ref: b76a78c1a1973d62ff32c030e29b3ffcc560e50d
dir: /sys/src/9/mtx/mmu.c/
#include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "io.h" /* * We have one page table per processor. * * Different processes are distinguished via the VSID field in * the segment registers. As flushing the entire page table is an * expensive operation, we implement an aging algorithm for * mmu pids, with a background kproc to purge stale pids en mass. * * This needs modifications to run on a multiprocessor. */ static ulong ptabsize; /* number of bytes in page table */ static ulong ptabmask; /* hash mask */ /* * VSID is 24 bits. 3 are required to distinguish segments in user * space (kernel space only uses the BATs). pid 0 is reserved. * The top 2 bits of the pid are used as a `color' for the background * pid reclaimation algorithm. */ enum { PIDBASE = 1, PIDBITS = 21, COLBITS = 2, PIDMAX = ((1<<PIDBITS)-1), COLMASK = ((1<<COLBITS)-1), }; #define VSID(pid, i) (((pid)<<3)|i) #define PIDCOLOR(pid) ((pid)>>(PIDBITS-COLBITS)) #define PTECOL(color) PTE0(1, VSID(((color)<<(PIDBITS-COLBITS)), 0), 0, 0) void mmuinit(void) { int lhash, mem; extern ulong memsize; /* passed in from ROM monitor */ if(ptabsize == 0) { /* heuristically size the hash table */ lhash = 10; mem = (1<<23); while(mem < memsize) { lhash++; mem <<= 1; } ptabsize = (1<<(lhash+6)); ptabmask = (1<<lhash)-1; } m->ptabbase = (ulong)xspanalloc(ptabsize, 0, ptabsize); putsdr1(PADDR(m->ptabbase) | (ptabmask>>10)); m->mmupid = PIDBASE; m->sweepcolor = 0; m->trigcolor = COLMASK; } static int work(void*) { return PIDCOLOR(m->mmupid) == m->trigcolor; } void mmusweep(void*) { Proc *p; int i, x, sweepcolor; ulong *ptab, *ptabend, ptecol; while(waserror()) ; for(;;) { if(PIDCOLOR(m->mmupid) != m->trigcolor) sleep(&m->sweepr, work, nil); sweepcolor = m->sweepcolor; x = splhi(); p = proctab(0); for(i = 0; i < conf.nproc; i++, p++) if(PIDCOLOR(p->mmupid) == sweepcolor) p->mmupid = 0; splx(x); ptab = (ulong*)m->ptabbase; ptabend = (ulong*)(m->ptabbase+ptabsize); ptecol = PTECOL(sweepcolor); while(ptab < ptabend) { if((*ptab & PTECOL(3)) == ptecol) *ptab = 0; ptab += 2; } tlbflushall(); m->sweepcolor = (sweepcolor+1) & COLMASK; m->trigcolor = (m->trigcolor+1) & COLMASK; } } int newmmupid(void) { int pid, newcolor; pid = m->mmupid++; if(m->mmupid > PIDMAX) m->mmupid = PIDBASE; newcolor = PIDCOLOR(m->mmupid); if(newcolor != PIDCOLOR(pid)) { if(newcolor == m->sweepcolor) { /* desperation time. can't block here. punt to fault/putmmu */ print("newmmupid: %uld: no free mmu pids\n", up->pid); if(m->mmupid == PIDBASE) m->mmupid = PIDMAX; else m->mmupid--; pid = 0; } else if(newcolor == m->trigcolor) wakeup(&m->sweepr); } up->mmupid = pid; return pid; } void flushmmu(void) { int x; x = splhi(); up->newtlb = 1; mmuswitch(up); splx(x); } /* * called with splhi */ void mmuswitch(Proc *p) { int i, mp; if(p->kp) { for(i = 0; i < 8; i++) putsr(i<<28, 0); return; } if(p->newtlb) { p->mmupid = 0; p->newtlb = 0; } mp = p->mmupid; if(mp == 0) mp = newmmupid(); for(i = 0; i < 8; i++) putsr(i<<28, VSID(mp, i)|BIT(1)|BIT(2)); } void mmurelease(Proc* p) { p->mmupid = 0; } void putmmu(uintptr va, uintptr pa, Page *pg) { int mp; ulong *p, *ep, *q, pteg; ulong vsid, ptehi, x, hash; /* * If mmupid is 0, mmuswitch/newmmupid was unable to assign us * a pid, hence we faulted. Keep calling sched() until the mmusweep * proc catches up, and we are able to get a pid. */ while((mp = up->mmupid) == 0) sched(); vsid = VSID(mp, va>>28); hash = (vsid ^ (va>>12)&0xffff) & ptabmask; ptehi = PTE0(1, vsid, 0, va); pteg = m->ptabbase + BY2PTEG*hash; p = (ulong*)pteg; ep = (ulong*)(pteg+BY2PTEG); q = nil; tlbflush(va); while(p < ep) { x = p[0]; if(x == ptehi) { q = p; break; } if(q == nil && (x & BIT(0)) == 0) q = p; p += 2; } if(q == nil) { q = (ulong*)(pteg+m->slotgen); m->slotgen = (m->slotgen + BY2PTE) & (BY2PTEG-1); } q[0] = ptehi; q[1] = pa; sync(); if(pg->txtflush & (1<<m->machno)){ dcflush((void*)pg->va, BY2PG); icflush((void*)pg->va, BY2PG); pg->txtflush &= ~(1<<m->machno); } } void checkmmu(uintptr, uintptr) { } void countpagerefs(ulong*, int) { } /* * Return the number of bytes that can be accessed via KADDR(pa). * If pa is not a valid argument to KADDR, return 0. */ ulong cankaddr(ulong pa) { ulong kzero; kzero = -KZERO; if(pa >= kzero) return 0; return kzero - pa; }