[PATCH v4 1/5] powerpc/mm/slice: Remove intermediate bitmap copy

[PATCH v4 1/5] powerpc/mm/slice: Remove intermediate bitmap copy

[Christophe Leroy]

bitmap_or() and bitmap_andnot() can work properly with dst identical
to src1 or src2. There is no need of an intermediate result bitmap
that is copied back to dst in a second step.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 v2: New in v2
 v3: patch moved up front of the serie to avoid ephemeral slice_bitmap_copy() function in following patch
 v4: No change

 arch/powerpc/mm/slice.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 23ec2c5e3b78..98b53d48968f 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -388,21 +388,17 @@ 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)
 {
-	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
-
 	dst->low_slices |= src->low_slices;
-	bitmap_or(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
-	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
+	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)
 {
-	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
-
 	dst->low_slices &= ~src->low_slices;
 
-	bitmap_andnot(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
-	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
+	bitmap_andnot(dst->high_slices, dst->high_slices, src->high_slices,
+		      SLICE_NUM_HIGH);
 }
 
 #ifdef CONFIG_PPC_64K_PAGES
-- 
2.13.3

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

[Christophe Leroy]

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

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

[PATCH v4 3/5] powerpc/mm/slice: Fix hugepage allocation at hint address on 8xx

[Christophe Leroy]

On the 8xx, the page size is set in the PMD entry and applies to
all pages of the page table pointed by the said PMD entry.

When an app has some regular pages allocated (e.g. see below) and tries
to mmap() a huge page at a hint address covered by the same PMD entry,
the kernel accepts the hint allthough the 8xx cannot handle different
page sizes in the same PMD entry.

10000000-10001000 r-xp 00000000 00:0f 2597 /root/malloc
10010000-10011000 rwxp 00000000 00:0f 2597 /root/malloc

mmap(0x10080000, 524288, PROT_READ|PROT_WRITE,
     MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0) = 0x10080000

This results the app remaining forever in do_page_fault()/hugetlb_fault()
and when interrupting that app, we get the following warning:

[162980.035629] WARNING: CPU: 0 PID: 2777 at arch/powerpc/mm/hugetlbpage.c:354 hugetlb_free_pgd_range+0xc8/0x1e4
[162980.035699] CPU: 0 PID: 2777 Comm: malloc Tainted: G W       4.14.6 #85
[162980.035744] task: c67e2c00 task.stack: c668e000
[162980.035783] NIP:  c000fe18 LR: c00e1eec CTR: c00f90c0
[162980.035830] REGS: c668fc20 TRAP: 0700   Tainted: G W        (4.14.6)
[162980.035854] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 24044224 XER: 20000000
[162980.036003]
[162980.036003] GPR00: c00e1eec c668fcd0 c67e2c00 00000010 c6869410 10080000 00000000 77fb4000
[162980.036003] GPR08: ffff0001 0683c001 00000000 ffffff80 44028228 10018a34 00004008 418004fc
[162980.036003] GPR16: c668e000 00040100 c668e000 c06c0000 c668fe78 c668e000 c6835ba0 c668fd48
[162980.036003] GPR24: 00000000 73ffffff 74000000 00000001 77fb4000 100fffff 10100000 10100000
[162980.036743] NIP [c000fe18] hugetlb_free_pgd_range+0xc8/0x1e4
[162980.036839] LR [c00e1eec] free_pgtables+0x12c/0x150
[162980.036861] Call Trace:
[162980.036939] [c668fcd0] [c00f0774] unlink_anon_vmas+0x1c4/0x214 (unreliable)
[162980.037040] [c668fd10] [c00e1eec] free_pgtables+0x12c/0x150
[162980.037118] [c668fd40] [c00eabac] exit_mmap+0xe8/0x1b4
[162980.037210] [c668fda0] [c0019710] mmput.part.9+0x20/0xd8
[162980.037301] [c668fdb0] [c001ecb0] do_exit+0x1f0/0x93c
[162980.037386] [c668fe00] [c001f478] do_group_exit+0x40/0xcc
[162980.037479] [c668fe10] [c002a76c] get_signal+0x47c/0x614
[162980.037570] [c668fe70] [c0007840] do_signal+0x54/0x244
[162980.037654] [c668ff30] [c0007ae8] do_notify_resume+0x34/0x88
[162980.037744] [c668ff40] [c000dae8] do_user_signal+0x74/0xc4
[162980.037781] Instruction dump:
[162980.037821] 7fdff378 81370000 54a3463a 80890020 7d24182e 7c841a14 712a0004 4082ff94
[162980.038014] 2f890000 419e0010 712a0ff0 408200e0 <0fe00000> 54a9000a 7f984840 419d0094
[162980.038216] ---[ end trace c0ceeca8e7a5800a ]---
[162980.038754] BUG: non-zero nr_ptes on freeing mm: 1
[162985.363322] BUG: non-zero nr_ptes on freeing mm: -1

In order to fix this, this patch uses the address space "slices"
implemented for BOOK3S/64 and enhanced to support PPC32 by the
preceding patch.

