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f938d2c8 RR |
1 | /*P:700 The pagetable code, on the other hand, still shows the scars of |
2 | * previous encounters. It's functional, and as neat as it can be in the | |
3 | * circumstances, but be wary, for these things are subtle and break easily. | |
4 | * The Guest provides a virtual to physical mapping, but we can neither trust | |
a6bd8e13 RR |
5 | * it nor use it: we verify and convert it here then point the CPU to the |
6 | * converted Guest pages when running the Guest. :*/ | |
f938d2c8 RR |
7 | |
8 | /* Copyright (C) Rusty Russell IBM Corporation 2006. | |
d7e28ffe RR |
9 | * GPL v2 and any later version */ |
10 | #include <linux/mm.h> | |
11 | #include <linux/types.h> | |
12 | #include <linux/spinlock.h> | |
13 | #include <linux/random.h> | |
14 | #include <linux/percpu.h> | |
15 | #include <asm/tlbflush.h> | |
47436aa4 | 16 | #include <asm/uaccess.h> |
58a24566 | 17 | #include <asm/bootparam.h> |
d7e28ffe RR |
18 | #include "lg.h" |
19 | ||
f56a384e RR |
20 | /*M:008 We hold reference to pages, which prevents them from being swapped. |
21 | * It'd be nice to have a callback in the "struct mm_struct" when Linux wants | |
22 | * to swap out. If we had this, and a shrinker callback to trim PTE pages, we | |
23 | * could probably consider launching Guests as non-root. :*/ | |
24 | ||
bff672e6 RR |
25 | /*H:300 |
26 | * The Page Table Code | |
27 | * | |
28 | * We use two-level page tables for the Guest. If you're not entirely | |
29 | * comfortable with virtual addresses, physical addresses and page tables then | |
e1e72965 RR |
30 | * I recommend you review arch/x86/lguest/boot.c's "Page Table Handling" (with |
31 | * diagrams!). | |
bff672e6 RR |
32 | * |
33 | * The Guest keeps page tables, but we maintain the actual ones here: these are | |
34 | * called "shadow" page tables. Which is a very Guest-centric name: these are | |
35 | * the real page tables the CPU uses, although we keep them up to date to | |
36 | * reflect the Guest's. (See what I mean about weird naming? Since when do | |
37 | * shadows reflect anything?) | |
38 | * | |
39 | * Anyway, this is the most complicated part of the Host code. There are seven | |
40 | * parts to this: | |
e1e72965 RR |
41 | * (i) Looking up a page table entry when the Guest faults, |
42 | * (ii) Making sure the Guest stack is mapped, | |
43 | * (iii) Setting up a page table entry when the Guest tells us one has changed, | |
bff672e6 | 44 | * (iv) Switching page tables, |
e1e72965 | 45 | * (v) Flushing (throwing away) page tables, |
bff672e6 RR |
46 | * (vi) Mapping the Switcher when the Guest is about to run, |
47 | * (vii) Setting up the page tables initially. | |
48 | :*/ | |
49 | ||
bff672e6 RR |
50 | |
51 | /* 1024 entries in a page table page maps 1024 pages: 4MB. The Switcher is | |
52 | * conveniently placed at the top 4MB, so it uses a separate, complete PTE | |
53 | * page. */ | |
df29f43e | 54 | #define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1) |
d7e28ffe | 55 | |
bff672e6 RR |
56 | /* We actually need a separate PTE page for each CPU. Remember that after the |
57 | * Switcher code itself comes two pages for each CPU, and we don't want this | |
58 | * CPU's guest to see the pages of any other CPU. */ | |
df29f43e | 59 | static DEFINE_PER_CPU(pte_t *, switcher_pte_pages); |
d7e28ffe RR |
60 | #define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu) |
61 | ||
e1e72965 RR |
