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#ifndef __ALPHA_MMU_CONTEXT_H
#define __ALPHA_MMU_CONTEXT_H
/*
* get a new mmu context..
*
* Copyright (C) 1996, Linus Torvalds
*/
#include <linux/config.h>
#include <asm/system.h>
/*
* The maximum ASN's the processor supports. On the EV4 this is 63
* but the PAL-code doesn't actually use this information. On the
* EV5 this is 127.
*
* On the EV4, the ASNs are more-or-less useless anyway, as they are
* only used as an icache tag, not for TB entries. On the EV5 ASN's
* also validate the TB entries, and thus make a lot more sense.
*
* The EV4 ASN's don't even match the architecture manual, ugh. And
* I quote: "If a processor implements address space numbers (ASNs),
* and the old PTE has the Address Space Match (ASM) bit clear (ASNs
* in use) and the Valid bit set, then entries can also effectively be
* made coherent by assigning a new, unused ASN to the currently
* running process and not reusing the previous ASN before calling the
* appropriate PALcode routine to invalidate the translation buffer
* (TB)".
*
* In short, the EV4 has a "kind of" ASN capability, but it doesn't actually
* work correctly and can thus not be used (explaining the lack of PAL-code
* support).
*/
#ifdef CONFIG_ALPHA_EV5
#define MAX_ASN 127
#else
#define MAX_ASN 63
#define BROKEN_ASN 1
#endif
extern unsigned long asn_cache;
#define ASN_VERSION_SHIFT 16
#define ASN_VERSION_MASK ((~0UL) << ASN_VERSION_SHIFT)
#define ASN_FIRST_VERSION (1UL << ASN_VERSION_SHIFT)
extern inline void get_new_mmu_context(struct task_struct *p,
struct mm_struct *mm,
unsigned long asn)
{
/* check if it's legal.. */
if ((asn & ~ASN_VERSION_MASK) > MAX_ASN) {
/* start a new version, invalidate all old asn's */
tbiap(); imb();
asn = (asn & ASN_VERSION_MASK) + ASN_FIRST_VERSION;
if (!asn)
asn = ASN_FIRST_VERSION;
}
asn_cache = asn + 1;
mm->context = asn; /* full version + asn */
p->tss.asn = asn & ~ASN_VERSION_MASK; /* just asn */
}
/*
* NOTE! The way this is set up, the high bits of the "asn_cache" (and
* the "mm->context") are the ASN _version_ code. A version of 0 is
* always considered invalid, so to invalidate another process you only
* need to do "p->mm->context = 0".
*
* If we need more ASN's than the processor has, we invalidate the old
* user TLB's (tbiap()) and start a new ASN version. That will automatically
* force a new asn for any other processes the next time they want to
* run.
*/
extern inline void get_mmu_context(struct task_struct *p)
{
#ifndef BROKEN_ASN
struct mm_struct * mm = p->mm;
if (mm) {
unsigned long asn = asn_cache;
/* Check if our ASN is of an older version and thus invalid */
if ((mm->context ^ asn) & ASN_VERSION_MASK)
get_new_mmu_context(p, mm, asn);
}
#endif
}
#define init_new_context(mm) do { } while(0)
#define destroy_context(mm) do { } while(0)
#endif
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