ref: 21b501c27faa36e413b09b594717f8669ce4183e
dir: /sys/src/9/xen/mmu.c/
#include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "io.h" int paemode; uvlong *xenpdpt; /* this needs to go in Mach for multiprocessor guest */ #define LOG(a) #define PUTMMULOG(a) #define MFN(pa) (patomfn[(pa)>>PGSHIFT]) #define MAPPN(x) (paemode? matopfn[*(uvlong*)(&x)>>PGSHIFT]<<PGSHIFT : matopfn[(x)>>PGSHIFT]<<PGSHIFT) /* note: pdb must already be pinned */ static void taskswitch(Page *pdb, ulong stack) { HYPERVISOR_stack_switch(KDSEL, stack); mmuflushtlb(pdb); } void mmuflushtlb(Page *pdb) { int s, i; if(!paemode){ if(pdb) xenptswitch(pdb->pa); else xenptswitch(PADDR(m->pdb)); }else{ if(pdb){ s = splhi(); for(i = 0; i < 3; i++){ xenupdate((ulong*)&xenpdpt[i], pdb->pa | PTEVALID); pdb = pdb->next; } splx(s); }else{ s = splhi(); for(i = 0; i < 3; i++) xenupdatema((ulong*)&xenpdpt[i], ((uvlong*)m->pdb)[i]); splx(s); } xentlbflush(); } } /* * On processors that support it, we set the PTEGLOBAL bit in * page table and page directory entries that map kernel memory. * Doing this tells the processor not to bother flushing them * from the TLB when doing the TLB flush associated with a * context switch (write to CR3). Since kernel memory mappings * are never removed, this is safe. (If we ever remove kernel memory * mappings, we can do a full flush by turning off the PGE bit in CR4, * writing to CR3, and then turning the PGE bit back on.) * * See also mmukmap below. * * Processor support for the PTEGLOBAL bit is enabled in devarch.c. */ static void memglobal(void) { int i, j; ulong *pde, *pte; /* only need to do this once, on bootstrap processor */ if(m->machno != 0) return; if(!m->havepge) return; pde = m->pdb; for(i=512; i<1024; i++){ /* 512: start at entry for virtual 0x80000000 */ if(pde[i] & PTEVALID){ pde[i] |= PTEGLOBAL; if(!(pde[i] & PTESIZE)){ pte = KADDR(pde[i]&~(BY2PG-1)); for(j=0; j<1024; j++) if(pte[j] & PTEVALID) pte[j] |= PTEGLOBAL; } } } } ulong mmumapframe(ulong va, ulong mfn) { ulong *pte, pdbx; uvlong ma; /* * map machine frame number to a virtual address. * When called the pagedir and page table exist, we just * need to fill in a page table entry. */ ma = ((uvlong)mfn<<PGSHIFT) | PTEVALID|PTEWRITE; pdbx = PDX(va); pte = KADDR(MAPPN(PDB(m->pdb,va)[pdbx])); xenupdatema(&pte[PTX(va)], ma); return va; } void mmumapcpu0(void) { ulong *pdb, *pte, va, pa, pdbx; if(strstr(xenstart->magic, "x86_32p")) paemode = 1; hypervisor_virt_start = paemode ? 0xF5800000 : 0xFC000000; patomfn = (ulong*)xenstart->mfn_list; matopfn = (ulong*)hypervisor_virt_start; /* Xen bug ? can't touch top entry in PDPT */ if(paemode) hypervisor_virt_start = 0xC0000000; /* * map CPU0MACH at MACHADDR. * When called the pagedir and page table exist, we just * need to fill in a page table entry. */ pdb = (ulong*)xenstart->pt_base; va = MACHADDR; pa = PADDR(CPU0MACH) | PTEVALID|PTEWRITE; pdbx = PDX(va); pdb = PDB(pdb, va); pte = KADDR(MAPPN(pdb[pdbx])); xenupdate(&pte[PTX(va)], pa); } void mmuinit(void) { ulong *pte, npgs, pa; if(paemode){ int i; xenpdpt = (uvlong*)m->pdb; m->pdb = xspanalloc(32, 32, 0); /* clear "reserved" bits in initial page directory pointers -- Xen bug? */ for(i = 0; i < 4; i++) ((uvlong*)m->pdb)[i] = xenpdpt[i] & ~0x1E6LL; } /* * So far only memory up to xentop is mapped, map the rest. * We cant use large pages because our contiguous PA space * is not necessarily contiguous in MA. */ npgs = conf.mem[0].npage; for(pa=conf.mem[0].base; npgs; npgs--, pa+=BY2PG) { pte = mmuwalk(m->pdb, (ulong)KADDR(pa), 2, 