[PATCH v2 3/5] powerpc/mm: Allow more than 16 low slices

[Christophe Leroy <christophe.leroy@c-s.fr>]

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 resp. up to 1024 and 64
slices.

In order to override this limitation, this patch switches the
handling of low_slices to BITMAPs as done already for high_slices.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 v2: Usign slice_bitmap_xxx() macros instead of bitmap_xxx() functions.

 arch/powerpc/include/asm/book3s/64/mmu.h |   2 +-
 arch/powerpc/include/asm/mmu-8xx.h       |   2 +-
 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                  | 104 +++++++++++++++++--------------
 7 files changed, 74 insertions(+), 60 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index c9448e19847a..27e7e9732ea1 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -91,7 +91,7 @@ typedef struct {
 	struct npu_context *npu_context;
 
 #ifdef CONFIG_PPC_MM_SLICES
-	u64 low_slices_psize;	/* SLB page size encodings */
+	unsigned char low_slices_psize[8]; /* SLB page size encodings */
 	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 5f89b6010453..d669d0062da4 100644
--- a/arch/powerpc/include/asm/mmu-8xx.h
+++ b/arch/powerpc/include/asm/mmu-8xx.h
@@ -171,7 +171,7 @@ 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[8]; /* 16 slices */
 	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 23ac7fc0af23..0a6eea59a1c1 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[8];
 	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 d6597038931d..8e1566bf82b8 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -264,7 +264,8 @@ 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 3266b3326088..2f0c6b527a83 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1097,19 +1097,18 @@ 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 b617acf35836..fa6f7f63223c 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -43,7 +43,7 @@ static DEFINE_SPINLOCK(slice_convert_lock);
  * in 1TB size.
  */
 struct slice_mask {
-	u64 low_slices;
+	DECLARE_BITMAP(low_slices, SLICE_NUM_LOW);
 	DECLARE_BITMAP(high_slices, SLICE_NUM_HIGH);
 };
 
@@ -54,7 +54,8 @@ static void slice_print_mask(const char *label, struct slice_mask mask)
 {
 	if (!_slice_debug)
 		return;
-	pr_devel("%s low_slice: %*pbl\n", label, (int)SLICE_NUM_LOW, &mask.low_slices);
+	pr_devel("%s low_slice: %*pbl\n", label, (int)SLICE_NUM_LOW,
+		 mask.low_slices);
 	pr_devel("%s high_slice: %*pbl\n", label, (int)SLICE_NUM_HIGH, mask.high_slices);
 }
 
@@ -89,14 +90,17 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
 {
 	unsigned long end = start + len - 1;
 
-	ret->low_slices = 0;
+	slice_bitmap_zero(ret->low_slices, SLICE_NUM_LOW);
 	slice_bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
 
 	if (start <= SLICE_LOW_TOP) {
 		unsigned long mend = min(end, SLICE_LOW_TOP);
+		unsigned long start_index = GET_LOW_SLICE_INDEX(start);
+		unsigned long align_end = ALIGN(mend, (1UL << SLICE_LOW_SHIFT));
+		unsigned long count = GET_LOW_SLICE_INDEX(align_end) -
+				      start_index;
 
-		ret->low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
-			- (1u << GET_LOW_SLICE_INDEX(start));
+		slice_bitmap_set(ret->low_slices, start_index, count);
 	}
 
 	if ((start + len) > SLICE_LOW_TOP) {
@@ -144,12 +148,12 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
 {
 	unsigned long i;
 
-	ret->low_slices = 0;
+	slice_bitmap_zero(ret->low_slices, SLICE_NUM_LOW);
 	slice_bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
 
 	for (i = 0; i < SLICE_NUM_LOW; i++)
 		if (!slice_low_has_vma(mm, i))
-			ret->low_slices |= 1u << i;
+			__set_bit(i, ret->low_slices);
 
 	if (high_limit <= SLICE_LOW_TOP)
 		return;
@@ -162,18 +166,20 @@ 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->low_slices, SLICE_NUM_LOW);
 	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)
-			ret->low_slices |= 1u << i;
+	for (i = 0; i < SLICE_NUM_LOW; i++) {
+		mask_index = i & 0x1;
+		index = i >> 1;
+		if (((lpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
+			__set_bit(i, ret->low_slices);
+	}
 
 	if (high_limit <= SLICE_LOW_TOP)
 		return;
@@ -190,6 +196,7 @@ static void slice_mask_for_size(struct mm_struct *mm, int psize, struct slice_ma
 static int slice_check_fit(struct mm_struct *mm,
 			   struct slice_mask mask, struct slice_mask available)
 {
+	DECLARE_BITMAP(result_low, SLICE_NUM_LOW);
 	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
 	/*
 	 * Make sure we just do bit compare only to the max
@@ -197,11 +204,13 @@ static int slice_check_fit(struct mm_struct *mm,
 	 */
 	unsigned long slice_count = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
 