This patch modifies the context.id on the 8xx to be in the range
[1:16] instead of [0:15] in order to identify context.id == 0 as
not initialised contexts as done on BOOK3S

This patch activates CONFIG_PPC_MM_SLICES when CONFIG_HUGETLB_PAGE is
selected for the 8xx

Alltough we could in theory have as many slices as PMD entries, the
current slices implementation limits the number of low slices to 16.
This limitation is not preventing us to fix the initial issue allthough
it is suboptimal. It will be cured in a subsequent patch.

Fixes: 4b91428699477 ("powerpc/8xx: Implement support of hugepages")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 v2: First patch of v1 serie split in two parts
 v3: No changes
 v4: No changes

 arch/powerpc/include/asm/mmu-8xx.h     |  6 ++++++
 arch/powerpc/kernel/setup-common.c     |  2 ++
 arch/powerpc/mm/8xx_mmu.c              |  2 +-
 arch/powerpc/mm/hugetlbpage.c          |  2 ++
 arch/powerpc/mm/mmu_context_nohash.c   | 18 ++++++++++++++++--
 arch/powerpc/platforms/Kconfig.cputype |  1 +
 6 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu-8xx.h b/arch/powerpc/include/asm/mmu-8xx.h
index 2f806e329648..b324ab46d838 100644
--- a/arch/powerpc/include/asm/mmu-8xx.h
+++ b/arch/powerpc/include/asm/mmu-8xx.h
@@ -191,6 +191,12 @@ typedef struct {
 	unsigned int id;
 	unsigned int active;
 	unsigned long vdso_base;
+#ifdef CONFIG_PPC_MM_SLICES
+	u16 user_psize;		/* page size index */
+	u64 low_slices_psize;	/* page size encodings */
+	unsigned char high_slices_psize[0];
+	unsigned long slb_addr_limit;
+#endif
 } mm_context_t;
 
 #define PHYS_IMMR_BASE (mfspr(SPRN_IMMR) & 0xfff80000)
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index d73ec518ef80..a6002f9449b1 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -919,6 +919,8 @@ void __init setup_arch(char **cmdline_p)
 #ifdef CONFIG_PPC64
 	if (!radix_enabled())
 		init_mm.context.slb_addr_limit = DEFAULT_MAP_WINDOW_USER64;
+#elif defined(CONFIG_PPC_8xx)
+	init_mm.context.slb_addr_limit = DEFAULT_MAP_WINDOW;
 #else
 #error	"context.addr_limit not initialized."
 #endif
diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c
index 849f50cd62f2..cf77d755246d 100644
--- a/arch/powerpc/mm/8xx_mmu.c
+++ b/arch/powerpc/mm/8xx_mmu.c
@@ -192,7 +192,7 @@ void set_context(unsigned long id, pgd_t *pgd)
 	mtspr(SPRN_M_TW, __pa(pgd) - offset);
 
 	/* Update context */
-	mtspr(SPRN_M_CASID, id);
+	mtspr(SPRN_M_CASID, id - 1);
 	/* sync */
 	mb();
 }
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 876da2bc1796..590be3fa0ce2 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -553,9 +553,11 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 	struct hstate *hstate = hstate_file(file);
 	int mmu_psize = shift_to_mmu_psize(huge_page_shift(hstate));
 
+#ifdef CONFIG_PPC_RADIX_MMU
 	if (radix_enabled())
 		return radix__hugetlb_get_unmapped_area(file, addr, len,
 						       pgoff, flags);
+#endif
 	return slice_get_unmapped_area(addr, len, flags, mmu_psize, 1);
 }
 #endif
diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c
index 4554d6527682..d98f7e5c141b 100644
--- a/arch/powerpc/mm/mmu_context_nohash.c
+++ b/arch/powerpc/mm/mmu_context_nohash.c
@@ -331,6 +331,20 @@ int init_new_context(struct task_struct *t, struct mm_struct *mm)
 {
 	pr_hard("initing context for mm @%p\n", mm);
 
+#ifdef	CONFIG_PPC_MM_SLICES
+	if (!mm->context.slb_addr_limit)
+		mm->context.slb_addr_limit = DEFAULT_MAP_WINDOW;
+
+	/*
+	 * We have MMU_NO_CONTEXT set to be ~0. Hence check
+	 * explicitly against context.id == 0. This ensures that we properly
+	 * initialize context slice details for newly allocated mm's (which will
+	 * have id == 0) and don't alter context slice inherited via fork (which
+	 * will have id != 0).
+	 */
+	if (mm->context.id == 0)
+		slice_set_user_psize(mm, mmu_virtual_psize);
+#endif
 	mm->context.id = MMU_NO_CONTEXT;
 	mm->context.active = 0;
 	return 0;
@@ -428,8 +442,8 @@ void __init mmu_context_init(void)
 	 *      -- BenH
 	 */
 	if (mmu_has_feature(MMU_FTR_TYPE_8xx)) {
-		first_context = 0;
-		last_context = 15;
+		first_context = 1;
+		last_context = 16;
 		no_selective_tlbil = true;
 	} else if (mmu_has_feature(MMU_FTR_TYPE_47x)) {
 		first_context = 1;
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index a429d859f15d..5a8b1bf1e819 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -326,6 +326,7 @@ config PPC_BOOK3E_MMU
 config PPC_MM_SLICES
 	bool
 	default y if PPC_BOOK3S_64
+	default y if PPC_8xx && HUGETLB_PAGE
 	default n
 
