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 */
264