Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 197 insertions, 0 deletions

diff --git a/include/asm-ppc/mmu_context.h b/include/asm-ppc/mmu_context.h
new file mode 100644
index 000000000000..9222fa6ca172
--- /dev/null
+++ b/include/asm-ppc/mmu_context.h
@@ -0,0 +1,197 @@
+#ifdef __KERNEL__
+#ifndef __PPC_MMU_CONTEXT_H
+#define __PPC_MMU_CONTEXT_H
+
+#include <linux/config.h>
+#include <asm/atomic.h>
+#include <asm/bitops.h>
+#include <asm/mmu.h>
+#include <asm/cputable.h>
+
+/*
+ * On 32-bit PowerPC 6xx/7xx/7xxx CPUs, we use a set of 16 VSIDs
+ * (virtual segment identifiers) for each context.  Although the
+ * hardware supports 24-bit VSIDs, and thus >1 million contexts,
+ * we only use 32,768 of them.  That is ample, since there can be
+ * at most around 30,000 tasks in the system anyway, and it means
+ * that we can use a bitmap to indicate which contexts are in use.
+ * Using a bitmap means that we entirely avoid all of the problems
+ * that we used to have when the context number overflowed,
+ * particularly on SMP systems.
+ *  -- paulus.
+ */
+
+/*
+ * This function defines the mapping from contexts to VSIDs (virtual
+ * segment IDs).  We use a skew on both the context and the high 4 bits
+ * of the 32-bit virtual address (the "effective segment ID") in order
+ * to spread out the entries in the MMU hash table.  Note, if this
+ * function is changed then arch/ppc/mm/hashtable.S will have to be
+ * changed to correspond.
+ */
+#define CTX_TO_VSID(ctx, va)	(((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
+				 & 0xffffff)
+
+/*
+   The MPC8xx has only 16 contexts.  We rotate through them on each
+   task switch.  A better way would be to keep track of tasks that
+   own contexts, and implement an LRU usage.  That way very active
+   tasks don't always have to pay the TLB reload overhead.  The
+   kernel pages are mapped shared, so the kernel can run on behalf
+   of any task that makes a kernel entry.  Shared does not mean they
+   are not protected, just that the ASID comparison is not performed.
+        -- Dan
+
+   The IBM4xx has 256 contexts, so we can just rotate through these
+   as a way of "switching" contexts.  If the TID of the TLB is zero,
+   the PID/TID comparison is disabled, so we can use a TID of zero
+   to represent all kernel pages as shared among all contexts.
+   	-- Dan
+ */
+
+static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+}
+
+#ifdef CONFIG_8xx
+#define NO_CONTEXT      	16
+#define LAST_CONTEXT    	15
+#define FIRST_CONTEXT    	0
+
+#elif defined(CONFIG_4xx)
+#define NO_CONTEXT      	256
+#define LAST_CONTEXT    	255
+#define FIRST_CONTEXT    	1
+
+#elif defined(CONFIG_E500)
+#define NO_CONTEXT      	256
+#define LAST_CONTEXT    	255
+#define FIRST_CONTEXT    	1
+
+#else
+
+/* PPC 6xx, 7xx CPUs */
+#define NO_CONTEXT      	((mm_context_t) -1)
+#define LAST_CONTEXT    	32767
+#define FIRST_CONTEXT    	1
+#endif
+
+/*
+ * Set the current MMU context.
+ * On 32-bit PowerPCs (other than the 8xx embedded chips), this is done by
+ * loading up the segment registers for the user part of the address space.
+ *
+ * Since the PGD is immediately available, it is much faster to simply
+ * pass this along as a second parameter, which is required for 8xx and
+ * can be used for debugging on all processors (if you happen to have
+ * an Abatron).
+ */
+extern void set_context(mm_context_t context, pgd_t *pgd);
+
+/*
+ * Bitmap of contexts in use.
+ * The size of this bitmap is LAST_CONTEXT + 1 bits.
+ */
+extern unsigned long context_map[];
+
+/*
+ * This caches the next context number that we expect to be free.
+ * Its use is an optimization only, we can't rely on this context
+ * number to be free, but it usually will be.
+ */
+extern mm_context_t next_mmu_context;
+
+/*
+ * If we don't have sufficient contexts to give one to every task
+ * that could be in the system, we need to be able to steal contexts.
+ * These variables support that.
+ */
+#if LAST_CONTEXT < 30000
+#define FEW_CONTEXTS	1
+extern atomic_t nr_free_contexts;
+extern struct mm_struct *context_mm[LAST_CONTEXT+1];
+extern void steal_context(void);
+#endif
+
+/*
+ * Get a new mmu context for the address space described by `mm'.
+ */
+static inline void get_mmu_context(struct mm_struct *mm)
+{
+	mm_context_t ctx;
+
+	if (mm->context != NO_CONTEXT)
+		return;
+#ifdef FEW_CONTEXTS
+	while (atomic_dec_if_positive(&nr_free_contexts) < 0)
+		steal_context();
+#endif
+	ctx = next_mmu_context;
+	while (test_and_set_bit(ctx, context_map)) {
+		ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
+		if (ctx > LAST_CONTEXT)
+			ctx = 0;
+	}
+	next_mmu_context = (ctx + 1) & LAST_CONTEXT;
+	mm->context = ctx;
+#ifdef FEW_CONTEXTS
+	context_mm[ctx] = mm;
+#endif
+}
+
+/*
+ * Set up the context for a new address space.
+ */
+#define init_new_context(tsk,mm)	(((mm)->context = NO_CONTEXT), 0)
+
+/*
+ * We're finished using the context for an address space.
+ */
+static inline void destroy_context(struct mm_struct *mm)
+{
+	if (mm->context != NO_CONTEXT) {
+		clear_bit(mm->context, context_map);
+		mm->context = NO_CONTEXT;
+#ifdef FEW_CONTEXTS
+		atomic_inc(&nr_free_contexts);
+#endif
+	}
+}
+
+static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+			     struct task_struct *tsk)
+{
+#ifdef CONFIG_ALTIVEC
+	asm volatile (
+ BEGIN_FTR_SECTION
+	"dssall;\n"
+#ifndef CONFIG_POWER4
+	 "sync;\n" /* G4 needs a sync here, G5 apparently not */
+#endif
+ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
+	 : : );
+#endif /* CONFIG_ALTIVEC */
+
+	tsk->thread.pgdir = next->pgd;
+
+	/* No need to flush userspace segments if the mm doesnt change */
+	if (prev == next)
+		return;
+
+	/* Setup new userspace context */
+	get_mmu_context(next);
+	set_context(next->context, next->pgd);
+}
+
+#define deactivate_mm(tsk,mm)	do { } while (0)
+
+/*
+ * After we have set current->mm to a new value, this activates
+ * the context for the new mm so we see the new mappings.
+ */
+#define activate_mm(active_mm, mm)   switch_mm(active_mm, mm, current)
+
+extern void mmu_context_init(void);
+
+#endif /* __PPC_MMU_CONTEXT_H */
+#endif /* __KERNEL__ */