 config PPC_HAVE_PMU_SUPPORT
-- 
2.13.3

[PATCH v4 4/5] powerpc/mm/slice: Allow up to 64 low slices

[Christophe Leroy]

While the implementation of the "slices" address space allows
a significant amount of high slices, it limits the number of
low slices to 16 due to the use of a single u64 low_slices_psize
element in struct mm_context_t

On the 8xx, the minimum slice size is the size of the area
covered by a single PMD entry, ie 4M in 4K pages mode and 64M in
16K pages mode. This means we could have at least 64 slices.

In order to override this limitation, this patch switches the
handling of low_slices_psize to char array as done already for
high_slices_psize.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 v2: Using slice_bitmap_xxx() macros instead of bitmap_xxx() functions.
 v3: keep low_slices as a u64, this allows 64 slices which is enough.
 v4: Moved the 8xx specifics to next patch
 
 arch/powerpc/include/asm/book3s/64/mmu.h |  3 +-
 arch/powerpc/include/asm/mmu-8xx.h       |  7 +++-
 arch/powerpc/include/asm/paca.h          |  2 +-
 arch/powerpc/kernel/paca.c               |  3 +-
 arch/powerpc/mm/hash_utils_64.c          | 13 ++++----
 arch/powerpc/mm/slb_low.S                |  8 +++--
 arch/powerpc/mm/slice.c                  | 57 +++++++++++++++++---------------
 7 files changed, 52 insertions(+), 41 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index 0abeb0e2d616..bef6e39ed63a 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -91,7 +91,8 @@ typedef struct {
 	struct npu_context *npu_context;
 
 #ifdef CONFIG_PPC_MM_SLICES
-	u64 low_slices_psize;	/* SLB page size encodings */
+	 /* SLB page size encodings*/
+	unsigned char low_slices_psize[BITS_PER_LONG / BITS_PER_BYTE];
 	unsigned char high_slices_psize[SLICE_ARRAY_SIZE];
 	unsigned long slb_addr_limit;
 #else
diff --git a/arch/powerpc/include/asm/mmu-8xx.h b/arch/powerpc/include/asm/mmu-8xx.h
index b324ab46d838..d3d7e79140c6 100644
--- a/arch/powerpc/include/asm/mmu-8xx.h
+++ b/arch/powerpc/include/asm/mmu-8xx.h
@@ -186,6 +186,11 @@
 #define M_APG2		0x00000040
 #define M_APG3		0x00000060
 
+#ifdef CONFIG_PPC_MM_SLICES
+#include <asm/nohash/32/slice.h>
+#define SLICE_ARRAY_SIZE	(1 << (32 - SLICE_LOW_SHIFT - 1))
+#endif
+
 #ifndef __ASSEMBLY__
 typedef struct {
 	unsigned int id;
@@ -193,7 +198,7 @@ typedef struct {
 	unsigned long vdso_base;
 #ifdef CONFIG_PPC_MM_SLICES
 	u16 user_psize;		/* page size index */
-	u64 low_slices_psize;	/* page size encodings */
+	unsigned char low_slices_psize[SLICE_ARRAY_SIZE];
 	unsigned char high_slices_psize[0];
 	unsigned long slb_addr_limit;
 #endif
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index b62c31037cad..d2bf71dddbef 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -141,7 +141,7 @@ struct paca_struct {
 #ifdef CONFIG_PPC_BOOK3S
 	mm_context_id_t mm_ctx_id;
 #ifdef CONFIG_PPC_MM_SLICES
-	u64 mm_ctx_low_slices_psize;
+	unsigned char mm_ctx_low_slices_psize[BITS_PER_LONG / BITS_PER_BYTE];
 	unsigned char mm_ctx_high_slices_psize[SLICE_ARRAY_SIZE];
 	unsigned long mm_ctx_slb_addr_limit;
 #else
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index 95ffedf14885..2fd563d05831 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -265,7 +265,8 @@ void copy_mm_to_paca(struct mm_struct *mm)
 #ifdef CONFIG_PPC_MM_SLICES
 	VM_BUG_ON(!mm->context.slb_addr_limit);
 	get_paca()->mm_ctx_slb_addr_limit = mm->context.slb_addr_limit;
-	get_paca()->mm_ctx_low_slices_psize = context->low_slices_psize;
+	memcpy(&get_paca()->mm_ctx_low_slices_psize,
+	       &context->low_slices_psize, sizeof(context->low_slices_psize));
 	memcpy(&get_paca()->mm_ctx_high_slices_psize,
 	       &context->high_slices_psize, TASK_SLICE_ARRAY_SZ(mm));
 #else /* CONFIG_PPC_MM_SLICES */
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 7d07c7e17db6..2c1f4dac1098 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1109,19 +1109,18 @@ unsigned int hash_page_do_lazy_icache(unsigned int pp, pte_t pte, int trap)
 #ifdef CONFIG_PPC_MM_SLICES
 static unsigned int get_paca_psize(unsigned long addr)
 {
-	u64 lpsizes;
-	unsigned char *hpsizes;
+	unsigned char *psizes;
 	unsigned long index, mask_index;
 