62 | /*H:320 The page table code is curly enough to need helper functions to keep it |
63 | * clear and clean. | |
bff672e6 | 64 | * |
df29f43e | 65 | * There are two functions which return pointers to the shadow (aka "real") |
bff672e6 RR |
66 | * page tables. |
67 | * | |
68 | * spgd_addr() takes the virtual address and returns a pointer to the top-level | |
e1e72965 RR |
69 | * page directory entry (PGD) for that address. Since we keep track of several |
70 | * page tables, the "i" argument tells us which one we're interested in (it's | |
bff672e6 | 71 | * usually the current one). */ |
382ac6b3 | 72 | static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr) |
d7e28ffe | 73 | { |
df29f43e | 74 | unsigned int index = pgd_index(vaddr); |
d7e28ffe | 75 | |
bff672e6 | 76 | /* We kill any Guest trying to touch the Switcher addresses. */ |
d7e28ffe | 77 | if (index >= SWITCHER_PGD_INDEX) { |
382ac6b3 | 78 | kill_guest(cpu, "attempt to access switcher pages"); |
d7e28ffe RR |
79 | index = 0; |
80 | } | |
bff672e6 | 81 | /* Return a pointer index'th pgd entry for the i'th page table. */ |
382ac6b3 | 82 | return &cpu->lg->pgdirs[i].pgdir[index]; |
d7e28ffe RR |
83 | } |
84 | ||
e1e72965 RR |
85 | /* This routine then takes the page directory entry returned above, which |
86 | * contains the address of the page table entry (PTE) page. It then returns a | |
87 | * pointer to the PTE entry for the given address. */ | |
2092aa27 | 88 | static pte_t *spte_addr(pgd_t spgd, unsigned long vaddr) |
d7e28ffe | 89 | { |
df29f43e | 90 | pte_t *page = __va(pgd_pfn(spgd) << PAGE_SHIFT); |
bff672e6 | 91 | /* You should never call this if the PGD entry wasn't valid */ |
df29f43e MZ |
92 | BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT)); |
93 | return &page[(vaddr >> PAGE_SHIFT) % PTRS_PER_PTE]; | |
d7e28ffe RR |
94 | } |
95 | ||
bff672e6 RR |
96 | /* These two functions just like the above two, except they access the Guest |
97 | * page tables. Hence they return a Guest address. */ | |
1713608f | 98 | static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr) |
d7e28ffe | 99 | { |
df29f43e | 100 | unsigned int index = vaddr >> (PGDIR_SHIFT); |
1713608f | 101 | return cpu->lg->pgdirs[cpu->cpu_pgd].gpgdir + index * sizeof(pgd_t); |
d7e28ffe RR |
102 | } |
103 | ||
934faab4 | 104 | static unsigned long gpte_addr(pgd_t gpgd, unsigned long vaddr) |
d7e28ffe | 105 | { |
df29f43e MZ |
106 | unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; |
107 | BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); | |
108 | return gpage + ((vaddr>>PAGE_SHIFT) % PTRS_PER_PTE) * sizeof(pte_t); | |
d7e28ffe | 109 | } |
a6bd8e13 RR |
110 | /*:*/ |
111 | ||
71a3f4ed RR |
112 | /*M:014 get_pfn is slow: we could probably try to grab batches of pages here as |
113 | * an optimization (ie. pre-faulting). :*/ | |
d7e28ffe | 114 | |
bff672e6 RR |
115 | /*H:350 This routine takes a page number given by the Guest and converts it to |
116 | * an actual, physical page number. It can fail for several reasons: the | |
117 | * virtual address might not be mapped by the Launcher, the write flag is set | |
118 | * and the page is read-only, or the write flag was set and the page was | |
119 | * shared so had to be copied, but we ran out of memory. | |
120 | * | |
a6bd8e13 RR |
121 | * This holds a reference to the page, so release_pte() is careful to put that |
122 | * back. */ | |
d7e28ffe RR |
