#define __PPC64_MMU_CONTEXT_H
#include <linux/config.h>
-#include <linux/spinlock.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <asm/mmu.h>
-#include <asm/ppcdebug.h>
#include <asm/cputable.h>
/*
return __ffs(b[2]) + 128;
}
-#define NO_CONTEXT 0
-#define FIRST_USER_CONTEXT 0x10 /* First 16 reserved for kernel */
-#define LAST_USER_CONTEXT 0x8000 /* Same as PID_MAX for now... */
-#define NUM_USER_CONTEXT (LAST_USER_CONTEXT-FIRST_USER_CONTEXT)
-
-/* Choose whether we want to implement our context
- * number allocator as a LIFO or FIFO queue.
- */
-#if 1
-#define MMU_CONTEXT_LIFO
-#else
-#define MMU_CONTEXT_FIFO
-#endif
-
-struct mmu_context_queue_t {
- spinlock_t lock;
- long head;
- long tail;
- long size;
- mm_context_id_t elements[LAST_USER_CONTEXT];
-};
-
-extern struct mmu_context_queue_t mmu_context_queue;
-
-static inline void
-enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
-{
-}
-
-/*
- * The context number queue has underflowed.
- * Meaning: we tried to push a context number that was freed
- * back onto the context queue and the queue was already full.
- */
-static inline void
-mmu_context_underflow(void)
-{
- printk(KERN_DEBUG "mmu_context_underflow\n");
- panic("mmu_context_underflow");
-}
-
-/*
- * Set up the context for a new address space.
- */
-static inline int
-init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
- long head;
- unsigned long flags;
- /* This does the right thing across a fork (I hope) */
-
- spin_lock_irqsave(&mmu_context_queue.lock, flags);
-
- if (mmu_context_queue.size <= 0) {
- spin_unlock_irqrestore(&mmu_context_queue.lock, flags);
- return -ENOMEM;
- }
-
- head = mmu_context_queue.head;
- mm->context.id = mmu_context_queue.elements[head];
-
- head = (head < LAST_USER_CONTEXT-1) ? head+1 : 0;
- mmu_context_queue.head = head;
- mmu_context_queue.size--;
-
- spin_unlock_irqrestore(&mmu_context_queue.lock, flags);
-
- return 0;
}
-/*
- * We're finished using the context for an address space.
- */
-static inline void
-destroy_context(struct mm_struct *mm)
-{
- long index;
- unsigned long flags;
-
- spin_lock_irqsave(&mmu_context_queue.lock, flags);
+#define NO_CONTEXT 0
+#define MAX_CONTEXT (0x100000-1)
- if (mmu_context_queue.size >= NUM_USER_CONTEXT) {
- spin_unlock_irqrestore(&mmu_context_queue.lock, flags);
- mmu_context_underflow();
- }
+extern int init_new_context(struct task_struct *tsk, struct mm_struct *mm);
+extern void destroy_context(struct mm_struct *mm);
-#ifdef MMU_CONTEXT_LIFO
- index = mmu_context_queue.head;
- index = (index > 0) ? index-1 : LAST_USER_CONTEXT-1;
- mmu_context_queue.head = index;
-#else
- index = mmu_context_queue.tail;
- index = (index < LAST_USER_CONTEXT-1) ? index+1 : 0;
- mmu_context_queue.tail = index;
-#endif
-
- mmu_context_queue.size++;
- mmu_context_queue.elements[index] = mm->context.id;
-
- spin_unlock_irqrestore(&mmu_context_queue.lock, flags);
-}
-
-extern void flush_stab(struct task_struct *tsk, struct mm_struct *mm);
+extern void switch_stab(struct task_struct *tsk, struct mm_struct *mm);
extern void switch_slb(struct task_struct *tsk, struct mm_struct *mm);
/*
if (cur_cpu_spec->cpu_features & CPU_FTR_SLB)
switch_slb(tsk, next);
else
- flush_stab(tsk, next);
+ switch_stab(tsk, next);
}
#define deactivate_mm(tsk,mm) do { } while (0)
local_irq_restore(flags);
}
-/* This is only valid for kernel (including vmalloc, imalloc and bolted) EA's
+/* VSID allocation
+ * ===============
+ *
+ * We first generate a 36-bit "proto-VSID". For kernel addresses this
+ * is equal to the ESID, for user addresses it is:
+ * (context << 15) | (esid & 0x7fff)
+ *
+ * The two forms are distinguishable because the top bit is 0 for user
+ * addresses, whereas the top two bits are 1 for kernel addresses.
+ * Proto-VSIDs with the top two bits equal to 0b10 are reserved for
+ * now.
