arch/riscv/include/asm/mmu_context.h

   1 /*
   2  * Copyright (C) 2012 Regents of the University of California
   3  * Copyright (C) 2017 SiFive
   4  *
   5  *   This program is free software; you can redistribute it and/or
   6  *   modify it under the terms of the GNU General Public License
   7  *   as published by the Free Software Foundation, version 2.
   8  *
   9  *   This program is distributed in the hope that it will be useful,
  10  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *   GNU General Public License for more details.
  13  */
  14
  15 #ifndef _ASM_RISCV_MMU_CONTEXT_H
  16 #define _ASM_RISCV_MMU_CONTEXT_H
  17
  18 #include <linux/mm_types.h>
  19 #include <asm-generic/mm_hooks.h>
  20
  21 #include <linux/mm.h>
  22 #include <linux/sched.h>
  23 #include <asm/tlbflush.h>
  24 #include <asm/cacheflush.h>
  25
  26 static inline void enter_lazy_tlb(struct mm_struct *mm,
  27         struct task_struct *task)
  28 {
  29 }
  30
  31 /* Initialize context-related info for a new mm_struct */
  32 static inline int init_new_context(struct task_struct *task,
  33         struct mm_struct *mm)
  34 {
  35         return 0;
  36 }
  37
  38 static inline void destroy_context(struct mm_struct *mm)
  39 {
  40 }
  41
  42 static inline pgd_t *current_pgdir(void)
  43 {
  44         return pfn_to_virt(csr_read(sptbr) & SPTBR_PPN);
  45 }
  46
  47 static inline void set_pgdir(pgd_t *pgd)
  48 {
  49         csr_write(sptbr, virt_to_pfn(pgd) | SPTBR_MODE);
  50 }
  51
  52 /*
  53  * When necessary, performs a deferred icache flush for the given MM context,
  54  * on the local CPU.  RISC-V has no direct mechanism for instruction cache
  55  * shoot downs, so instead we send an IPI that informs the remote harts they
  56  * need to flush their local instruction caches.  To avoid pathologically slow
  57  * behavior in a common case (a bunch of single-hart processes on a many-hart
  58  * machine, ie 'make -j') we avoid the IPIs for harts that are not currently
  59  * executing a MM context and instead schedule a deferred local instruction
  60  * cache flush to be performed before execution resumes on each hart.  This
  61  * actually performs that local instruction cache flush, which implicitly only
  62  * refers to the current hart.
  63  */
  64 static inline void flush_icache_deferred(struct mm_struct *mm)
  65 {
  66 #ifdef CONFIG_SMP
  67         unsigned int cpu = smp_processor_id();
  68         cpumask_t *mask = &mm->context.icache_stale_mask;
  69
  70         if (cpumask_test_cpu(cpu, mask)) {
  71                 cpumask_clear_cpu(cpu, mask);
  72                 /*
  73                  * Ensure the remote hart's writes are visible to this hart.
  74                  * This pairs with a barrier in flush_icache_mm.
  75                  */
  76                 smp_mb();
  77                 local_flush_icache_all();
  78         }
  79 #endif
  80 }
  81
  82 static inline void switch_mm(struct mm_struct *prev,
  83         struct mm_struct *next, struct task_struct *task)
  84 {
  85         if (likely(prev != next)) {
  86                 /*
  87                  * Mark the current MM context as inactive, and the next as
  88                  * active.  This is at least used by the icache flushing
  89                  * routines in order to determine who should
  90                  */
  91                 unsigned int cpu = smp_processor_id();
  92
  93                 cpumask_clear_cpu(cpu, mm_cpumask(prev));
  94                 cpumask_set_cpu(cpu, mm_cpumask(next));
  95
  96                 set_pgdir(next->pgd);
  97                 local_flush_tlb_all();
  98
  99                 flush_icache_deferred(next);
 100         }
 101 }
 102
 103 static inline void activate_mm(struct mm_struct *prev,
 104                                struct mm_struct *next)
 105 {
 106         switch_mm(prev, next, NULL);
 107 }
 108
 109 static inline void deactivate_mm(struct task_struct *task,
 110         struct mm_struct *mm)
 111 {
 112 }
 113
 114 #endif /* _ASM_RISCV_MMU_CONTEXT_H */