123 | static unsigned long get_pfn(unsigned long virtpfn, int write) |
124 | { | |
125 | struct page *page; | |
71a3f4ed RR |
126 | |
127 | /* gup me one page at this address please! */ | |
128 | if (get_user_pages_fast(virtpfn << PAGE_SHIFT, 1, write, &page) == 1) | |
129 | return page_to_pfn(page); | |
130 | ||
bff672e6 | 131 | /* This value indicates failure. */ |
71a3f4ed | 132 | return -1UL; |
d7e28ffe RR |
133 | } |
134 | ||
bff672e6 RR |
135 | /*H:340 Converting a Guest page table entry to a shadow (ie. real) page table |
136 | * entry can be a little tricky. The flags are (almost) the same, but the | |
137 | * Guest PTE contains a virtual page number: the CPU needs the real page | |
138 | * number. */ | |
382ac6b3 | 139 | static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write) |
d7e28ffe | 140 | { |
df29f43e | 141 | unsigned long pfn, base, flags; |
d7e28ffe | 142 | |
bff672e6 RR |
143 | /* The Guest sets the global flag, because it thinks that it is using |
144 | * PGE. We only told it to use PGE so it would tell us whether it was | |
145 | * flushing a kernel mapping or a userspace mapping. We don't actually | |
146 | * use the global bit, so throw it away. */ | |
df29f43e | 147 | flags = (pte_flags(gpte) & ~_PAGE_GLOBAL); |
bff672e6 | 148 | |
3c6b5bfa | 149 | /* The Guest's pages are offset inside the Launcher. */ |
382ac6b3 | 150 | base = (unsigned long)cpu->lg->mem_base / PAGE_SIZE; |
3c6b5bfa | 151 | |
bff672e6 RR |
152 | /* We need a temporary "unsigned long" variable to hold the answer from |
153 | * get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't | |
154 | * fit in spte.pfn. get_pfn() finds the real physical number of the | |
155 | * page, given the virtual number. */ | |
df29f43e | 156 | pfn = get_pfn(base + pte_pfn(gpte), write); |
d7e28ffe | 157 | if (pfn == -1UL) { |
382ac6b3 | 158 | kill_guest(cpu, "failed to get page %lu", pte_pfn(gpte)); |
bff672e6 RR |
159 | /* When we destroy the Guest, we'll go through the shadow page |
160 | * tables and release_pte() them. Make sure we don't think | |
161 | * this one is valid! */ | |
df29f43e | 162 | flags = 0; |
d7e28ffe | 163 | } |
df29f43e MZ |
164 | /* Now we assemble our shadow PTE from the page number and flags. */ |
165 | return pfn_pte(pfn, __pgprot(flags)); | |
d7e28ffe RR |
166 | } |
167 | ||
bff672e6 | 168 | /*H:460 And to complete the chain, release_pte() looks like this: */ |
df29f43e | 169 | static void release_pte(pte_t pte) |
d7e28ffe | 170 | { |
71a3f4ed | 171 | /* Remember that get_user_pages_fast() took a reference to the page, in |
bff672e6 | 172 | * get_pfn()? We have to put it back now. */ |
df29f43e MZ |
173 | if (pte_flags(pte) & _PAGE_PRESENT) |
174 | put_page(pfn_to_page(pte_pfn(pte))); | |
d7e28ffe | 175 | } |
bff672e6 | 176 | /*:*/ |
d7e28ffe | 177 | |
382ac6b3 | 178 | static void check_gpte(struct lg_cpu *cpu, pte_t gpte) |
d7e28ffe | 179 | { |
31f4b46e AD |
180 | if ((pte_flags(gpte) & _PAGE_PSE) || |
181 | pte_pfn(gpte) >= cpu->lg->pfn_limit) | |
382ac6b3 | 182 | kill_guest(cpu, "bad page table entry"); |
d7e28ffe RR |
183 | } |
184 | ||
382ac6b3 | 185 | static void check_gpgd(struct lg_cpu *cpu, pgd_t gpgd) |
d7e28ffe | 186 | { |
382ac6b3 GOC |
187 | if ((pgd_flags(gpgd) & ~_PAGE_TABLE) || |
188 | (pgd_pfn(gpgd) >= cpu->lg->pfn_limit)) | |
189 | kill_guest(cpu, "bad page directory entry"); | |
d7e28ffe RR |
190 | } |
191 | ||
bff672e6 | 192 | /*H:330 |
e1e72965 | 193 | * (i) Looking up a page table entry when the Guest faults. |
