| /* |
| * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| * vineetg: May 2011 |
| * -Refactored get_new_mmu_context( ) to only handle live-mm. |
| * retiring-mm handled in other hooks |
| * |
| * vineetg: April 2011 |
| * -CONFIG_ARC_MMU_SASID: support for ARC MMU Shared Address spaces |
| * activate_mm() and switch_mm() to setup MMU SASID reg with task's |
| * current sasid subscriptions |
| * |
| * Vineetg: March 25th, 2008: Bug #92690 |
| * -Major rewrite of Core ASID allocation routine get_new_mmu_context |
| * |
| * Amit Bhor, Sameer Dhavale: Codito Technologies 2004 |
| */ |
| |
| #ifndef _ASM_ARC_MMU_CONTEXT_H |
| #define _ASM_ARC_MMU_CONTEXT_H |
| |
| #include <asm/arcregs.h> |
| #include <asm/tlb.h> |
| |
| #ifndef CONFIG_MMAP_CODE_CMN_VADDR |
| #include <asm-generic/mm_hooks.h> |
| #else |
| extern void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm); |
| extern void arch_exit_mmap(struct mm_struct *mm); |
| #endif |
| |
| |
| #define FIRST_ASID 0 |
| #define MAX_ASID 255 /* ARC 700 8 bit PID field in PID Aux reg */ |
| #define NUM_ASID ((MAX_ASID - FIRST_ASID) + 1 ) |
| /* We use this to indicate that no ASID has been allocated to a mmu context */ |
| #define NO_ASID (MAX_ASID + 1) |
| |
| /* ASID to mm struct mapping */ |
| extern struct mm_struct *asid_mm_map[ NUM_ASID + 1 ]; |
| |
| extern int asid_cache; |
| |
| /* Get a new mmu context or a hardware PID/ASID to work with. |
| * If PID rolls over flush cache and tlb. |
| */ |
| static inline void |
| get_new_mmu_context(struct mm_struct *mm) |
| { |
| struct mm_struct *prev_owner; |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| |
| /* Relinquish the currently owned ASID (if any). |
| * Doing unconditionally saves a cmp-n-branch; |
| * for invalid asid, the array index is still valid |
| */ |
| asid_mm_map[mm->context.asid] = (struct mm_struct *) NULL; |
| |
| /* move to new asid */ |
| if ( ++asid_cache > MAX_ASID) { /* asid roll-over */ |
| asid_cache = FIRST_ASID; |
| flush_tlb_all(); |
| } |
| |
| /* Is new ASID already owned by some-one else (we are stealing it). |
| * If yes, let the orig owner be aware of this fact, so that when it runs, |
| * it asks for a brand new ASID. This would only happen for a long-lived |
| * task with asid from prev allocation cycle (before asid roll-over). |
| * |
| * This might look wrong - if we are re-using some other task's ASID, |
| * won't we use it's stale TLB entries too. Actually switch_mm( ) takes |
| * care of such a case: it ensures that a task with asid from prev alloc |
| * cycle, when scheduled will refresh it's ASID - see switch_mm( ) below |
| * The scenario of stealing here will only happen if that task didn't get |
| * a chance to refresh it's asid. |
| */ |
| if ( (prev_owner = asid_mm_map[asid_cache]) ) { |
| prev_owner->context.asid = NO_ASID; |
| } |
| |
| /* Assign new ASID to tsk */ |
| asid_mm_map[asid_cache] = mm; |
| mm->context.asid = asid_cache; |
| |
| #ifdef CONFIG_ARC_TLB_DBG |
| printk ("ARC_TLB_DBG: NewMM=0x%x OldMM=0x%x task_struct=0x%x Task: %s," |
| " pid:%u, assigned asid:%lu\n", |
| (unsigned int)mm, (unsigned int)prev_owner, |
| (unsigned int)(mm->context.tsk), (mm->context.tsk)->comm, |
| (mm->context.tsk)->pid, mm->context.asid); |
| |
| /* This is to double check TLB entries already exist for |
| * this newly allocated ASID |
| */ |
| tlb_find_asid(asid_cache); |
| |
| #endif |
| |
| write_new_aux_reg(ARC_REG_PID, asid_cache|MMU_ENABLE); |
