[PATCH] ppc64: Convert mm_context_t to a struct

From: David Gibson <david@gibson.dropbear.id.au>

Converts the mm_context_t on ppc64 to be a struct.  This lets us separate
the low_hpages flag into a separate field rather than folding it into the
actual context id.  That makes things neater, since the flag is
conceptually separate and has, for example, should be propogate across a
fork whereas the context ID obviously isn't.  The mm_context_id is the only
place to put arch-specific information in the mm_struct.

This patch will also make some interesting extensions to the hugepage
support much easier, such as allowing dynamic resizing of the hugepage
address space, or using special pagetables for hugepages.

3 files changed, 20 insertions, 14 deletions

diff --git a/include/asm-ppc64/mmu.h b/include/asm-ppc64/mmu.h
index 3ecacc7de85f..a68e47f717e7 100644
--- a/include/asm-ppc64/mmu.h
+++ b/include/asm-ppc64/mmu.h
@@ -18,15 +18,25 @@
 
 #ifndef __ASSEMBLY__
 
-/* Default "unsigned long" context */
-typedef unsigned long mm_context_t;
+/* Time to allow for more things here */
+typedef unsigned long mm_context_id_t;
+typedef struct {
+	mm_context_id_t id;
+#ifdef CONFIG_HUGETLB_PAGE
+	int low_hpages;
+#endif
+} mm_context_t;
 
 #ifdef CONFIG_HUGETLB_PAGE
-#define CONTEXT_LOW_HPAGES	(1UL<<63)
+#define KERNEL_LOW_HPAGES	.low_hpages = 0,
 #else
-#define CONTEXT_LOW_HPAGES	0
+#define KERNEL_LOW_HPAGES
 #endif
 
+#define KERNEL_CONTEXT(ea) ({ \
+		mm_context_t ctx = { .id = REGION_ID(ea), KERNEL_LOW_HPAGES}; \
+		ctx; })
+
 /*
  * Hardware Segment Lookaside Buffer Entry
  * This structure has been padded out to two 64b doublewords (actual SLBE's are
diff --git a/include/asm-ppc64/mmu_context.h b/include/asm-ppc64/mmu_context.h
index 57076c656f07..8be5b8d0a61b 100644
--- a/include/asm-ppc64/mmu_context.h
+++ b/include/asm-ppc64/mmu_context.h
@@ -52,7 +52,7 @@ struct mmu_context_queue_t {
 	long head;
 	long tail;
 	long size;
-	mm_context_t elements[LAST_USER_CONTEXT];
+	mm_context_id_t elements[LAST_USER_CONTEXT];
 };
 
 extern struct mmu_context_queue_t mmu_context_queue;
@@ -83,7 +83,6 @@ init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 	long head;
 	unsigned long flags;
 	/* This does the right thing across a fork (I hope) */
-	unsigned long low_hpages = mm->context & CONTEXT_LOW_HPAGES;
 
 	spin_lock_irqsave(&mmu_context_queue.lock, flags);
 
@@ -93,8 +92,7 @@ init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 	}
 
 	head = mmu_context_queue.head;
-	mm->context = mmu_context_queue.elements[head];
-	mm->context |= low_hpages;
+	mm->context.id = mmu_context_queue.elements[head];
 
 	head = (head < LAST_USER_CONTEXT-1) ? head+1 : 0;
 	mmu_context_queue.head = head;
@@ -132,8 +130,7 @@ destroy_context(struct mm_struct *mm)
 #endif
 
 	mmu_context_queue.size++;
-	mmu_context_queue.elements[index] =
-		mm->context & ~CONTEXT_LOW_HPAGES;
+	mmu_context_queue.elements[index] = mm->context.id;
 
 	spin_unlock_irqrestore(&mmu_context_queue.lock, flags);
 }
@@ -212,8 +209,6 @@ get_vsid( unsigned long context, unsigned long ea )
 {
 	unsigned long ordinal, vsid;
 
-	context &= ~CONTEXT_LOW_HPAGES;
-
 	ordinal = (((ea >> 28) & 0x1fffff) * LAST_USER_CONTEXT) | context;
 	vsid = (ordinal * VSID_RANDOMIZER) & VSID_MASK;
 
diff --git a/include/asm-ppc64/page.h b/include/asm-ppc64/page.h
index 66b24246f50b..dd2c424fbef9 100644
--- a/include/asm-ppc64/page.h
+++ b/include/asm-ppc64/page.h
@@ -32,6 +32,7 @@
 /* For 64-bit processes the hugepage range is 1T-1.5T */
 #define TASK_HPAGE_BASE 	(0x0000010000000000UL)
 #define TASK_HPAGE_END 	(0x0000018000000000UL)
+
 /* For 32-bit processes the hugepage range is 2-3G */
 #define TASK_HPAGE_BASE_32	(0x80000000UL)
 #define TASK_HPAGE_END_32	(0xc0000000UL)
@@ -39,7 +40,7 @@
 #define ARCH_HAS_HUGEPAGE_ONLY_RANGE
 #define is_hugepage_only_range(addr, len) \
 	( ((addr > (TASK_HPAGE_BASE-len)) && (addr < TASK_HPAGE_END)) || \
-	  ((current->mm->context & CONTEXT_LOW_HPAGES) && \
+	  (current->mm->context.low_hpages && \
 	   (addr > (TASK_HPAGE_BASE_32-len)) && (addr < TASK_HPAGE_END_32)) )
 #define hugetlb_free_pgtables free_pgtables
 #define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
@@ -47,7 +48,7 @@
 #define in_hugepage_area(context, addr) \
 	((cur_cpu_spec->cpu_features & CPU_FTR_16M_PAGE) && \
 	 ((((addr) >= TASK_HPAGE_BASE) && ((addr) < TASK_HPAGE_END)) || \
-	  (((context) & CONTEXT_LOW_HPAGES) && \
+	  ((context).low_hpages && \
 	   (((addr) >= TASK_HPAGE_BASE_32) && ((addr) < TASK_HPAGE_END_32)))))
 
 #else /* !CONFIG_HUGETLB_PAGE */