 	if (addr < SLICE_LOW_TOP) {
-		lpsizes = get_paca()->mm_ctx_low_slices_psize;
+		psizes = get_paca()->mm_ctx_low_slices_psize;
 		index = GET_LOW_SLICE_INDEX(addr);
-		return (lpsizes >> (index * 4)) & 0xF;
+	} else {
+		psizes = get_paca()->mm_ctx_high_slices_psize;
+		index = GET_HIGH_SLICE_INDEX(addr);
 	}
-	hpsizes = get_paca()->mm_ctx_high_slices_psize;
-	index = GET_HIGH_SLICE_INDEX(addr);
 	mask_index = index & 0x1;
-	return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xF;
+	return (psizes[index >> 1] >> (mask_index * 4)) & 0xF;
 }
 
 #else
diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S
index 2cf5ef3fc50d..2c7c717fd2ea 100644
--- a/arch/powerpc/mm/slb_low.S
+++ b/arch/powerpc/mm/slb_low.S
@@ -200,10 +200,12 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_1T_SEGMENT)
 5:
 	/*
 	 * Handle lpsizes
-	 * r9 is get_paca()->context.low_slices_psize, r11 is index
+	 * r9 is get_paca()->context.low_slices_psize[index], r11 is mask_index
 	 */
-	ld	r9,PACALOWSLICESPSIZE(r13)
-	mr	r11,r10
+	srdi    r11,r10,1 /* index */
+	addi	r9,r11,PACALOWSLICESPSIZE
+	lbzx	r9,r13,r9		/* r9 is lpsizes[r11] */
+	rldicl	r11,r10,0,63		/* r11 = r10 & 0x1 */
 6:
 	sldi	r11,r11,2  /* index * 4 */
 	/* Extract the psize and multiply to get an array offset */
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 549704dfa777..3d573a038d42 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -148,18 +148,20 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
 static void slice_mask_for_size(struct mm_struct *mm, int psize, struct slice_mask *ret,
 				unsigned long high_limit)
 {
-	unsigned char *hpsizes;
+	unsigned char *hpsizes, *lpsizes;
 	int index, mask_index;
 	unsigned long i;
-	u64 lpsizes;
 
 	ret->low_slices = 0;
 	slice_bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
 
 	lpsizes = mm->context.low_slices_psize;
-	for (i = 0; i < SLICE_NUM_LOW; i++)
-		if (((lpsizes >> (i * 4)) & 0xf) == psize)
+	for (i = 0; i < SLICE_NUM_LOW; i++) {
+		mask_index = i & 0x1;
+		index = i >> 1;
+		if (((lpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
 			ret->low_slices |= 1u << i;
+	}
 
 	if (high_limit <= SLICE_LOW_TOP)
 		return;
@@ -211,8 +213,7 @@ static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psiz
 {
 	int index, mask_index;
 	/* Write the new slice psize bits */
-	unsigned char *hpsizes;
-	u64 lpsizes;
+	unsigned char *hpsizes, *lpsizes;
 	unsigned long i, flags;
 
 	slice_dbg("slice_convert(mm=%p, psize=%d)\n", mm, psize);
@@ -225,12 +226,13 @@ static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psiz
 
 	lpsizes = mm->context.low_slices_psize;
 	for (i = 0; i < SLICE_NUM_LOW; i++)
-		if (mask.low_slices & (1u << i))
-			lpsizes = (lpsizes & ~(0xful << (i * 4))) |
-				(((unsigned long)psize) << (i * 4));
-
-	/* Assign the value back */
-	mm->context.low_slices_psize = lpsizes;
+		if (mask.low_slices & (1u << i)) {
+			mask_index = i & 0x1;
+			index = i >> 1;
+			lpsizes[index] = (lpsizes[index] &
+					  ~(0xf << (mask_index * 4))) |
+				(((unsigned long)psize) << (mask_index * 4));
+		}
 
 	hpsizes = mm->context.high_slices_psize;
 	for (i = 0; i < GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit); i++) {
@@ -629,7 +631,7 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 
 unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
 {
-	unsigned char *hpsizes;
+	unsigned char *psizes;
 	int index, mask_index;
 
