X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=drivers%2Flguest%2Fpage_tables.c;h=d93500f24fbb22e26ecd0316ed12289ed8b4b686;hb=801eb73f45371accc78ca9d6d22d647eeb722c11;hp=fb665611ccc24a5c8c73dda7e4b4b7846aa35255;hpb=1713608f280002d9ffc6de89d7de5cf367072d63;p=linux-2.6 diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index fb665611cc..d93500f24f 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -2,8 +2,8 @@ * previous encounters. It's functional, and as neat as it can be in the * circumstances, but be wary, for these things are subtle and break easily. * The Guest provides a virtual to physical mapping, but we can neither trust - * it nor use it: we verify and convert it here to point the hardware to the - * actual Guest pages when running the Guest. :*/ + * it nor use it: we verify and convert it here then point the CPU to the + * converted Guest pages when running the Guest. :*/ /* Copyright (C) Rusty Russell IBM Corporation 2006. * GPL v2 and any later version */ @@ -68,23 +68,23 @@ static DEFINE_PER_CPU(pte_t *, switcher_pte_pages); * page directory entry (PGD) for that address. Since we keep track of several * page tables, the "i" argument tells us which one we're interested in (it's * usually the current one). */ -static pgd_t *spgd_addr(struct lguest *lg, u32 i, unsigned long vaddr) +static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr) { unsigned int index = pgd_index(vaddr); /* We kill any Guest trying to touch the Switcher addresses. */ if (index >= SWITCHER_PGD_INDEX) { - kill_guest(lg, "attempt to access switcher pages"); + kill_guest(cpu, "attempt to access switcher pages"); index = 0; } /* Return a pointer index'th pgd entry for the i'th page table. */ - return &lg->pgdirs[i].pgdir[index]; + return &cpu->lg->pgdirs[i].pgdir[index]; } /* This routine then takes the page directory entry returned above, which * contains the address of the page table entry (PTE) page. It then returns a * pointer to the PTE entry for the given address. */ -static pte_t *spte_addr(struct lguest *lg, pgd_t spgd, unsigned long vaddr) +static pte_t *spte_addr(pgd_t spgd, unsigned long vaddr) { pte_t *page = __va(pgd_pfn(spgd) << PAGE_SHIFT); /* You should never call this if the PGD entry wasn't valid */ @@ -100,13 +100,17 @@ static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr) return cpu->lg->pgdirs[cpu->cpu_pgd].gpgdir + index * sizeof(pgd_t); } -static unsigned long gpte_addr(struct lguest *lg, - pgd_t gpgd, unsigned long vaddr) +static unsigned long gpte_addr(pgd_t gpgd, unsigned long vaddr) { unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); return gpage + ((vaddr>>PAGE_SHIFT) % PTRS_PER_PTE) * sizeof(pte_t); } +/*:*/ + +/*M:014 get_pfn is slow; it takes the mmap sem and calls get_user_pages. We + * could probably try to grab batches of pages here as an optimization + * (ie. pre-faulting). :*/ /*H:350 This routine takes a page number given by the Guest and converts it to * an actual, physical page number. It can fail for several reasons: the @@ -114,8 +118,8 @@ static unsigned long gpte_addr(struct lguest *lg, * and the page is read-only, or the write flag was set and the page was * shared so had to be copied, but we ran out of memory. * - * This holds a reference to the page, so release_pte() is careful to - * put that back. */ + * This holds a reference to the page, so release_pte() is careful to put that + * back. */ static unsigned long get_pfn(unsigned long virtpfn, int write) { struct page *page; @@ -138,7 +142,7 @@ static unsigned long get_pfn(unsigned long virtpfn, int write) * entry can be a little tricky. The flags are (almost) the same, but the * Guest PTE contains a virtual page number: the CPU needs the real page * number. */ -static pte_t gpte_to_spte(struct lguest *lg, pte_t gpte, int write) +static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write) { unsigned long pfn, base, flags; @@ -149,7 +153,7 @@ static pte_t gpte_to_spte(struct lguest *lg, pte_t gpte, int write) flags = (pte_flags(gpte) & ~_PAGE_GLOBAL); /* The Guest's pages are offset inside the Launcher. */ - base = (unsigned long)lg->mem_base / PAGE_SIZE; + base = (unsigned long)cpu->lg->mem_base / PAGE_SIZE; /* We need a temporary "unsigned long" variable to hold the answer from * get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't @@ -157,7 +161,7 @@ static pte_t gpte_to_spte(struct lguest *lg, pte_t gpte, int write) * page, given the virtual number. */ pfn = get_pfn(base + pte_pfn(gpte), write); if (pfn == -1UL) { - kill_guest(lg, "failed to get page %lu", pte_pfn(gpte)); + kill_guest(cpu, "failed to get page %lu", pte_pfn(gpte)); /* When we destroy the Guest, we'll go through the shadow page * tables and release_pte() them. Make sure we don't think * this one is valid! */ @@ -177,17 +181,18 @@ static void release_pte(pte_t pte) } /*:*/ -static void check_gpte(struct lguest *lg, pte_t gpte) +static void check_gpte(struct lg_cpu *cpu, pte_t gpte) { - if ((pte_flags(gpte) & (_PAGE_PWT|_PAGE_PSE)) - || pte_pfn(gpte) >= lg->pfn_limit) - kill_guest(lg, "bad page table entry"); + if ((pte_flags(gpte) & _PAGE_PSE) || + pte_pfn(gpte) >= cpu->lg->pfn_limit) + kill_guest(cpu, "bad page table entry"); } -static void check_gpgd(struct lguest *lg, pgd_t gpgd) +static void check_gpgd(struct lg_cpu *cpu, pgd_t gpgd) { - if ((pgd_flags(gpgd) & ~_PAGE_TABLE) || pgd_pfn(gpgd) >= lg->pfn_limit) - kill_guest(lg, "bad page directory entry"); + if ((pgd_flags(gpgd) & ~_PAGE_TABLE) || + (pgd_pfn(gpgd) >= cpu->lg->pfn_limit)) + kill_guest(cpu, "bad page directory entry"); } /*H:330 @@ -207,27 +212,26 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) unsigned long gpte_ptr; pte_t gpte; pte_t *spte; - struct lguest *lg = cpu->lg; /* First step: get the top-level Guest page table entry. */ - gpgd = lgread(lg, gpgd_addr(cpu, vaddr), pgd_t); + gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); /* Toplevel not present? We can't map it in. */ if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) return 0; /* Now look at the matching shadow entry. */ - spgd = spgd_addr(lg, cpu->cpu_pgd, vaddr); + spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) { /* No shadow entry: allocate a new shadow PTE page. */ unsigned long ptepage = get_zeroed_page(GFP_KERNEL); /* This is not really the Guest's fault, but killing it is * simple for this corner case. */ if (!ptepage) { - kill_guest(lg, "out of memory allocating pte page"); + kill_guest(cpu, "out of memory allocating pte page"); return 0; } /* We check that the Guest pgd is OK. */ - check_gpgd(lg, gpgd); + check_gpgd(cpu, gpgd); /* And we copy the flags to the shadow PGD entry. The page * number in the shadow PGD is the page we just allocated. */ *spgd = __pgd(__pa(ptepage) | pgd_flags(gpgd)); @@ -235,8 +239,8 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) /* OK, now we look at the lower level in the Guest page table: keep its * address, because we might update it later. */ - gpte_ptr = gpte_addr(lg, gpgd, vaddr); - gpte = lgread(lg, gpte_ptr, pte_t); + gpte_ptr = gpte_addr(gpgd, vaddr); + gpte = lgread(cpu, gpte_ptr, pte_t); /* If this page isn't in the Guest page tables, we can't page it in. */ if (!