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