bff672e6 RR |
194 | * |
195 | * We saw this call in run_guest(): when we see a page fault in the Guest, we | |
196 | * come here. That's because we only set up the shadow page tables lazily as | |
197 | * they're needed, so we get page faults all the time and quietly fix them up | |
198 | * and return to the Guest without it knowing. | |
199 | * | |
200 | * If we fixed up the fault (ie. we mapped the address), this routine returns | |
e1e72965 | 201 | * true. Otherwise, it was a real fault and we need to tell the Guest. */ |
1713608f | 202 | int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) |
d7e28ffe | 203 | { |
df29f43e MZ |
204 | pgd_t gpgd; |
205 | pgd_t *spgd; | |
d7e28ffe | 206 | unsigned long gpte_ptr; |
df29f43e MZ |
207 | pte_t gpte; |
208 | pte_t *spte; | |
d7e28ffe | 209 | |
bff672e6 | 210 | /* First step: get the top-level Guest page table entry. */ |
382ac6b3 | 211 | gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); |
bff672e6 | 212 | /* Toplevel not present? We can't map it in. */ |
df29f43e | 213 | if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) |
d7e28ffe RR |
214 | return 0; |
215 | ||
bff672e6 | 216 | /* Now look at the matching shadow entry. */ |
382ac6b3 | 217 | spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); |
df29f43e | 218 | if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) { |
bff672e6 | 219 | /* No shadow entry: allocate a new shadow PTE page. */ |
d7e28ffe | 220 | unsigned long ptepage = get_zeroed_page(GFP_KERNEL); |
bff672e6 RR |
221 | /* This is not really the Guest's fault, but killing it is |
222 | * simple for this corner case. */ | |
d7e28ffe | 223 | if (!ptepage) { |
382ac6b3 | 224 | kill_guest(cpu, "out of memory allocating pte page"); |
d7e28ffe RR |
225 | return 0; |
226 | } | |
bff672e6 | 227 | /* We check that the Guest pgd is OK. */ |
382ac6b3 | 228 | check_gpgd(cpu, gpgd); |
bff672e6 RR |
229 | /* And we copy the flags to the shadow PGD entry. The page |
230 | * number in the shadow PGD is the page we just allocated. */ | |
df29f43e | 231 | *spgd = __pgd(__pa(ptepage) | pgd_flags(gpgd)); |
d7e28ffe RR |
232 | } |
233 | ||
bff672e6 RR |
234 | /* OK, now we look at the lower level in the Guest page table: keep its |
235 | * address, because we might update it later. */ | |
934faab4 | 236 | gpte_ptr = gpte_addr(gpgd, vaddr); |
382ac6b3 | 237 | gpte = lgread(cpu, gpte_ptr, pte_t); |
d7e28ffe | 238 | |
bff672e6 | 239 | /* If this page isn't in the Guest page tables, we can't page it in. */ |
df29f43e | 240 | if (!(pte_flags(gpte) & _PAGE_PRESENT)) |
d7e28ffe RR |
241 | return 0; |
242 | ||
bff672e6 RR |
243 | /* Check they're not trying to write to a page the Guest wants |
244 | * read-only (bit 2 of errcode == write). */ | |
df29f43e | 245 | if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW)) |
d7e28ffe RR |
246 | return 0; |
247 | ||
e1e72965 | 248 | /* User access to a kernel-only page? (bit 3 == user access) */ |
df29f43e | 249 | if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER)) |
d7e28ffe RR |
250 | return 0; |
251 | ||
bff672e6 RR |
252 | /* Check that the Guest PTE flags are OK, and the page number is below |
253 | * the pfn_limit (ie. not mapping the Launcher binary). */ | |
382ac6b3 | 254 | check_gpte(cpu, gpte); |
e1e72965 | 255 | |
bff672e6 | 256 | /* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */ |
df29f43e | 257 | gpte = pte_mkyoung(gpte); |
d7e28ffe | 258 | if (errcode & 2) |
