132 lines
4.4 KiB
C
132 lines
4.4 KiB
C
/*
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* Copyright 2010 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*/
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#ifndef _ASM_TILE_MMU_CONTEXT_H
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#define _ASM_TILE_MMU_CONTEXT_H
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#include <linux/smp.h>
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#include <asm/setup.h>
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#include <asm/page.h>
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#include <asm/pgalloc.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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#include <asm/homecache.h>
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#include <asm-generic/mm_hooks.h>
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static inline int
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init_new_context(struct task_struct *tsk, struct mm_struct *mm)
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{
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return 0;
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}
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/* Note that arch/tile/kernel/head.S also calls hv_install_context() */
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static inline void __install_page_table(pgd_t *pgdir, int asid, pgprot_t prot)
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{
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/* FIXME: DIRECTIO should not always be set. FIXME. */
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int rc = hv_install_context(__pa(pgdir), prot, asid, HV_CTX_DIRECTIO);
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if (rc < 0)
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panic("hv_install_context failed: %d", rc);
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}
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static inline void install_page_table(pgd_t *pgdir, int asid)
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{
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pte_t *ptep = virt_to_pte(NULL, (unsigned long)pgdir);
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__install_page_table(pgdir, asid, *ptep);
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}
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/*
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* "Lazy" TLB mode is entered when we are switching to a kernel task,
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* which borrows the mm of the previous task. The goal of this
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* optimization is to avoid having to install a new page table. On
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* early x86 machines (where the concept originated) you couldn't do
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* anything short of a full page table install for invalidation, so
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* handling a remote TLB invalidate required doing a page table
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* re-install. Someone clearly decided that it was silly to keep
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* doing this while in "lazy" TLB mode, so the optimization involves
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* installing the swapper page table instead the first time one
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* occurs, and clearing the cpu out of cpu_vm_mask, so the cpu running
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* the kernel task doesn't need to take any more interrupts. At that
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* point it's then necessary to explicitly reinstall it when context
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* switching back to the original mm.
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*
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* On Tile, we have to do a page-table install whenever DMA is enabled,
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* so in that case lazy mode doesn't help anyway. And more generally,
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* we have efficient per-page TLB shootdown, and don't expect to spend
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* that much time in kernel tasks in general, so just leaving the
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* kernel task borrowing the old page table, but handling TLB
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* shootdowns, is a reasonable thing to do. And importantly, this
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* lets us use the hypervisor's internal APIs for TLB shootdown, which
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* means we don't have to worry about having TLB shootdowns blocked
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* when Linux is disabling interrupts; see the page migration code for
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* an example of where it's important for TLB shootdowns to complete
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* even when interrupts are disabled at the Linux level.
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*/
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static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *t)
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{
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#if CHIP_HAS_TILE_DMA()
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/*
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* We have to do an "identity" page table switch in order to
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* clear any pending DMA interrupts.
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*/
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if (current->thread.tile_dma_state.enabled)
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install_page_table(mm->pgd, __get_cpu_var(current_asid));
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#endif
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}
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static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *tsk)
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{
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if (likely(prev != next)) {
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int cpu = smp_processor_id();
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/* Pick new ASID. */
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int asid = __get_cpu_var(current_asid) + 1;
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if (asid > max_asid) {
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asid = min_asid;
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local_flush_tlb();
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}
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__get_cpu_var(current_asid) = asid;
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/* Clear cpu from the old mm, and set it in the new one. */
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cpumask_clear_cpu(cpu, mm_cpumask(prev));
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cpumask_set_cpu(cpu, mm_cpumask(next));
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/* Re-load page tables */
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install_page_table(next->pgd, asid);
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/* See how we should set the red/black cache info */
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check_mm_caching(prev, next);
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/*
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* Since we're changing to a new mm, we have to flush
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* the icache in case some physical page now being mapped
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* has subsequently been repurposed and has new code.
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*/
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__flush_icache();
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}
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}
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static inline void activate_mm(struct mm_struct *prev_mm,
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struct mm_struct *next_mm)
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{
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switch_mm(prev_mm, next_mm, NULL);
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}
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#define destroy_context(mm) do { } while (0)
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#define deactivate_mm(tsk, mm) do { } while (0)
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#endif /* _ASM_TILE_MMU_CONTEXT_H */
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