| |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Initialize the context related info for a new mm_struct |
| * instance. |
| */ |
| static inline int |
| init_new_context(struct task_struct *tsk, struct mm_struct *mm) |
| { |
| mm->context.asid = NO_ASID; |
| #ifdef CONFIG_ARC_TLB_DBG |
| mm->context.tsk = tsk; |
| #endif /* CONFIG_ARC_TLB_DBG */ |
| return 0; |
| } |
| |
| /* Switch the mm context */ |
| static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, |
| struct task_struct *tsk) |
| { |
| /* PGD cached in MMU reg to avoid 3 mem lookups: task->mm->pgd */ |
| write_new_aux_reg(ARC_REG_SCRATCH_DATA0, next->pgd); |
| |
| /* Allocate a new ASID if task doesn't have a valid one. |
| * This could happen if this task never had an asid (fresh after fork) or |
| * it's ASID was stolen - past an asid roll-over. Also in a special case, |
| * even if the ASID was valid, we allocate a new ASID, if this task is |
| * running for the first time afer an ASID rollover. |
| * This is part of simplistic asid allocation algorithm - which allows |
| * asid "stealing" - If asid-cache is at "x-1", a new req will allocate "x" |
| * evenif "x" is already allocated. The *IMP* thing is stolen asid's TLB |
| * entries are not flushed - which can cause stale TLB entry use. |
| * The problem case is: A long-lived task has asid "x", asid_cache rolls |
| * over from 255 to 0, and later this task gets scheduled - creating TLB |
| * entries with "x". A little later, while asid_cache is "x-1" a task |
| * needs a new ASID, and steals this "x" while TLB entries already exist. |
| * To avoid this, we don't allow a ASID allocated in prev cycle to be used |
| * past a roll-over. |
| * |
| * Both the non-alloc scenario and first-use-after-rollover can be |
| * detected using the single condition below - since NO_ASID = 256 |
| * while asid_cache is always a valid asid value (0-255). |
| */ |
| if (next->context.asid > asid_cache) { |
| get_new_mmu_context(next); |
| } else { |
| // XXX: This will never happen given the chks above |
| // BUG_ON(next->context.asid > MAX_ASID); |
| write_new_aux_reg(ARC_REG_PID, next->context.asid|MMU_ENABLE); |
| } |
| |
| #ifdef CONFIG_ARC_MMU_SASID |
| { |
| unsigned int tsk_sasids; |
| |
| if ((tsk_sasids = is_any_mmapcode_task_subscribed(next))) { |
| write_new_aux_reg(ARC_REG_SASID, tsk_sasids); |
| } |
| } |
| #endif |
| |
| } |
| |
| static inline void destroy_context(struct mm_struct *mm) |
| { |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| |
| asid_mm_map[mm->context.asid] = NULL; |
| mm->context.asid = NO_ASID; |
| |
| local_irq_restore(flags); |
| } |
| |
| /* it seemed that deactivate_mm( ) is a reasonable place to do book-keeping |
| * for retiring-mm. However destroy_context( ) still needs to do that because |
| * between mm_release( ) = >deactive_mm( ) and |
| * mmput => .. => __mmdrop( ) => destroy_context( ) |
| * there is a good chance that task gets sched-out/in, making it's asid valid |
| * again (this teased me for a whole day). |
| */ |
| #define deactivate_mm(tsk,mm) do { } while (0) |
| |
| static inline void |
| activate_mm (struct mm_struct *prev, struct mm_struct *next) |
| { |
| write_new_aux_reg(ARC_REG_SCRATCH_DATA0, next->pgd); |
| |
| /* Unconditionally get a new ASID */ |
| get_new_mmu_context(next); |
| |
| #ifdef CONFIG_ARC_MMU_SASID |
| BUG_ON((is_any_mmapcode_task_subscribed(next))); |
| #endif |
| } |
| |
| #endif /* __ASM_ARC_MMU_CONTEXT_H */ |
