arch/arm64/include/asm/mmu_context.h

   1 /*
   2  * Based on arch/arm/include/asm/mmu_context.h
   3  *
   4  * Copyright (C) 1996 Russell King.
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19 #ifndef __ASM_MMU_CONTEXT_H
  20 #define __ASM_MMU_CONTEXT_H
  21
  22 #include <linux/compiler.h>
  23 #include <linux/sched.h>
  24
  25 #include <asm/cacheflush.h>
  26 #include <asm/proc-fns.h>
  27 #include <asm-generic/mm_hooks.h>
  28 #include <asm/cputype.h>
  29 #include <asm/pgtable.h>
  30
  31 #define MAX_ASID_BITS   16
  32
  33 extern unsigned int cpu_last_asid;
  34
  35 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
  36 void __new_context(struct mm_struct *mm);
  37
  38 #ifdef CONFIG_PID_IN_CONTEXTIDR
  39 static inline void contextidr_thread_switch(struct task_struct *next)
  40 {
  41         asm(
  42         "       msr     contextidr_el1, %0\n"
  43         "       isb"
  44         :
  45         : "r" (task_pid_nr(next)));
  46 }
  47 #else
  48 static inline void contextidr_thread_switch(struct task_struct *next)
  49 {
  50 }
  51 #endif
  52
  53 /*
  54  * Set TTBR0 to empty_zero_page. No translations will be possible via TTBR0.
  55  */
  56 static inline void cpu_set_reserved_ttbr0(void)
  57 {
  58         unsigned long ttbr = page_to_phys(empty_zero_page);
  59
  60         asm(
  61         "       msr     ttbr0_el1, %0                   // set TTBR0\n"
  62         "       isb"
  63         :
  64         : "r" (ttbr));
  65 }
  66
  67 /*
  68  * TCR.T0SZ value to use when the ID map is active. Usually equals
  69  * TCR_T0SZ(VA_BITS), unless system RAM is positioned very high in
  70  * physical memory, in which case it will be smaller.
  71  */
  72 extern u64 idmap_t0sz;
  73
  74 static inline bool __cpu_uses_extended_idmap(void)
  75 {
  76         return (!IS_ENABLED(CONFIG_ARM64_VA_BITS_48) &&
  77                 unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS)));
  78 }
  79
  80 /*
  81  * Set TCR.T0SZ to its default value (based on VA_BITS)
  82  */
  83 static inline void cpu_set_default_tcr_t0sz(void)
  84 {
  85         unsigned long tcr;
  86
  87         if (!__cpu_uses_extended_idmap())
  88                 return;
  89
  90         asm volatile (
  91         "       mrs     %0, tcr_el1     ;"
  92         "       bfi     %0, %1, %2, %3  ;"
  93         "       msr     tcr_el1, %0     ;"
  94         "       isb"
  95         : "=&r" (tcr)
  96         : "r"(TCR_T0SZ(VA_BITS)), "I"(TCR_T0SZ_OFFSET), "I"(TCR_TxSZ_WIDTH));
  97 }
  98
  99 static inline void switch_new_context(struct mm_struct *mm)
 100 {
 101         unsigned long flags;
 102
 103         __new_context(mm);
 104
 105         local_irq_save(flags);
 106         cpu_switch_mm(mm->pgd, mm);
 107         local_irq_restore(flags);
 108 }
 109
 110 static inline void check_and_switch_context(struct mm_struct *mm,
 111                                             struct task_struct *tsk)
 112 {
 113         /*
 114          * Required during context switch to avoid speculative page table
 115          * walking with the wrong TTBR.
 116          */
 117         cpu_set_reserved_ttbr0();
 118
 119         if (!((mm->context.id ^ cpu_last_asid) >> MAX_ASID_BITS))
 120                 /*
 121                  * The ASID is from the current generation, just switch to the
 122                  * new pgd. This condition is only true for calls from
 123                  * context_switch() and interrupts are already disabled.
 124                  */
 125                 cpu_switch_mm(mm->pgd, mm);
 126         else if (irqs_disabled())
 127                 /*
 128                  * Defer the new ASID allocation until after the context
 129                  * switch critical region since __new_context() cannot be
 130                  * called with interrupts disabled.
 131                  */
 132                 set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM);
 133         else
 134                 /*
 135                  * That is a direct call to switch_mm() or activate_mm() with
 136                  * interrupts enabled and a new context.
 137                  */
 138                 switch_new_context(mm);
 139 }
 140
 141 #define init_new_context(tsk,mm)        (__init_new_context(tsk,mm),0)
 142 #define destroy_context(mm)             do { } while(0)
 143
 144 #define finish_arch_post_lock_switch \
 145         finish_arch_post_lock_switch
 146 static inline void finish_arch_post_lock_switch(void)
 147 {
 148         if (test_and_clear_thread_flag(TIF_SWITCH_MM)) {
 149                 struct mm_struct *mm = current->mm;
 150                 unsigned long flags;
 151
 152                 __new_context(mm);
 153
 154                 local_irq_save(flags);
 155                 cpu_switch_mm(mm->pgd, mm);
 156                 local_irq_restore(flags);
 157         }
 158 }
 159
 160 /*
 161  * This is called when "tsk" is about to enter lazy TLB mode.
 162  *
 163  * mm:  describes the currently active mm context
 164  * tsk: task which is entering lazy tlb
 165  * cpu: cpu number which is entering lazy tlb
 166  *
 167  * tsk->mm will be NULL
 168  */
 169 static inline void
 170 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 171 {
 172 }
 173
 174 /*
 175  * This is the actual mm switch as far as the scheduler
 176  * is concerned.  No registers are touched.  We avoid
 177  * calling the CPU specific function when the mm hasn't
 178  * actually changed.
 179  */
 180 static inline void
 181 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 182           struct task_struct *tsk)
 183 {
 184         unsigned int cpu = smp_processor_id();
 185
 186         /*
 187          * init_mm.pgd does not contain any user mappings and it is always
 188          * active for kernel addresses in TTBR1. Just set the reserved TTBR0.
 189          */
 190         if (next == &init_mm) {
 191                 cpu_set_reserved_ttbr0();
 192                 return;
 193         }
 194
 195         if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next)
 196                 check_and_switch_context(next, tsk);
 197 }
 198
 199 #define deactivate_mm(tsk,mm)   do { } while (0)
 200 #define activate_mm(prev,next)  switch_mm(prev, next, NULL)
 201
 202 #endif