 	/*
@@ -643,15 +645,14 @@ unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
 #endif
 	}
 	if (addr < SLICE_LOW_TOP) {
-		u64 lpsizes;
-		lpsizes = mm->context.low_slices_psize;
+		psizes = mm->context.low_slices_psize;
 		index = GET_LOW_SLICE_INDEX(addr);
-		return (lpsizes >> (index * 4)) & 0xf;
+	} else {
+		psizes = mm->context.high_slices_psize;
+		index = GET_HIGH_SLICE_INDEX(addr);
 	}
-	hpsizes = mm->context.high_slices_psize;
-	index = GET_HIGH_SLICE_INDEX(addr);
 	mask_index = index & 0x1;
-	return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xf;
+	return (psizes[index >> 1] >> (mask_index * 4)) & 0xf;
 }
 EXPORT_SYMBOL_GPL(get_slice_psize);
 
@@ -672,8 +673,8 @@ EXPORT_SYMBOL_GPL(get_slice_psize);
 void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
 {
 	int index, mask_index;
-	unsigned char *hpsizes;
-	unsigned long flags, lpsizes;
+	unsigned char *hpsizes, *lpsizes;
+	unsigned long flags;
 	unsigned int old_psize;
 	int i;
 
@@ -691,12 +692,14 @@ void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
 	wmb();
 
 	lpsizes = mm->context.low_slices_psize;
-	for (i = 0; i < SLICE_NUM_LOW; i++)
-		if (((lpsizes >> (i * 4)) & 0xf) == old_psize)
-			lpsizes = (lpsizes & ~(0xful << (i * 4))) |
-				(((unsigned long)psize) << (i * 4));
-	/* Assign the value back */
-	mm->context.low_slices_psize = lpsizes;
+	for (i = 0; i < SLICE_NUM_LOW; i++) {
+		mask_index = i & 0x1;
+		index = i >> 1;
+		if (((lpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)
+			lpsizes[index] = (lpsizes[index] &
+					  ~(0xf << (mask_index * 4))) |
+				(((unsigned long)psize) << (mask_index * 4));
+	}
 
 	hpsizes = mm->context.high_slices_psize;
 	for (i = 0; i < SLICE_NUM_HIGH; i++) {
-- 
2.13.3

[PATCH v4 5/5] powerpc/8xx: Increase number of slices to 64

[Christophe Leroy]

On the 8xx, the minimum slice size is the size of the area
covered by a single PMD entry, ie 4M in 4K pages mode and 64M in
16K pages mode.

This patch increases the number of slices from 16 to 64 on the 8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 v4: New
 
 arch/powerpc/include/asm/nohash/32/slice.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/nohash/32/slice.h b/arch/powerpc/include/asm/nohash/32/slice.h
index bcb4924f7d22..3deaaea89473 100644
--- a/arch/powerpc/include/asm/nohash/32/slice.h
+++ b/arch/powerpc/include/asm/nohash/32/slice.h
@@ -4,7 +4,7 @@
 
 #ifdef CONFIG_PPC_MM_SLICES
 
-#define SLICE_LOW_SHIFT		28
+#define SLICE_LOW_SHIFT		26	/* 64 slices */
 #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)
-- 
2.13.3

Re: [PATCH v4 1/5] powerpc/mm/slice: Remove intermediate bitmap copy

[Nicholas Piggin]

On Sat, 10 Feb 2018 13:54:25 +0100 (CET)
Christophe Leroy <christophe.leroy@c-s.fr> wrote:

> bitmap_or() and bitmap_andnot() can work properly with dst identical
> to src1 or src2. There is no need of an intermediate result bitmap
> that is copied back to dst in a second step.

Everyone seems to be working on the slice code all of a sudden. I
had the same change in my series I just posted, but I didn't notice
this one of yours earlier, and it's better split out, so this is
fine by me.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>  v2: New in v2
>  v3: patch moved up front of the serie to avoid ephemeral slice_bitmap_copy() function in following patch
>  v4: No change
> 
>  arch/powerpc/mm/slice.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> index 23ec2c5e3b78..98b53d48968f 100644
> --- a/arch/powerpc/mm/slice.c
> +++ b/arch/powerpc/mm/slice.c
> @@ -388,21 +388,17 @@ 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)
>  {
> -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
> -
>  	dst->low_slices |= src->low_slices;
> -	bitmap_or(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
> +	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)
>  {
> -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
> -
>  	dst->low_slices &= ~src->low_slices;
>  
> -	bitmap_andnot(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
> +	bitmap_andnot(dst->high_slices, dst->high_slices, src->high_slices,
> +		      SLICE_NUM_HIGH);
>  }
>  
>  #ifdef CONFIG_PPC_64K_PAGES

Re: [PATCH v4 1/5] powerpc/mm/slice: Remove intermediate bitmap copy

[Christophe LEROY]

Le 10/02/2018 à 15:43, Nicholas Piggin a écrit :
> On Sat, 10 Feb 2018 13:54:25 +0100 (CET)
> Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> 
>> bitmap_or() and bitmap_andnot() can work properly with dst identical
>> to src1 or src2. There is no need of an intermediate result bitmap
>> that is copied back to dst in a second step.
> 
> Everyone seems to be working on the slice code all of a sudden. I
> had the same change in my series I just posted, but I didn't notice
> this one of yours earlier, and it's better split out, so this is
> fine by me.