df29f43e | 259 | gpte = pte_mkdirty(gpte); |
d7e28ffe | 260 | |
bff672e6 | 261 | /* Get the pointer to the shadow PTE entry we're going to set. */ |
2092aa27 | 262 | spte = spte_addr(*spgd, vaddr); |
bff672e6 RR |
263 | /* If there was a valid shadow PTE entry here before, we release it. |
264 | * This can happen with a write to a previously read-only entry. */ | |
d7e28ffe RR |
265 | release_pte(*spte); |
266 | ||
bff672e6 RR |
267 | /* If this is a write, we insist that the Guest page is writable (the |
268 | * final arg to gpte_to_spte()). */ | |
df29f43e | 269 | if (pte_dirty(gpte)) |
382ac6b3 | 270 | *spte = gpte_to_spte(cpu, gpte, 1); |
df29f43e | 271 | else |
bff672e6 RR |
272 | /* If this is a read, don't set the "writable" bit in the page |
273 | * table entry, even if the Guest says it's writable. That way | |
e1e72965 RR |
274 | * we will come back here when a write does actually occur, so |
275 | * we can update the Guest's _PAGE_DIRTY flag. */ | |
382ac6b3 | 276 | *spte = gpte_to_spte(cpu, pte_wrprotect(gpte), 0); |
d7e28ffe | 277 | |
bff672e6 RR |
278 | /* Finally, we write the Guest PTE entry back: we've set the |
279 | * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */ | |
382ac6b3 | 280 | lgwrite(cpu, gpte_ptr, pte_t, gpte); |
bff672e6 | 281 | |
e1e72965 RR |
282 | /* The fault is fixed, the page table is populated, the mapping |
283 | * manipulated, the result returned and the code complete. A small | |
284 | * delay and a trace of alliteration are the only indications the Guest | |
285 | * has that a page fault occurred at all. */ | |
d7e28ffe RR |
286 | return 1; |
287 | } | |
288 | ||
e1e72965 RR |
289 | /*H:360 |
290 | * (ii) Making sure the Guest stack is mapped. | |
bff672e6 | 291 | * |
e1e72965 RR |
292 | * Remember that direct traps into the Guest need a mapped Guest kernel stack. |
293 | * pin_stack_pages() calls us here: we could simply call demand_page(), but as | |
294 | * we've seen that logic is quite long, and usually the stack pages are already | |
295 | * mapped, so it's overkill. | |
bff672e6 RR |
296 | * |
297 | * This is a quick version which answers the question: is this virtual address | |
298 | * mapped by the shadow page tables, and is it writable? */ | |
1713608f | 299 | static int page_writable(struct lg_cpu *cpu, unsigned long vaddr) |
d7e28ffe | 300 | { |
df29f43e | 301 | pgd_t *spgd; |
d7e28ffe RR |
302 | unsigned long flags; |
303 | ||
e1e72965 | 304 | /* Look at the current top level entry: is it present? */ |
382ac6b3 | 305 | spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); |
df29f43e | 306 | if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) |
d7e28ffe RR |
307 | return 0; |
308 | ||
bff672e6 RR |
309 | /* Check the flags on the pte entry itself: it must be present and |
310 | * writable. */ | |
2092aa27 | 311 | flags = pte_flags(*(spte_addr(*spgd, vaddr))); |
df29f43e | 312 | |
d7e28ffe RR |
313 | return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW); |
314 | } | |
315 | ||
bff672e6 RR |
316 | /* So, when pin_stack_pages() asks us to pin a page, we check if it's already |
317 | * in the page tables, and if not, we call demand_page() with error code 2 | |
318 | * (meaning "write"). */ | |
1713608f | 319 | void pin_page(struct lg_cpu *cpu, unsigned long vaddr) |
d7e28ffe | 320 | { |
1713608f | 321 | if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2)) |
382ac6b3 | 322 | kill_guest(cpu, "bad stack page %#lx", vaddr); |
