mmu_context.h

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#ifndef _ASM_IA64_MMU_CONTEXT_H
#define _ASM_IA64_MMU_CONTEXT_H

/*
 * Copyright (C) 1998-2000 Hewlett-Packard Co
 * Copyright (C) 1998-2000 David Mosberger-Tang <[e-mail]>
 */

#include <linux/sched.h>
#include <linux/spinlock.h>

#include <asm/processor.h>

/*
 * Routines to manage the allocation of task context numbers.  Task
 * context numbers are used to reduce or eliminate the need to perform
 * TLB flushes due to context switches.  Context numbers are
 * implemented using ia-64 region ids.  Since ia-64 TLBs do not
 * guarantee that the region number is checked when performing a TLB
 * lookup, we need to assign a unique region id to each region in a
 * process.  We use the least significant three bits in a region id
 * for this purpose.  On processors where the region number is checked
 * in TLB lookups, we can get back those two bits by defining
 * CONFIG_IA64_TLB_CHECKS_REGION_NUMBER.  The macro
 * IA64_REGION_ID_BITS gives the number of bits in a region id.  The
 * architecture manual guarantees this number to be in the range
 * 18-24.
 *
 * Copyright (C) 1998 David Mosberger-Tang <[e-mail]>
 */

#define IA64_REGION_ID_KERNEL	0 /* the kernel's region id (tlb.c depends on this being 0) */

struct ia64_ctx {
	spinlock_t lock;
	unsigned int next;	/* next context number to use */
	unsigned int limit;	/* next >= limit => must call wrap_mmu_context() */
	unsigned int max_ctx;	/* max. context value supported by all CPUs */
};

extern struct ia64_ctx ia64_ctx;

extern void wrap_mmu_context (struct mm_struct *mm);

static inline void
enter_lazy_tlb (struct mm_struct *mm, struct task_struct *tsk, unsigned cpu)
{
}

static inline unsigned long
ia64_rid (unsigned long context, unsigned long region_addr)
{
	return context << 3 | (region_addr >> 61);
}

static inline void
get_new_mmu_context (struct mm_struct *mm)
{
	spin_lock(&ia64_ctx.lock);
	{
		if (ia64_ctx.next >= ia64_ctx.limit)
			wrap_mmu_context(mm);
		mm->context = ia64_ctx.next++;
	}
	spin_unlock(&ia64_ctx.lock);

}

static inline void
get_mmu_context (struct mm_struct *mm)
{
	/* check if our ASN is of an older generation and thus invalid: */
	if (mm->context == 0)
		get_new_mmu_context(mm);
}

static inline int
init_new_context (struct task_struct *p, struct mm_struct *mm)
{
	mm->context = 0;
	return 0;
}

static inline void
destroy_context (struct mm_struct *mm)
{
	/* Nothing to do.  */
}

static inline void
reload_context (struct mm_struct *mm)
{
	unsigned long rid;
	unsigned long rid_incr = 0;
	unsigned long rr0, rr1, rr2, rr3, rr4;

	rid = mm->context << 3;	/* make space for encoding the region number */
	rid_incr = 1 << 8;

	/* encode the region id, preferred page size, and VHPT enable bit: */
	rr0 = (rid << 8) | (PAGE_SHIFT << 2) | 1;
	rr1 = rr0 + 1*rid_incr;
	rr2 = rr0 + 2*rid_incr;
	rr3 = rr0 + 3*rid_incr;
	rr4 = rr0 + 4*rid_incr;
	ia64_set_rr(0x0000000000000000, rr0);
	ia64_set_rr(0x2000000000000000, rr1);
	ia64_set_rr(0x4000000000000000, rr2);
	ia64_set_rr(0x6000000000000000, rr3);
	ia64_set_rr(0x8000000000000000, rr4);
	ia64_insn_group_barrier();
	ia64_srlz_i();			/* srlz.i implies srlz.d */
	ia64_insn_group_barrier();
}

/*
 * Switch from address space PREV to address space NEXT.
 */
static inline void
activate_mm (struct mm_struct *prev, struct mm_struct *next)
{
	/*
	 * We may get interrupts here, but that's OK because interrupt
	 * handlers cannot touch user-space.
	 */
	__asm__ __volatile__ ("mov ar.k7=%0" :: "r"(__pa(next->pgd)));
	get_mmu_context(next);
	reload_context(next);
}

#define switch_mm(prev_mm,next_mm,next_task,cpu)	activate_mm(prev_mm, next_mm)

#endif /* _ASM_IA64_MMU_CONTEXT_H */