FreeBSD/Linux Kernel Cross Reference
sys/mtx/mmu.c
1 #include "u.h"
2 #include "../port/lib.h"
3 #include "mem.h"
4 #include "dat.h"
5 #include "fns.h"
6 #include "io.h"
7
8 /*
9 * We have one page table per processor.
10 *
11 * Different processes are distinguished via the VSID field in
12 * the segment registers. As flushing the entire page table is an
13 * expensive operation, we implement an aging algorithm for
14 * mmu pids, with a background kproc to purge stale pids en mass.
15 *
16 * This needs modifications to run on a multiprocessor.
17 */
18
19 static ulong ptabsize; /* number of bytes in page table */
20 static ulong ptabmask; /* hash mask */
21
22 /*
23 * VSID is 24 bits. 3 are required to distinguish segments in user
24 * space (kernel space only uses the BATs). pid 0 is reserved.
25 * The top 2 bits of the pid are used as a `color' for the background
26 * pid reclaimation algorithm.
27 */
28
29 enum {
30 PIDBASE = 1,
31 PIDBITS = 21,
32 COLBITS = 2,
33 PIDMAX = ((1<<PIDBITS)-1),
34 COLMASK = ((1<<COLBITS)-1),
35 };
36
37 #define VSID(pid, i) (((pid)<<3)|i)
38 #define PIDCOLOR(pid) ((pid)>>(PIDBITS-COLBITS))
39 #define PTECOL(color) PTE0(1, VSID(((color)<<(PIDBITS-COLBITS)), 0), 0, 0)
40
41 void
42 mmuinit(void)
43 {
44 int lhash, mem;
45 extern ulong memsize; /* passed in from ROM monitor */
46
47 if(ptabsize == 0) {
48 /* heuristically size the hash table */
49 lhash = 10;
50 mem = (1<<23);
51 while(mem < memsize) {
52 lhash++;
53 mem <<= 1;
54 }
55 ptabsize = (1<<(lhash+6));
56 ptabmask = (1<<lhash)-1;
57 }
58
59 m->ptabbase = (ulong)xspanalloc(ptabsize, 0, ptabsize);
60 putsdr1(PADDR(m->ptabbase) | (ptabmask>>10));
61 m->mmupid = PIDBASE;
62 m->sweepcolor = 0;
63 m->trigcolor = COLMASK;
64 }
65
66 static int
67 work(void*)
68 {
69 return PIDCOLOR(m->mmupid) == m->trigcolor;
70 }
71
72 void
73 mmusweep(void*)
74 {
75 Proc *p;
76 int i, x, sweepcolor;
77 ulong *ptab, *ptabend, ptecol;
78
79 for(;;) {
80 if(PIDCOLOR(m->mmupid) != m->trigcolor)
81 sleep(&m->sweepr, work, nil);
82
83 sweepcolor = m->sweepcolor;
84 x = splhi();
85 p = proctab(0);
86 for(i = 0; i < conf.nproc; i++, p++)
87 if(PIDCOLOR(p->mmupid) == sweepcolor)
88 p->mmupid = 0;
89 splx(x);
90
91 ptab = (ulong*)m->ptabbase;
92 ptabend = (ulong*)(m->ptabbase+ptabsize);
93 ptecol = PTECOL(sweepcolor);
94 while(ptab < ptabend) {
95 if((*ptab & PTECOL(3)) == ptecol)
96 *ptab = 0;
97 ptab += 2;
98 }
99 tlbflushall();
100
101 m->sweepcolor = (sweepcolor+1) & COLMASK;
102 m->trigcolor = (m->trigcolor+1) & COLMASK;
103 }
104 }
105
106 int
107 newmmupid(void)
108 {
109 int pid, newcolor;
110
111 pid = m->mmupid++;
112 if(m->mmupid > PIDMAX)
113 m->mmupid = PIDBASE;
114 newcolor = PIDCOLOR(m->mmupid);