d7e28ffe RR |
323 | } |
324 | ||
bff672e6 | 325 | /*H:450 If we chase down the release_pgd() code, it looks like this: */ |
df29f43e | 326 | static void release_pgd(struct lguest *lg, pgd_t *spgd) |
d7e28ffe | 327 | { |
bff672e6 | 328 | /* If the entry's not present, there's nothing to release. */ |
df29f43e | 329 | if (pgd_flags(*spgd) & _PAGE_PRESENT) { |
d7e28ffe | 330 | unsigned int i; |
bff672e6 RR |
331 | /* Converting the pfn to find the actual PTE page is easy: turn |
332 | * the page number into a physical address, then convert to a | |
333 | * virtual address (easy for kernel pages like this one). */ | |
df29f43e | 334 | pte_t *ptepage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); |
bff672e6 | 335 | /* For each entry in the page, we might need to release it. */ |
df29f43e | 336 | for (i = 0; i < PTRS_PER_PTE; i++) |
d7e28ffe | 337 | release_pte(ptepage[i]); |
bff672e6 | 338 | /* Now we can free the page of PTEs */ |
d7e28ffe | 339 | free_page((long)ptepage); |
e1e72965 | 340 | /* And zero out the PGD entry so we never release it twice. */ |
df29f43e | 341 | *spgd = __pgd(0); |
d7e28ffe RR |
342 | } |
343 | } | |
344 | ||
e1e72965 RR |
345 | /*H:445 We saw flush_user_mappings() twice: once from the flush_user_mappings() |
346 | * hypercall and once in new_pgdir() when we re-used a top-level pgdir page. | |
347 | * It simply releases every PTE page from 0 up to the Guest's kernel address. */ | |
d7e28ffe RR |
348 | static void flush_user_mappings(struct lguest *lg, int idx) |
349 | { | |
350 | unsigned int i; | |
bff672e6 | 351 | /* Release every pgd entry up to the kernel's address. */ |
47436aa4 | 352 | for (i = 0; i < pgd_index(lg->kernel_address); i++) |
d7e28ffe RR |
353 | release_pgd(lg, lg->pgdirs[idx].pgdir + i); |
354 | } | |
355 | ||
e1e72965 RR |
356 | /*H:440 (v) Flushing (throwing away) page tables, |
357 | * | |
358 | * The Guest has a hypercall to throw away the page tables: it's used when a | |
359 | * large number of mappings have been changed. */ | |
1713608f | 360 | void guest_pagetable_flush_user(struct lg_cpu *cpu) |
d7e28ffe | 361 | { |
bff672e6 | 362 | /* Drop the userspace part of the current page table. */ |
1713608f | 363 | flush_user_mappings(cpu->lg, cpu->cpu_pgd); |
d7e28ffe | 364 | } |
bff672e6 | 365 | /*:*/ |
d7e28ffe | 366 | |
47436aa4 | 367 | /* We walk down the guest page tables to get a guest-physical address */ |
1713608f | 368 | unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) |
47436aa4 RR |
369 | { |
370 | pgd_t gpgd; | |
371 | pte_t gpte; | |
372 | ||
373 | /* First step: get the top-level Guest page table entry. */ | |
382ac6b3 | 374 | gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); |
47436aa4 | 375 | /* Toplevel not present? We can't map it in. */ |
6afbdd05 | 376 | if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) { |
382ac6b3 | 377 | kill_guest(cpu, "Bad address %#lx", vaddr); |
6afbdd05 RR |
378 | return -1UL; |
379 | } | |
47436aa4 | 380 | |
382ac6b3 | 381 | gpte = lgread(cpu, gpte_addr(gpgd, vaddr), pte_t); |
47436aa4 | 382 | if (!(pte_flags(gpte) & _PAGE_PRESENT)) |
382ac6b3 | 383 | kill_guest(cpu, "Bad address %#lx", vaddr); |
47436aa4 RR |
384 | |
385 | return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK); | |
386 | } | |
387 | ||
bff672e6 RR |
388 | /* We keep several page tables. This is a simple routine to find the page |
389 | * table (if any) corresponding to this top-level address the Guest has given | |
