arch/alpha/include/asm/mmu_context.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __ALPHA_MMU_CONTEXT_H
   3 #define __ALPHA_MMU_CONTEXT_H
   4
   5 /*
   6  * get a new mmu context..
   7  *
   8  * Copyright (C) 1996, Linus Torvalds
   9  */
  10
  11 #include <linux/mm_types.h>
  12 #include <linux/sched.h>
  13
  14 #include <asm/machvec.h>
  15 #include <asm/compiler.h>
  16 #include <asm-generic/mm_hooks.h>
  17
  18 /*
  19  * Force a context reload. This is needed when we change the page
  20  * table pointer or when we update the ASN of the current process.
  21  */
  22
  23 /* Don't get into trouble with dueling __EXTERN_INLINEs.  */
  24 #ifndef __EXTERN_INLINE
  25 #include <asm/io.h>
  26 #endif
  27
  28
  29 static inline unsigned long
  30 __reload_thread(struct pcb_struct *pcb)
  31 {
  32         register unsigned long a0 __asm__("$16");
  33         register unsigned long v0 __asm__("$0");
  34
  35         a0 = virt_to_phys(pcb);
  36         __asm__ __volatile__(
  37                 "call_pal %2 #__reload_thread"
  38                 : "=r"(v0), "=r"(a0)
  39                 : "i"(PAL_swpctx), "r"(a0)
  40                 : "$1", "$22", "$23", "$24", "$25");
  41
  42         return v0;
  43 }
  44
  45
  46 /*
  47  * The maximum ASN's the processor supports.  On the EV4 this is 63
  48  * but the PAL-code doesn't actually use this information.  On the
  49  * EV5 this is 127, and EV6 has 255.
  50  *
  51  * On the EV4, the ASNs are more-or-less useless anyway, as they are
  52  * only used as an icache tag, not for TB entries.  On the EV5 and EV6,
  53  * ASN's also validate the TB entries, and thus make a lot more sense.
  54  *
  55  * The EV4 ASN's don't even match the architecture manual, ugh.  And
  56  * I quote: "If a processor implements address space numbers (ASNs),
  57  * and the old PTE has the Address Space Match (ASM) bit clear (ASNs
  58  * in use) and the Valid bit set, then entries can also effectively be
  59  * made coherent by assigning a new, unused ASN to the currently
  60  * running process and not reusing the previous ASN before calling the
  61  * appropriate PALcode routine to invalidate the translation buffer (TB)".
  62  *
  63  * In short, the EV4 has a "kind of" ASN capability, but it doesn't actually
  64  * work correctly and can thus not be used (explaining the lack of PAL-code
  65  * support).
  66  */
  67 #define EV4_MAX_ASN 63
  68 #define EV5_MAX_ASN 127
  69 #define EV6_MAX_ASN 255
  70
  71 #ifdef CONFIG_ALPHA_GENERIC
  72 # define MAX_ASN        (alpha_mv.max_asn)
  73 #else
  74 # ifdef CONFIG_ALPHA_EV4
  75 #  define MAX_ASN       EV4_MAX_ASN
  76 # elif defined(CONFIG_ALPHA_EV5)
  77 #  define MAX_ASN       EV5_MAX_ASN
  78 # else
  79 #  define MAX_ASN       EV6_MAX_ASN
  80 # endif
  81 #endif
  82
  83 /*
  84  * cpu_last_asn(processor):
  85  * 63                                            0
  86  * +-------------+----------------+--------------+
  87  * | asn version | this processor | hardware asn |
  88  * +-------------+----------------+--------------+
  89  */
  90
  91 #include <asm/smp.h>
  92 #ifdef CONFIG_SMP
  93 #define cpu_last_asn(cpuid)     (cpu_data[cpuid].last_asn)
  94 #else
  95 extern unsigned long last_asn;
  96 #define cpu_last_asn(cpuid)     last_asn
  97 #endif /* CONFIG_SMP */
  98
  99 #define WIDTH_HARDWARE_ASN      8
 100 #define ASN_FIRST_VERSION (1UL << WIDTH_HARDWARE_ASN)
 101 #define HARDWARE_ASN_MASK ((1UL << WIDTH_HARDWARE_ASN) - 1)
 102
 103 /*
 104  * NOTE! The way this is set up, the high bits of the "asn_cache" (and
 105  * the "mm->context") are the ASN _version_ code. A version of 0 is
 106  * always considered invalid, so to invalidate another process you only
 107  * need to do "p->mm->context = 0".
 108  *
 109  * If we need more ASN's than the processor has, we invalidate the old
 110  * user TLB's (tbiap()) and start a new ASN version. That will automatically
 111  * force a new asn for any other processes the next time they want to
 112  * run.
