_slices |= src->low_slices;
> -	bitmap_or(dst->high_slices, dst->high_slices, src->high_slices,
> -		  SLICE_NUM_HIGH);
> +	slice_bitmap_or(dst->high_slices, dst->high_slices, src->high_slices,
> +			SLICE_NUM_HIGH);
>  }
>  
>  static inline void slice_andnot_mask(struct slice_mask *dst, struct slice_mask *src)
>  {
>  	dst->low_slices &= ~src->low_slices;
>  
> -	bitmap_andnot(dst->high_slices, dst->high_slices, src->high_slices,
> -		      SLICE_NUM_HIGH);
> +	slice_bitmap_andnot(dst->high_slices, dst->high_slices,
> +			    src->high_slices, SLICE_NUM_HIGH);
>  }
>  
>  #ifdef CONFIG_PPC_64K_PAGES
> @@ -446,14 +451,14 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
>  	 * init different masks
>  	 */
>  	mask.low_slices = 0;
> -	bitmap_zero(mask.high_slices, SLICE_NUM_HIGH);
> +	slice_bitmap_zero(mask.high_slices, SLICE_NUM_HIGH);
>  
>  	/* silence stupid warning */;
>  	potential_mask.low_slices = 0;
> -	bitmap_zero(potential_mask.high_slices, SLICE_NUM_HIGH);
> +	slice_bitmap_zero(potential_mask.high_slices, SLICE_NUM_HIGH);
>  
>  	compat_mask.low_slices = 0;
> -	bitmap_zero(compat_mask.high_slices, SLICE_NUM_HIGH);
> +	slice_bitmap_zero(compat_mask.high_slices, SLICE_NUM_HIGH);
>  
>  	/* Sanity checks */
>  	BUG_ON(mm->task_size == 0);
> @@ -591,7 +596,8 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
>   convert:
>  	slice_andnot_mask(&mask, &good_mask);
>  	slice_andnot_mask(&mask, &compat_mask);
> -	if (mask.low_slices || !bitmap_empty(mask.high_slices, SLICE_NUM_HIGH)) {
> +	if (mask.low_slices ||
> +	    !slice_bitmap_empty(mask.high_slices, SLICE_NUM_HIGH)) {
>  		slice_convert(mm, mask, psize);
>  		if (psize > MMU_PAGE_BASE)
>  			on_each_cpu(slice_flush_segments, mm, 1);
> -- 
> 2.13.3

Le 12/02/2018 à 00:34, Nicholas Piggin a écrit :
> On Sun, 11 Feb 2018 21:04:42 +0530
> "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
> 
>> On 02/11/2018 07:29 PM, Nicholas Piggin wrote:
>>> On Sat, 10 Feb 2018 13:54:27 +0100 (CET)
>>> Christophe Leroy <christophe.leroy@c-s.fr> wrote:
>>>    
>>>> 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.
>>>>
>>>> This patch moves "slices" functions prototypes from page64.h to slice.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() functions which will void on PPC32
>>>
>>> On this last point, I think it would be better to put these with the
>>> existing slice bitmap functions in slice.c and just have a few #ifdefs
>>> for SLICE_NUM_HIGH == 0.
>>>    
>>
>> We went back and forth with that. IMHO, we should avoid as much #ifdef
>> as possible across platforms. It helps to understand the platform
>> restrictions better as we have less and less access to these platforms.
>> The above change indicates that nohash 32 wants to use the slice code
>> and they have different restrictions. With that we now know that
>> book3s64 and nohash 32 are the two different configs using slice code.
> 
> I don't think it's the right place to put it. It's not platform dependent
> so much as it just depends on whether or not you have 0 high slices as
> a workaround for bitmap API not accepting 0 length.
> 
> Another platform that uses the slice code would just have to copy and
> paste either the nop or the bitmap implementation depending if it has
> high slices. So I don't think it's the right abstraction. And it
> implies a bitmap operation but it very specifically only works for
> struct slice_mask.high_slices bitmap, which is not clear. Better to
> just work with struct slice_mask.
> 
> Some ifdefs inside .c code for small helper functions like this IMO isn't
> really a big deal -- it's not worse than having it in headers. You just
> want to avoid ifdef mess when looking at non-trivial logic.
> 
> static inline void slice_or_mask(struct slice_mask *dst, struct slice_mask *src)
> {
>      dst->low_slices |= src->low_slices;
> #if SLICE_NUM_HIGH > 0
>      bitmap_or(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> #endif
> }
> 
> I think that's pretty fine. If you have a singular hatred for ifdef in .c,
> then if() works just as well.
> 

To be honest, I tend to agree with you. Therefore, after a few words
with Michael, v5 gets rid of those obscure wrappers to come back to the 
initial (v1) approach which was to use 'if (SLICE_NUM_HIGH)'.
Behind the fact that it in my mind looks cleared in the code than using 
slice_bitmap_xxx() wrappers, it also has the advantage of significantly 
reducing the size of the patch, which is a must to be able to get it 
applied on stable.

Christophe