Thanks,

I had a quick look at your serie, it looks promising.

The main purpose of mine is to allow the use of slies on the 8xx in 
order to fix a hugepage related bug.

Your serie is performance oriented and seems nice, indeed I should have 
noticed that it was passing huge structures instead of pointers to 
subfunctions. I will look at your serie more in details next week.

Christophe


> 
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> 
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>> ---
>>   v2: New in v2
>>   v3: patch moved up front of the serie to avoid ephemeral slice_bitmap_copy() function in following patch
>>   v4: No change
>>
>>   arch/powerpc/mm/slice.c | 12 ++++--------
>>   1 file changed, 4 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
>> index 23ec2c5e3b78..98b53d48968f 100644
>> --- a/arch/powerpc/mm/slice.c
>> +++ b/arch/powerpc/mm/slice.c
>> @@ -388,21 +388,17 @@ 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)
>>   {
>> -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
>> -
>>   	dst->low_slices |= src->low_slices;
>> -	bitmap_or(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
>> -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
>> +	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)
>>   {
>> -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
>> -
>>   	dst->low_slices &= ~src->low_slices;
>>   
>> -	bitmap_andnot(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
>> -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
>> +	bitmap_andnot(dst->high_slices, dst->high_slices, src->high_slices,
>> +		      SLICE_NUM_HIGH);
>>   }
>>   
>>   #ifdef CONFIG_PPC_64K_PAGES

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

[Nicholas Piggin]

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

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

[Aneesh Kumar K.V]

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

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

[Nicholas Piggin]

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

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

[Aneesh Kumar K.V]

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

Re: [PATCH v4 4/5] powerpc/mm/slice: Allow up to 64 low slices

[Aneesh Kumar K.V]

Christophe Leroy <christophe.leroy@c-s.fr> writes:

> While the implementation of the "slices" address space allows
> a significant amount of high slices, it limits the number of
> low slices to 16 due to the use of a single u64 low_slices_psize
> element in struct mm_context_t
>
> On the 8xx, the minimum slice size is the size of the area
> covered by a single PMD entry, ie 4M in 4K pages mode and 64M in
> 16K pages mode. This means we could have at least 64 slices.
>
> In order to override this limitation, this patch switches the
> handling of low_slices_psize to char array as done already for
> high_slices_psize.
>