1); if(!pte) panic("mmuinit"); xenupdate(pte, pa|PTEVALID|PTEWRITE); } memglobal(); #ifdef we_may_eventually_want_this /* make kernel text unwritable */ for(x = KTZERO; x < (ulong)etext; x += BY2PG){ p = mmuwalk(m->pdb, x, 2, 0); if(p == nil) panic("mmuinit"); *p &= ~PTEWRITE; } #endif taskswitch(0, (ulong)m + BY2PG); } void flushmmu(void) { int s; s = splhi(); up->newtlb = 1; mmuswitch(up); splx(s); } static ulong* mmupdb(Page *pg, ulong va) { int i; for(i = PAX(va); i > 0; i -= 2) pg = pg->next; return (ulong*)pg->va; } /* this can be called with an active pdb, so use Xen calls to zero it out. */ static void mmuptefree(Proc* proc) { ulong *pdb, va; Page **last, *page; if(proc->mmupdb && proc->mmuused){ last = &proc->mmuused; for(page = *last; page; page = page->next){ /* this is no longer a pte page so make it readwrite */ va = page->daddr; pdb = mmupdb(proc->mmupdb, va); xenupdatema(&pdb[PDX(va)], 0); xenptunpin(page->va); last = &page->next; } *last = proc->mmufree; proc->mmufree = proc->mmuused; proc->mmuused = 0; } } void mmuswitch(Proc* proc) { //ulong *pdb; if(proc->newtlb){ mmuptefree(proc); proc->newtlb = 0; } if(proc->mmupdb){ //XXX doesn't work for some reason, but it's not needed for uniprocessor //pdb = (ulong*)proc->mmupdb->va; //xenupdate(&pdb[PDX(MACHADDR)], m->pdb[PDX(MACHADDR)]); taskswitch(proc->mmupdb, (ulong)(proc->kstack+KSTACK)); } else taskswitch(0, (ulong)(proc->kstack+KSTACK)); } void mmurelease(Proc* proc) { Page *page, *next; /* * Release any pages allocated for a page directory base or page-tables * for this process: * switch to the prototype pdb for this processor (m->pdb); * call mmuptefree() to place all pages used for page-tables (proc->mmuused) * onto the process' free list (proc->mmufree). This has the side-effect of * cleaning any user entries in the pdb (proc->mmupdb); * if there's a pdb put it in the cache of pre-initialised pdb's * for this processor (m->pdbpool) or on the process' free list; * finally, place any pages freed back into the free pool (palloc). * This routine is only called from sched() with palloc locked. */ taskswitch(0, (ulong)m + BY2PG); mmuptefree(proc); if((page = proc->mmupdb) != 0){ proc->mmupdb = 0; while(page){ next = page->next; /* its not a page table anymore, mark it rw */ xenptunpin(page->va); if(paemode || m->pdbcnt > 10){ page->next = proc->mmufree; proc->mmufree = page; } else{ page->next = m->pdbpool; m->pdbpool = page; m->pdbcnt++; } page = next; } } freepages(proc->mmufree, nil, 0); proc->mmufree = nil; } static Page* mmupdballoc(ulong va, void *mpdb) { int s; Page *page; Page *badpages, *pg; s = splhi(); /* * All page tables must be read-only. We will mark them * readwrite later when we free them and they are no * longer used as page tables. */ if(m->pdbpool == 0){ spllo(); badpages = 0; for (;;) { page = newpage(0, 0, 0); page->va = VA(kmap(page)); if(mpdb) memmove((void*)page->va, mpdb, BY2PG); else memset((void*)page->va, 0, BY2PG); if (xenpgdpin(page->va)) break; /* * XXX Plan 9 is a bit lax about putting pages on the free list when they are * still mapped (r/w) by some process's page table. From Plan 9's point * of view this is safe because the any such process will have up->newtlb set, * so the mapping will be cleared before the process is dispatched. But the Xen * hypervisor has no way of knowing this, so it refuses to pin the page for use * as a pagetable. */ if(0) print("bad pgdpin %lux va %lux copy %lux %s\n", MFN(PADDR(page->va)), va, (ulong)mpdb, up? up->text: ""); page->next = badpages; badpages = page; } while (badpages != 0) { pg = badpages; badpages = badpages->next; putpage(pg); } } else{ page = m->pdbpool; m->pdbpool = page->next; m->pdbcnt--; if (!xenpgdpin(page->va)) panic("xenpgdpin"); } splx(s); page->next = 0; return page; } void checkmmu(ulong va, ulong pa) { ulong *pdb, *pte; int pdbx; if(up->mmupdb == 0) return; pdb = mmupdb(up->mmupdb, va); pdbx = PDX(va); if(MAPPN(pdb[pdbx]) == 0){ /* okay to be empty - will fault and get filled */ return; } pte = KADDR(MAPPN(pdb[pdbx])); if(MAPPN(pte[PTX(va)]) != pa){ if(!paemode) print("%ld %s: va=0x%08lux pa=0x%08lux pte=0x%08lux (0x%08lux)\n", up->pid, up->text, va, pa, pte[PTX(va)], MAPPN(pte[PTX(va)])); else print("%ld %s: va=0x%08lux pa=0x%08lux pte=0x%16llux (0x%08lux)\n", up->pid, up->text, va, pa, *(uvlong*)&pte[PTX(va)], MAPPN(pte[PTX(va)])); } } void putmmu(ulong va, ulong pa, Page*) { int pdbx; Page *page; Page *badpages, *pg; ulong *pdb, *pte; int i, s; PUTMMULOG(dprint("putmmu va %lux pa %lux\n", va, pa);) if(up->mmupdb == 0){ if(!paemode) up->mmupdb = mmupdballoc(va, m->pdb); else { page = 0; for(i = 4; i >= 0; i -= 2){ if(m->pdb[i]) pg = mmupdballoc(va, KADDR(MAPPN(m->pdb[i]))); else pg = mmupdballoc(va, 0); pg->next = page; page = pg; } up->mmupdb = page; } } pdb = mmupdb(up->mmupdb, va); pdbx = PDX(va); if(PPN(pdb[pdbx]) == 0){ PUTMMULOG(dprint("new pt page for index %d pdb %lux\n", pdbx, (ulong)pdb);) /* mark page as readonly before using as a page table */ if(up->mmufree == 0){ badpages = 0; for (;;) { page = newpage(1, 0, 0); page->va = VA(kmap(page)); if (xenptpin(page->va)) break; if(0) print("bad pin %lux va %lux %s\n", MFN(PADDR(page->va)), va, up->text); page->next = badpages; badpages = page; } while (badpages != 0) { pg = badpages; badpages = badpages->next; putpage(pg); } } else { page = up->mmufree; up->mmufree = page->next; memset((void*)page->va, 0, BY2PG); if (!xenptpin(page->va)) panic("xenptpin"); } xenupdate(&pdb[pdbx], page->pa|PTEVALID|PTEUSER|PTEWRITE); page->daddr = va; page->next = up->mmuused; up->mmuused = page; } pte = KADDR(MAPPN(pdb[pdbx])); PUTMMULOG(dprint("pte %lux index %lud old %lux new %lux mfn %lux\n", (ulong)pte, PTX(va), pte[PTX(va)], pa|PTEUSER, MFN(pa));) xenupdate(&pte[PTX(va)], pa|PTEUSER); s = splhi(); //XXX doesn't work for some reason, but it's not needed for uniprocessor //xenupdate(&pdb[PDX(MACHADDR)], m->pdb[PDX(MACHADDR)]); mmuflushtlb(up->mmupdb); splx(s); } ulong* mmuwalk(ulong* pdb, ulong va, int level, int create) { ulong pa, va2, *table; /* * Walk the page-table pointed to by pdb and return a pointer * to the entry for virtual address va at the requested level. * If the entry is invalid and create isn't requested then bail * out early. Otherwise, for the 2nd level walk, allocate a new * page-table page and register it in the 1st level. */ if(paemode){ pdb = &pdb[PAX(va)]; if(!(*pdb & PTEVALID)){ if(create == 0) return 0; panic("mmuwalk: missing pgdir ptr for va=%lux\n", va); } pdb = KADDR(MAPPN(*pdb)); } table = &pdb[PDX(va)]; if(!(*table & PTEVALID) && create == 0) return 0; switch(level){ default: return 0; case 1: return table; case 2: if(*table & PTESIZE) panic("mmuwalk2: va %luX entry %luX\n", va, *table); if(!(*table & PTEVALID)){ va2 = (ulong)xspanalloc(BY2PG, BY2PG, 0); pa = PADDR(va2); xenptpin(va2); xenupdate(table, pa|PTEWRITE|PTEVALID); } table = KADDR(MAPPN(*table)); return &table[PTX(va)]; } } int mmukmapsync(ulong va) { USED(va); return 0; } /* * 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) { if(pa >= -KZERO) return 0; return -KZERO - pa; }