(pte_flags(gpte) & _PAGE_PRESENT)) @@ -253,7 +257,7 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) /* Check that the Guest PTE flags are OK, and the page number is below * the pfn_limit (ie. not mapping the Launcher binary). */ - check_gpte(lg, gpte); + check_gpte(cpu, gpte); /* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */ gpte = pte_mkyoung(gpte); @@ -261,7 +265,7 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) gpte = pte_mkdirty(gpte); /* Get the pointer to the shadow PTE entry we're going to set. */ - spte = spte_addr(lg, *spgd, vaddr); + spte = spte_addr(*spgd, vaddr); /* If there was a valid shadow PTE entry here before, we release it. * This can happen with a write to a previously read-only entry. */ release_pte(*spte); @@ -269,17 +273,17 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) /* If this is a write, we insist that the Guest page is writable (the * final arg to gpte_to_spte()). */ if (pte_dirty(gpte)) - *spte = gpte_to_spte(lg, gpte, 1); + *spte = gpte_to_spte(cpu, gpte, 1); else /* If this is a read, don't set the "writable" bit in the page * table entry, even if the Guest says it's writable. That way * we will come back here when a write does actually occur, so * we can update the Guest's _PAGE_DIRTY flag. */ - *spte = gpte_to_spte(lg, pte_wrprotect(gpte), 0); + *spte = gpte_to_spte(cpu, pte_wrprotect(gpte), 0); /* Finally, we write the Guest PTE entry back: we've set the * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */ - lgwrite(lg, gpte_ptr, pte_t, gpte); + lgwrite(cpu, gpte_ptr, pte_t, gpte); /* The fault is fixed, the page table is populated, the mapping * manipulated, the result returned and the code complete. A small @@ -304,13 +308,13 @@ static int page_writable(struct lg_cpu *cpu, unsigned long vaddr) unsigned long flags; /* Look at the current top level entry: is it present? */ - spgd = spgd_addr(cpu->lg, cpu->cpu_pgd, vaddr); + spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) return 0; /* Check the flags on the pte entry itself: it must be present and * writable. */ - flags = pte_flags(*(spte_addr(cpu->lg, *spgd, vaddr))); + flags = pte_flags(*(spte_addr(*spgd, vaddr))); return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW); } @@ -321,7 +325,7 @@ static int page_writable(struct lg_cpu *cpu, unsigned long vaddr) void pin_page(struct lg_cpu *cpu, unsigned long vaddr) { if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2)) - kill_guest(cpu->lg, "bad stack page %#lx", vaddr); + kill_guest(cpu, "bad stack page %#lx", vaddr); } /*H:450 If we chase down the release_pgd() code, it looks like this: */ @@ -373,14 +377,14 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) pte_t gpte; /* First step: get the top-level Guest page table entry. */ - gpgd = lgread(cpu->lg, gpgd_addr(cpu, vaddr), pgd_t); + gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); /* Toplevel not present? We can't map it in. */ if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) - kill_guest(cpu->lg, "Bad address %#lx", vaddr); + kill_guest(cpu, "Bad address %#lx", vaddr); - gpte = lgread(cpu->lg, gpte_addr(cpu->lg, gpgd, vaddr), pte_t); + gpte = lgread(cpu, gpte_addr(gpgd, vaddr), pte_t); if (!(pte_flags(gpte) & _PAGE_PRESENT)) - kill_guest(cpu->lg, "Bad address %#lx", vaddr); + kill_guest(cpu, "Bad address %#lx", vaddr); return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK); } @@ -392,7 +396,7 @@ static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable) { unsigned int i; for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) - if (lg->pgdirs[i].gpgdir == pgtable) + if (lg->pgdirs[i].pgdir && lg->pgdirs[i].gpgdir == pgtable) break; return i; } @@ -405,16 +409,16 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, int *blank_pgdir) { unsigned int next; - struct lguest *lg = cpu->lg; /* We pick one entry at random to throw out. Choosing the Least * Recently Used might be better, but this is easy. */ - next = random32() % ARRAY_SIZE(lg->pgdirs); + next = random32() % ARRAY_SIZE(cpu->lg->pgdirs); /* If it's never been allocated at all before, try now. */ - if (!lg->pgdirs[next].pgdir) { - lg->pgdirs[next].