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

> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>  v2: Using slice_bitmap_xxx() macros instead of bitmap_xxx() functions.
>  v3: keep low_slices as a u64, this allows 64 slices which is enough.
>  v4: Moved the 8xx specifics to next patch
>  
>  arch/powerpc/include/asm/book3s/64/mmu.h |  3 +-
>  arch/powerpc/include/asm/mmu-8xx.h       |  7 +++-
>  arch/powerpc/include/asm/paca.h          |  2 +-
>  arch/powerpc/kernel/paca.c               |  3 +-
>  arch/powerpc/mm/hash_utils_64.c          | 13 ++++----
>  arch/powerpc/mm/slb_low.S                |  8 +++--
>  arch/powerpc/mm/slice.c                  | 57 +++++++++++++++++---------------
>  7 files changed, 52 insertions(+), 41 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
> index 0abeb0e2d616..bef6e39ed63a 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu.h
> @@ -91,7 +91,8 @@ typedef struct {
>  	struct npu_context *npu_context;
>  
>  #ifdef CONFIG_PPC_MM_SLICES
> -	u64 low_slices_psize;	/* SLB page size encodings */
> +	 /* SLB page size encodings*/
> +	unsigned char low_slices_psize[BITS_PER_LONG / BITS_PER_BYTE];
>  	unsigned char high_slices_psize[SLICE_ARRAY_SIZE];
>  	unsigned long slb_addr_limit;
>  #else
> diff --git a/arch/powerpc/include/asm/mmu-8xx.h b/arch/powerpc/include/asm/mmu-8xx.h
> index b324ab46d838..d3d7e79140c6 100644
> --- a/arch/powerpc/include/asm/mmu-8xx.h
> +++ b/arch/powerpc/include/asm/mmu-8xx.h
> @@ -186,6 +186,11 @@
>  #define M_APG2		0x00000040
>  #define M_APG3		0x00000060
>  
> +#ifdef CONFIG_PPC_MM_SLICES
> +#include <asm/nohash/32/slice.h>
> +#define SLICE_ARRAY_SIZE	(1 << (32 - SLICE_LOW_SHIFT - 1))
> +#endif
> +
>  #ifndef __ASSEMBLY__
>  typedef struct {
>  	unsigned int id;
> @@ -193,7 +198,7 @@ typedef struct {
>  	unsigned long vdso_base;
>  #ifdef CONFIG_PPC_MM_SLICES
>  	u16 user_psize;		/* page size index */
> -	u64 low_slices_psize;	/* page size encodings */
> +	unsigned char low_slices_psize[SLICE_ARRAY_SIZE];
>  	unsigned char high_slices_psize[0];
>  	unsigned long slb_addr_limit;
>  #endif
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index b62c31037cad..d2bf71dddbef 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -141,7 +141,7 @@ struct paca_struct {
>  #ifdef CONFIG_PPC_BOOK3S
>  	mm_context_id_t mm_ctx_id;
>  #ifdef CONFIG_PPC_MM_SLICES
> -	u64 mm_ctx_low_slices_psize;
> +	unsigned char mm_ctx_low_slices_psize[BITS_PER_LONG / BITS_PER_BYTE];
>  	unsigned char mm_ctx_high_slices_psize[SLICE_ARRAY_SIZE];
>  	unsigned long mm_ctx_slb_addr_limit;
>  #else
> diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
> index 95ffedf14885..2fd563d05831 100644
> --- a/arch/powerpc/kernel/paca.c
> +++ b/arch/powerpc/kernel/paca.c
> @@ -265,7 +265,8 @@ void copy_mm_to_paca(struct mm_struct *mm)
>  #ifdef CONFIG_PPC_MM_SLICES
>  	VM_BUG_ON(!mm->context.slb_addr_limit);
>  	get_paca()->mm_ctx_slb_addr_limit = mm->context.slb_addr_limit;
> -	get_paca()->mm_ctx_low_slices_psize = context->low_slices_psize;
> +	memcpy(&get_paca()->mm_ctx_low_slices_psize,
> +	       &context->low_slices_psize, sizeof(context->low_slices_psize));
>  	memcpy(&get_paca()->mm_ctx_high_slices_psize,
>  	       &context->high_slices_psize, TASK_SLICE_ARRAY_SZ(mm));
>  #else /* CONFIG_PPC_MM_SLICES */
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 7d07c7e17db6..2c1f4dac1098 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -1109,19 +1109,18 @@ unsigned int hash_page_do_lazy_icache(unsigned int pp, pte_t pte, int trap)
>  #ifdef CONFIG_PPC_MM_SLICES
>  static unsigned int get_paca_psize(unsigned long addr)
>  {
> -	u64 lpsizes;
> -	unsigned char *hpsizes;
> +	unsigned char *psizes;
>  	unsigned long index, mask_index;
>  
>  	if (addr < SLICE_LOW_TOP) {
> -		lpsizes = get_paca()->mm_ctx_low_slices_psize;
> +		psizes = get_paca()->mm_ctx_low_slices_psize;
>  		index = GET_LOW_SLICE_INDEX(addr);
> -		return (lpsizes >> (index * 4)) & 0xF;
> +	} else {
> +		psizes = get_paca()->mm_ctx_high_slices_psize;
> +		index = GET_HIGH_SLICE_INDEX(addr);
>  	}
> -	hpsizes = get_paca()->mm_ctx_high_slices_psize;
> -	index = GET_HIGH_SLICE_INDEX(addr);
>  	mask_index = index & 0x1;
> -	return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xF;
> +	return (psizes[index >> 1] >> (mask_index * 4)) & 0xF;
>  }
>  
>  #else
> diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S
> index 2cf5ef3fc50d..2c7c717fd2ea 100644
> --- a/arch/powerpc/mm/slb_low.S
> +++ b/arch/powerpc/mm/slb_low.S
> @@ -200,10 +200,12 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_1T_SEGMENT)
>  5:
>  	/*
>  	 * Handle lpsizes
> -	 * r9 is get_paca()->context.low_slices_psize, r11 is index