 113  */
 114
 115 #ifndef __EXTERN_INLINE
 116 #define __EXTERN_INLINE extern inline
 117 #define __MMU_EXTERN_INLINE
 118 #endif
 119
 120 extern inline unsigned long
 121 __get_new_mm_context(struct mm_struct *mm, long cpu)
 122 {
 123         unsigned long asn = cpu_last_asn(cpu);
 124         unsigned long next = asn + 1;
 125
 126         if ((asn & HARDWARE_ASN_MASK) >= MAX_ASN) {
 127                 tbiap();
 128                 imb();
 129                 next = (asn & ~HARDWARE_ASN_MASK) + ASN_FIRST_VERSION;
 130         }
 131         cpu_last_asn(cpu) = next;
 132         return next;
 133 }
 134
 135 __EXTERN_INLINE void
 136 ev5_switch_mm(struct mm_struct *prev_mm, struct mm_struct *next_mm,
 137               struct task_struct *next)
 138 {
 139         /* Check if our ASN is of an older version, and thus invalid. */
 140         unsigned long asn;
 141         unsigned long mmc;
 142         long cpu = smp_processor_id();
 143
 144 #ifdef CONFIG_SMP
 145         cpu_data[cpu].asn_lock = 1;
 146         barrier();
 147 #endif
 148         asn = cpu_last_asn(cpu);
 149         mmc = next_mm->context[cpu];
 150         if ((mmc ^ asn) & ~HARDWARE_ASN_MASK) {
 151                 mmc = __get_new_mm_context(next_mm, cpu);
 152                 next_mm->context[cpu] = mmc;
 153         }
 154 #ifdef CONFIG_SMP
 155         else
 156                 cpu_data[cpu].need_new_asn = 1;
 157 #endif
 158
 159         /* Always update the PCB ASN.  Another thread may have allocated
 160            a new mm->context (via flush_tlb_mm) without the ASN serial
 161            number wrapping.  We have no way to detect when this is needed.  */
 162         task_thread_info(next)->pcb.asn = mmc & HARDWARE_ASN_MASK;
 163 }
 164
 165 __EXTERN_INLINE void
 166 ev4_switch_mm(struct mm_struct *prev_mm, struct mm_struct *next_mm,
 167               struct task_struct *next)
 168 {
 169         /* As described, ASN's are broken for TLB usage.  But we can
 170            optimize for switching between threads -- if the mm is
 171            unchanged from current we needn't flush.  */
 172         /* ??? May not be needed because EV4 PALcode recognizes that
 173            ASN's are broken and does a tbiap itself on swpctx, under
 174            the "Must set ASN or flush" rule.  At least this is true
 175            for a 1992 SRM, reports Joseph Martin (jmartin@hlo.dec.com).
 176            I'm going to leave this here anyway, just to Be Sure.  -- r~  */
 177         if (prev_mm != next_mm)
 178                 tbiap();
 179
 180         /* Do continue to allocate ASNs, because we can still use them
 181            to avoid flushing the icache.  */
 182         ev5_switch_mm(prev_mm, next_mm, next);
 183 }
 184
 185 extern void __load_new_mm_context(struct mm_struct *);
 186
 187 #ifdef CONFIG_SMP
 188 #define check_mmu_context()                                     \
 189 do {                                                            \
 190         int cpu = smp_processor_id();                           \
 191         cpu_data[cpu].asn_lock = 0;                             \
 192         barrier();                                              \
 193         if (cpu_data[cpu].need_new_asn) {                       \
 194                 struct mm_struct * mm = current->active_mm;     \
 195                 cpu_data[cpu].need_new_asn = 0;                 \
 196                 if (!mm->context[cpu])                  \
 197                         __load_new_mm_context(mm);              \
 198         }                                                       \
 199 } while(0)
 200 #else
 201 #define check_mmu_context()  do { } while(0)
 202 #endif
 203
 204 __EXTERN_INLINE void
 205 ev5_activate_mm(struct mm_struct *prev_mm, struct mm_struct *next_mm)
 206 {
 207         __load_new_mm_context(next_mm);
 208 }
 209
 210 __EXTERN_INLINE void
 211 ev4_activate_mm(struct mm_struct *prev_mm, struct mm_struct *next_mm)
 212 {
 213         __load_new_mm_context(next_mm);
 214         tbiap();
 215 }
 216
 217 #define deactivate_mm(tsk,mm)   do { } while (0)
 218
 219 #ifdef CONFIG_ALPHA_GENERIC
 220 # define switch_mm(a,b,c)       alpha_mv.mv_switch_mm((a),(b),(c))
 221 # define activate_mm(x,y)       alpha_mv.mv_activate_mm((x),(y))
 222 #else
 223 # ifdef CONFIG_ALPHA_EV4
 224 #  define switch_mm(a,b,c)      ev4_switch_mm((a),(b),(c))
 225 #  define activate_mm(x,y)      ev4_activate_mm((x),(y))
 226 # else
 227 #  define switch_mm(a,b,c)      ev5_switch_mm((a),(b),(c))
 228 #  define activate_mm(x,y)      ev5_activate_mm((x),(y))
 229 # endif
 230 #endif
 231
 232 static inline int
 233 init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 234 {
 235         int i;
 236
 237         for_each_online_cpu(i)
 238                 mm->context[i] = 0;
 239         if (tsk != current)
 240                 task_thread_info(tsk)->pcb.ptbr
 241                   = ((unsigned long)mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
 242         return 0;
 243 }
 244
 245 extern inline void
 246 destroy_context(struct mm_struct *mm)
 247 {
 248         /* Nothing to do.  */
 249 }
 250
 251 static inline void
 252 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 253 {
 254         task_thread_info(tsk)->pcb.ptbr
 255           = ((unsigned long)mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
 256 }
 257
 258 #ifdef __MMU_EXTERN_INLINE
 259 #undef __EXTERN_INLINE
 260 #undef __MMU_EXTERN_INLINE
 261 #endif
 262
 263 #endif /* __ALPHA_MMU_CONTEXT_H */