115 if(newcolor != PIDCOLOR(pid)) {
116 if(newcolor == m->sweepcolor) {
117 /* desperation time. can't block here. punt to fault/putmmu */
118 print("newmmupid: %uld: no free mmu pids\n", up->pid);
119 if(m->mmupid == PIDBASE)
120 m->mmupid = PIDMAX;
121 else
122 m->mmupid--;
123 pid = 0;
124 }
125 else if(newcolor == m->trigcolor)
126 wakeup(&m->sweepr);
127 }
128 up->mmupid = pid;
129 return pid;
130 }
131
132 void
133 flushmmu(void)
134 {
135 int x;
136
137 x = splhi();
138 up->newtlb = 1;
139 mmuswitch(up);
140 splx(x);
141 }
142
143 /*
144 * called with splhi
145 */
146 void
147 mmuswitch(Proc *p)
148 {
149 int i, mp;
150
151 if(p->kp) {
152 for(i = 0; i < 8; i++)
153 putsr(i<<28, 0);
154 return;
155 }
156
157 if(p->newtlb) {
158 p->mmupid = 0;
159 p->newtlb = 0;
160 }
161 mp = p->mmupid;
162 if(mp == 0)
163 mp = newmmupid();
164
165 for(i = 0; i < 8; i++)
166 putsr(i<<28, VSID(mp, i)|BIT(1)|BIT(2));
167 }
168
169 void
170 mmurelease(Proc* p)
171 {
172 p->mmupid = 0;
173 }
174
175 void
176 putmmu(ulong va, ulong pa, Page *pg)
177 {
178 int mp;
179 char *ctl;
180 ulong *p, *ep, *q, pteg;
181 ulong vsid, ptehi, x, hash;
182
183 /*
184 * If mmupid is 0, mmuswitch/newmmupid was unable to assign us
185 * a pid, hence we faulted. Keep calling sched() until the mmusweep
186 * proc catches up, and we are able to get a pid.
187 */
188 while((mp = up->mmupid) == 0)
189 sched();
190
191 vsid = VSID(mp, va>>28);
192 hash = (vsid ^ (va>>12)&0xffff) & ptabmask;
193 ptehi = PTE0(1, vsid, 0, va);
194
195 pteg = m->ptabbase + BY2PTEG*hash;
196 p = (ulong*)pteg;
197 ep = (ulong*)(pteg+BY2PTEG);
198 q = nil;
199 tlbflush(va);
200 while(p < ep) {
201 x = p[0];
202 if(x == ptehi) {
203 q = p;
204 break;
205 }
206 if(q == nil && (x & BIT(0)) == 0)
207 q = p;
208 p += 2;
209 }
210 if(q == nil) {
211 q = (ulong*)(pteg+m->slotgen);
212 m->slotgen = (m->slotgen + BY2PTE) & (BY2PTEG-1);
213 }
214 q[0] = ptehi;
215 q[1] = pa;
216 sync();
217
218 ctl = &pg->cachectl[m->machno];
219 switch(*ctl) {
220 case PG_NEWCOL:
221 default:
222 panic("putmmu: %d\n", *ctl);
223 break;
224 case PG_NOFLUSH:
225 break;
226 case PG_TXTFLUSH:
227 dcflush((void*)pg->va, BY2PG);
228 icflush((void*)pg->va, BY2PG);
229 *ctl = PG_NOFLUSH;
230 break;
231 }
232 }
233
234 void
235 checkmmu(ulong, ulong)
236 {
237 }
238
239 void
240 countpagerefs(ulong*, int)
241 {
242 }
243
244 /*
245 * Return the number of bytes that can be accessed via KADDR(pa).
246 * If pa is not a valid argument to KADDR, return 0.
247 */
248 ulong
249 cankaddr(ulong pa)
250 {
251 ulong kzero;
252
253 kzero = -KZERO;
254 if(pa >= kzero)
255 return 0;
256 return kzero - pa;
257 }
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