> +	 * r9 is get_paca()->context.low_slices_psize[index], r11 is mask_index
>  	 */
> -	ld	r9,PACALOWSLICESPSIZE(r13)
> -	mr	r11,r10
> +	srdi    r11,r10,1 /* index */
> +	addi	r9,r11,PACALOWSLICESPSIZE
> +	lbzx	r9,r13,r9		/* r9 is lpsizes[r11] */
> +	rldicl	r11,r10,0,63		/* r11 = r10 & 0x1 */
>  6:
>  	sldi	r11,r11,2  /* index * 4 */
>  	/* Extract the psize and multiply to get an array offset */
> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> index 549704dfa777..3d573a038d42 100644
> --- a/arch/powerpc/mm/slice.c
> +++ b/arch/powerpc/mm/slice.c
> @@ -148,18 +148,20 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
>  static void slice_mask_for_size(struct mm_struct *mm, int psize, struct slice_mask *ret,
>  				unsigned long high_limit)
>  {
> -	unsigned char *hpsizes;
> +	unsigned char *hpsizes, *lpsizes;
>  	int index, mask_index;
>  	unsigned long i;
> -	u64 lpsizes;
>  
>  	ret->low_slices = 0;
>  	slice_bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
>  
>  	lpsizes = mm->context.low_slices_psize;
> -	for (i = 0; i < SLICE_NUM_LOW; i++)
> -		if (((lpsizes >> (i * 4)) & 0xf) == psize)
> +	for (i = 0; i < SLICE_NUM_LOW; i++) {
> +		mask_index = i & 0x1;
> +		index = i >> 1;
> +		if (((lpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
>  			ret->low_slices |= 1u << i;
> +	}
>  
>  	if (high_limit <= SLICE_LOW_TOP)
>  		return;
> @@ -211,8 +213,7 @@ static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psiz
>  {
>  	int index, mask_index;
>  	/* Write the new slice psize bits */
> -	unsigned char *hpsizes;
> -	u64 lpsizes;
> +	unsigned char *hpsizes, *lpsizes;
>  	unsigned long i, flags;
>  
>  	slice_dbg("slice_convert(mm=%p, psize=%d)\n", mm, psize);
> @@ -225,12 +226,13 @@ static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psiz
>  
>  	lpsizes = mm->context.low_slices_psize;
>  	for (i = 0; i < SLICE_NUM_LOW; i++)
> -		if (mask.low_slices & (1u << i))
> -			lpsizes = (lpsizes & ~(0xful << (i * 4))) |
> -				(((unsigned long)psize) << (i * 4));
> -
> -	/* Assign the value back */
> -	mm->context.low_slices_psize = lpsizes;
> +		if (mask.low_slices & (1u << i)) {
> +			mask_index = i & 0x1;
> +			index = i >> 1;
> +			lpsizes[index] = (lpsizes[index] &
> +					  ~(0xf << (mask_index * 4))) |
> +				(((unsigned long)psize) << (mask_index * 4));
> +		}
>  
>  	hpsizes = mm->context.high_slices_psize;
>  	for (i = 0; i < GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit); i++) {
> @@ -629,7 +631,7 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
>  
>  unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
>  {
> -	unsigned char *hpsizes;
> +	unsigned char *psizes;
>  	int index, mask_index;
>  
>  	/*
> @@ -643,15 +645,14 @@ unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
>  #endif
>  	}
>  	if (addr < SLICE_LOW_TOP) {
> -		u64 lpsizes;
> -		lpsizes = mm->context.low_slices_psize;
> +		psizes = mm->context.low_slices_psize;
>  		index = GET_LOW_SLICE_INDEX(addr);
> -		return (lpsizes >> (index * 4)) & 0xf;
> +	} else {
> +		psizes = mm->context.high_slices_psize;
> +		index = GET_HIGH_SLICE_INDEX(addr);
>  	}
> -	hpsizes = mm->context.high_slices_psize;
> -	index = GET_HIGH_SLICE_INDEX(addr);
>  	mask_index = index & 0x1;
> -	return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xf;
> +	return (psizes[index >> 1] >> (mask_index * 4)) & 0xf;
>  }
>  EXPORT_SYMBOL_GPL(get_slice_psize);
>  
> @@ -672,8 +673,8 @@ EXPORT_SYMBOL_GPL(get_slice_psize);
>  void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
>  {
>  	int index, mask_index;
> -	unsigned char *hpsizes;
> -	unsigned long flags, lpsizes;
> +	unsigned char *hpsizes, *lpsizes;
> +	unsigned long flags;
>  	unsigned int old_psize;
>  	int i;
>  
> @@ -691,12 +692,14 @@ void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
>  	wmb();
>  
>  	lpsizes = mm->context.low_slices_psize;
> -	for (i = 0; i < SLICE_NUM_LOW; i++)
> -		if (((lpsizes >> (i * 4)) & 0xf) == old_psize)
> -			lpsizes = (lpsizes & ~(0xful << (i * 4))) |
> -				(((unsigned long)psize) << (i * 4));
> -	/* Assign the value back */
> -	mm->context.low_slices_psize = lpsizes;
> +	for (i = 0; i < SLICE_NUM_LOW; i++) {
> +		mask_index = i & 0x1;
> +		index = i >> 1;
> +		if (((lpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)
> +			lpsizes[index] = (lpsizes[index] &
> +					  ~(0xf << (mask_index * 4))) |
> +				(((unsigned long)psize) << (mask_index * 4));
> +	}
>  
>  	hpsizes = mm->context.high_slices_psize;
>  	for (i = 0; i < SLICE_NUM_HIGH; i++) {
> -- 
> 2.13.3

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

[Christophe LEROY]

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