+ *
+ * The proto-VSIDs are then scrambled into real VSIDs with the
+ * multiplicative hash:
+ *
+ * VSID = (proto-VSID * VSID_MULTIPLIER) % VSID_MODULUS
+ * where VSID_MULTIPLIER = 268435399 = 0xFFFFFC7
+ * VSID_MODULUS = 2^36-1 = 0xFFFFFFFFF
+ *
+ * This scramble is only well defined for proto-VSIDs below
+ * 0xFFFFFFFFF, so both proto-VSID and actual VSID 0xFFFFFFFFF are
+ * reserved. VSID_MULTIPLIER is prime, so in particular it is
+ * co-prime to VSID_MODULUS, making this a 1:1 scrambling function.
+ * Because the modulus is 2^n-1 we can compute it efficiently without
+ * a divide or extra multiply (see below).
+ *
+ * This scheme has several advantages over older methods:
+ *
+ * - We have VSIDs allocated for every kernel address
+ * (i.e. everything above 0xC000000000000000), except the very top
+ * segment, which simplifies several things.
+ *
+ * - We allow for 15 significant bits of ESID and 20 bits of
+ * context for user addresses. i.e. 8T (43 bits) of address space for
+ * up to 1M contexts (although the page table structure and context
+ * allocation will need changes to take advantage of this).
+ *
+ * - The scramble function gives robust scattering in the hash
+ * table (at least based on some initial results). The previous
+ * method was more susceptible to pathological cases giving excessive
+ * hash collisions.
*/
-static inline unsigned long
-get_kernel_vsid( unsigned long ea )
-{
- unsigned long ordinal, vsid;
-
- ordinal = (((ea >> 28) & 0x1fff) * LAST_USER_CONTEXT) | (ea >> 60);
- vsid = (ordinal * VSID_RANDOMIZER) & VSID_MASK;
-
-#ifdef HTABSTRESS
- /* For debug, this path creates a very poor vsid distribuition.
- * A user program can access virtual addresses in the form
- * 0x0yyyyxxxx000 where yyyy = xxxx to cause multiple mappings
- * to hash to the same page table group.
- */
- ordinal = ((ea >> 28) & 0x1fff) | (ea >> 44);
- vsid = ordinal & VSID_MASK;
-#endif /* HTABSTRESS */
-
- return vsid;
-}
-
-/* This is only valid for user EA's (user EA's do not exceed 2^41 (EADDR_SIZE))
+
+/*
+ * WARNING - If you change these you must make sure the asm
+ * implementations in slb_allocate(), do_stab_bolted and mmu.h
+ * (ASM_VSID_SCRAMBLE macro) are changed accordingly.
+ *
+ * You'll also need to change the precomputed VSID values in head.S
+ * which are used by the iSeries firmware.
*/
-static inline unsigned long
-get_vsid( unsigned long context, unsigned long ea )
-{
- unsigned long ordinal, vsid;
- ordinal = (((ea >> 28) & 0x1fff) * LAST_USER_CONTEXT) | context;
- vsid = (ordinal * VSID_RANDOMIZER) & VSID_MASK;
+static inline unsigned long vsid_scramble(unsigned long protovsid)
+{
+#if 0
+ /* The code below is equivalent to this function for arguments
+ * < 2^VSID_BITS, which is all this should ever be called
+ * with. However gcc is not clever enough to compute the
+ * modulus (2^n-1) without a second multiply. */
+ return ((protovsid * VSID_MULTIPLIER) % VSID_MODULUS);
+#else /* 1 */
+ unsigned long x;
+
+ x = protovsid * VSID_MULTIPLIER;
+ x = (x >> VSID_BITS) + (x & VSID_MODULUS);
+ return (x + ((x+1) >> VSID_BITS)) & VSID_MODULUS;
+#endif /* 1 */
+}
-#ifdef HTABSTRESS
- /* See comment above. */
- ordinal = ((ea >> 28) & 0x1fff) | (context << 16);
- vsid = ordinal & VSID_MASK;
-#endif /* HTABSTRESS */
+/* This is only valid for addresses >= KERNELBASE */
+static inline unsigned long get_kernel_vsid(unsigned long ea)
+{
+ return vsid_scramble(ea >> SID_SHIFT);
+}
- return vsid;
+/* This is only valid for user addresses (which are below 2^41) */
+static inline unsigned long get_vsid(unsigned long context, unsigned long ea)
+{
+ return vsid_scramble((context << USER_ESID_BITS)
+ | (ea >> SID_SHIFT));
}
#endif /* __PPC64_MMU_CONTEXT_H */
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