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL); + if (!cpu->lg->pgdirs[next].pgdir) { + cpu->lg->pgdirs[next].pgdir = + (pgd_t *)get_zeroed_page(GFP_KERNEL); /* If the allocation fails, just keep using the one we have */ - if (!lg->pgdirs[next].pgdir) + if (!cpu->lg->pgdirs[next].pgdir) next = cpu->cpu_pgd; else /* This is a blank page, so there are no kernel @@ -422,9 +426,9 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, *blank_pgdir = 1; } /* Record which Guest toplevel this shadows. */ - lg->pgdirs[next].gpgdir = gpgdir; + cpu->lg->pgdirs[next].gpgdir = gpgdir; /* Release all the non-kernel mappings. */ - flush_user_mappings(lg, next); + flush_user_mappings(cpu->lg, next); return next; } @@ -437,13 +441,12 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) { int newpgdir, repin = 0; - struct lguest *lg = cpu->lg; /* Look to see if we have this one already. */ - newpgdir = find_pgdir(lg, pgtable); + newpgdir = find_pgdir(cpu->lg, pgtable); /* If not, we allocate or mug an existing one: if it's a fresh one, * repin gets set to 1. */ - if (newpgdir == ARRAY_SIZE(lg->pgdirs)) + if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs)) newpgdir = new_pgdir(cpu, pgtable, &repin); /* Change the current pgd index to the new one. */ cpu->cpu_pgd = newpgdir; @@ -500,24 +503,24 @@ void guest_pagetable_clear_all(struct lg_cpu *cpu) * _PAGE_ACCESSED then we can put a read-only PTE entry in immediately, and if * they set _PAGE_DIRTY then we can put a writable PTE entry in immediately. */ -static void do_set_pte(struct lguest *lg, int idx, +static void do_set_pte(struct lg_cpu *cpu, int idx, unsigned long vaddr, pte_t gpte) { /* Look up the matching shadow page directory entry. */ - pgd_t *spgd = spgd_addr(lg, idx, vaddr); + pgd_t *spgd = spgd_addr(cpu, idx, vaddr); /* If the top level isn't present, there's no entry to update. */ if (pgd_flags(*spgd) & _PAGE_PRESENT) { /* Otherwise, we start by releasing the existing entry. */ - pte_t *spte = spte_addr(lg, *spgd, vaddr); + pte_t *spte = spte_addr(*spgd, vaddr); release_pte(*spte); /* If they're setting this entry as dirty or accessed, we might * as well put that entry they've given us in now. This shaves * 10% off a copy-on-write micro-benchmark. */ if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) { - check_gpte(lg, gpte); - *spte = gpte_to_spte(lg, gpte, + check_gpte(cpu, gpte); + *spte = gpte_to_spte(cpu, gpte, pte_flags(gpte) & _PAGE_DIRTY); } else /* Otherwise kill it and we can demand_page() it in @@ -534,24 +537,24 @@ static void do_set_pte(struct lguest *lg, int idx, * all processes. So when the page table above that address changes, we update * all the page tables, not just the current one. This is rare. * - * The benefit is that when we have to track a new page table, we can copy keep - * all the kernel mappings. This speeds up context switch immensely. */ -void guest_set_pte(struct lguest *lg, + * The benefit is that when we have to track a new page table, we can keep all + * the kernel mappings. This speeds up context switch immensely. */ +void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir, unsigned long vaddr, pte_t gpte) { - /* Kernel mappings must be changed on all top levels. Slow, but - * doesn't happen often. */ - if (vaddr >= lg->kernel_address) { + /* Kernel mappings must be changed on all top levels. Slow, but doesn't + * happen often. */ + if (vaddr >= cpu->lg->kernel_address) { unsigned int i; - for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) - if (lg->pgdirs[i].pgdir) - do_set_pte(lg, i, vaddr, gpte); + for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++) + if (cpu->lg->pgdirs[i].pgdir) + do_set_pte(cpu, i, vaddr, gpte); } else { /* Is this page table one we have a shadow for? */ - int pgdir = find_pgdir(lg, gpgdir); - if (pgdir != ARRAY_SIZE(lg->pgdirs)) + int pgdir = find_pgdir(cpu->lg, gpgdir); + if (pgdir != ARRAY_SIZE(cpu->lg->pgdirs)) /* If so, do the update. */ - do_set_pte(lg, pgdir, vaddr, gpte); + do_set_pte(cpu, pgdir, vaddr, gpte); } } @@ -602,21 +605,23 @@ int init_guest_pagetable(struct lguest *lg, unsigned long pgtable) } /* When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ -void page_table_guest_data_init(struct lguest *lg) +void page_table_guest_data_init(struct lg_cpu *cpu) { /* We get the kernel address: above this is all kernel memory. */ - if (get_user(lg->kernel_address, &lg->lguest_data->kernel_address) + if (get_user(cpu->lg->kernel_address, + &cpu->lg->lguest_data->kernel_address) /* We tell the Guest that it can't use the top 4MB of virtual * addresses used by the Switcher. */ - || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem) - || put_user(lg->pgdirs[0].gpgdir, &lg->lguest_data->pgdir)) - kill_guest(lg, "bad guest page %p", lg->lguest_data); + || put_user(4U*1024*1024, &cpu->lg->lguest_data->reserve_mem) + || put_user(cpu->lg->pgdirs[0].gpgdir, &cpu->lg->lguest_data->pgdir)) + kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); /* In flush_user_mappings() we loop from 0 to * "pgd_index(lg->kernel_address)". This assumes it won't hit the * Switcher mappings, so check that now. */ - if (pgd_index(lg->kernel_address) >= SWITCHER_PGD_INDEX) - kill_guest(lg, "bad kernel address %#lx", lg->kernel_address); + if (pgd_index(cpu->lg->kernel_address) >= SWITCHER_PGD_INDEX) + kill_guest(cpu, "bad kernel address %#lx", + cpu->lg->kernel_address); } /* When a Guest dies, our cleanup is fairly simple. */ @@ -646,7 +651,7 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) /* Make the last PGD entry for this Guest point to the Switcher's PTE * page for this CPU (with appropriate flags). */ - switcher_pgd = __pgd(__pa(switcher_pte_page) | _PAGE_KERNEL); + switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL); cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd; @@ -658,7 +663,7 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) * page is already mapped there, we don't have to copy them out * again. */ pfn = __pa(cpu->regs_page) >> PAGE_SHIFT; - regs_pte = pfn_pte(pfn, __pgprot(_PAGE_KERNEL)); + regs_pte = pfn_pte(pfn, __pgprot(__PAGE_KERNEL)); switcher_pte_page[(unsigned long)pages/PAGE_SIZE%PTRS_PER_PTE] = regs_pte; } /*:*/ @@ -704,12 +709,11 @@ static __init void populate_switcher_pte_page(unsigned int cpu, /* We've made it through the page table code. Perhaps our tired brains are * still processing the details, or perhaps we're simply glad it's over. * - * If nothing else, note that all this complexity in juggling shadow page - * tables in sync with the Guest's page tables is for one reason: for most - * Guests this page table dance determines how bad performance will be. This - * is why Xen uses exotic direct Guest pagetable manipulation, and why both - * Intel and AMD have implemented shadow page table support directly into - * hardware. + * If nothing else, note that all this complexity in juggling shadow page tables + * in sync with the Guest's page tables is for one reason: for most Guests this + * page table dance determines how bad performance will be. This is why Xen + * uses exotic direct Guest pagetable manipulation, and why both Intel and AMD + * have implemented shadow page table support directly into hardware. * * There is just one file remaining in the Host. */