+	slice_bitmap_and(result_low, mask.low_slices,
+			 available.low_slices, SLICE_NUM_LOW);
 	slice_bitmap_and(result, mask.high_slices,
 			 available.high_slices, slice_count);
 
-	return (mask.low_slices & available.low_slices) == mask.low_slices &&
-		slice_bitmap_equal(result, mask.high_slices, slice_count));
+	return slice_bitmap_equal(result_low, mask.low_slices, SLICE_NUM_LOW) &&
+	       slice_bitmap_equal(result, mask.high_slices, slice_count);
 }
 
 static void slice_flush_segments(void *parm)
@@ -225,8 +234,7 @@ 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);
@@ -238,13 +246,14 @@ static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psiz
 	spin_lock_irqsave(&slice_convert_lock, flags);
 
 	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;
+	for (i = 0; i < SLICE_NUM_LOW; i++) {
+		mask_index = i & 0x1;
+		index = i >> 1;
+		if (test_bit(i, mask.low_slices))
+			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++) {
@@ -281,7 +290,7 @@ static bool slice_scan_available(unsigned long addr,
 	if (addr <= SLICE_LOW_TOP) {
 		slice = GET_LOW_SLICE_INDEX(addr);
 		*boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
-		return !!(available.low_slices & (1u << slice));
+		return !!test_bit(slice, available.low_slices);
 	} else {
 		slice = GET_HIGH_SLICE_INDEX(addr);
 		*boundary_addr = (slice + end) ?
@@ -409,7 +418,8 @@ 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;
+	slice_bitmap_or(dst->low_slices, dst->low_slices, src->low_slices,
+			SLICE_NUM_LOW);
 	slice_bitmap_or(result, dst->high_slices, src->high_slices,
 			SLICE_NUM_HIGH);
 	slice_bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
@@ -419,7 +429,8 @@ static inline void slice_andnot_mask(struct slice_mask *dst, struct slice_mask *
 {
 	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
 
-	dst->low_slices &= ~src->low_slices;
+	slice_bitmap_andnot(dst->low_slices, dst->low_slices, src->low_slices,
+			    SLICE_NUM_LOW);
 
 	slice_bitmap_andnot(result, dst->high_slices, src->high_slices,
 			    SLICE_NUM_HIGH);
@@ -470,14 +481,14 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 	/*
 	 * init different masks
 	 */
-	mask.low_slices = 0;
+	slice_bitmap_zero(mask.low_slices, SLICE_NUM_LOW);
 	slice_bitmap_zero(mask.high_slices, SLICE_NUM_HIGH);
 
 	/* silence stupid warning */;
-	potential_mask.low_slices = 0;
+	slice_bitmap_zero(potential_mask.low_slices, SLICE_NUM_LOW);
 	slice_bitmap_zero(potential_mask.high_slices, SLICE_NUM_HIGH);
 
-	compat_mask.low_slices = 0;
+	slice_bitmap_zero(compat_mask.low_slices, SLICE_NUM_LOW);
 	slice_bitmap_zero(compat_mask.high_slices, SLICE_NUM_HIGH);
 
 	/* Sanity checks */
@@ -616,7 +627,7 @@ 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 ||
+	if (!slice_bitmap_empty(mask.low_slices, SLICE_NUM_LOW) ||
 	    !slice_bitmap_empty(mask.high_slices, SLICE_NUM_HIGH)) {
 		slice_convert(mm, mask, psize);
 		if (psize > MMU_PAGE_BASE)
@@ -649,7 +660,7 @@ 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;
 
 	/*
@@ -663,15 +674,14 @@ 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);
 
@@ -692,8 +702,8 @@ 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;
 
@@ -711,12 +721,14 @@ 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