390 | * us. */ | |
d7e28ffe RR |
391 | static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable) |
392 | { | |
393 | unsigned int i; | |
394 | for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) | |
4357bd94 | 395 | if (lg->pgdirs[i].pgdir && lg->pgdirs[i].gpgdir == pgtable) |
d7e28ffe RR |
396 | break; |
397 | return i; | |
398 | } | |
399 | ||
bff672e6 RR |
400 | /*H:435 And this is us, creating the new page directory. If we really do |
401 | * allocate a new one (and so the kernel parts are not there), we set | |
402 | * blank_pgdir. */ | |
1713608f | 403 | static unsigned int new_pgdir(struct lg_cpu *cpu, |
ee3db0f2 | 404 | unsigned long gpgdir, |
d7e28ffe RR |
405 | int *blank_pgdir) |
406 | { | |
407 | unsigned int next; | |
408 | ||
bff672e6 RR |
409 | /* We pick one entry at random to throw out. Choosing the Least |
410 | * Recently Used might be better, but this is easy. */ | |
382ac6b3 | 411 | next = random32() % ARRAY_SIZE(cpu->lg->pgdirs); |
bff672e6 | 412 | /* If it's never been allocated at all before, try now. */ |
382ac6b3 GOC |
413 | if (!cpu->lg->pgdirs[next].pgdir) { |
414 | cpu->lg->pgdirs[next].pgdir = | |
415 | (pgd_t *)get_zeroed_page(GFP_KERNEL); | |
bff672e6 | 416 | /* If the allocation fails, just keep using the one we have */ |
382ac6b3 | 417 | if (!cpu->lg->pgdirs[next].pgdir) |
1713608f | 418 | next = cpu->cpu_pgd; |
d7e28ffe | 419 | else |
bff672e6 RR |
420 | /* This is a blank page, so there are no kernel |
421 | * mappings: caller must map the stack! */ | |
d7e28ffe RR |
422 | *blank_pgdir = 1; |
423 | } | |
bff672e6 | 424 | /* Record which Guest toplevel this shadows. */ |
382ac6b3 | 425 | cpu->lg->pgdirs[next].gpgdir = gpgdir; |
d7e28ffe | 426 | /* Release all the non-kernel mappings. */ |
382ac6b3 | 427 | flush_user_mappings(cpu->lg, next); |
d7e28ffe RR |
428 | |
429 | return next; | |
430 | } | |
431 | ||
bff672e6 RR |
432 | /*H:430 (iv) Switching page tables |
433 | * | |
e1e72965 RR |
434 | * Now we've seen all the page table setting and manipulation, let's see what |
435 | * what happens when the Guest changes page tables (ie. changes the top-level | |
436 | * pgdir). This occurs on almost every context switch. */ | |
4665ac8e | 437 | void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) |
d7e28ffe RR |
438 | { |
439 | int newpgdir, repin = 0; | |
440 | ||
bff672e6 | 441 | /* Look to see if we have this one already. */ |
382ac6b3 | 442 | newpgdir = find_pgdir(cpu->lg, pgtable); |
bff672e6 RR |
443 | /* If not, we allocate or mug an existing one: if it's a fresh one, |
444 | * repin gets set to 1. */ | |
382ac6b3 | 445 | if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs)) |
1713608f | 446 | newpgdir = new_pgdir(cpu, pgtable, &repin); |
bff672e6 | 447 | /* Change the current pgd index to the new one. */ |
1713608f | 448 | cpu->cpu_pgd = newpgdir; |
bff672e6 | 449 | /* If it was completely blank, we map in the Guest kernel stack */ |
d7e28ffe | 450 | if (repin) |
4665ac8e | 451 | pin_stack_pages(cpu); |
d7e28ffe RR |
452 | } |
453 | ||
bff672e6 | 454 | /*H:470 Finally, a routine which throws away everything: all PGD entries in all |
e1e72965 RR |
455 | * the shadow page tables, including the Guest's kernel mappings. This is used |
456 | * when we destroy the Guest. */ | |
d7e28ffe RR |
457 | static void release_all_pagetables(struct lguest *lg) |
458 | { | |
459 | unsigned int i, j; | |
460 | ||
bff672e6 | 461 | /* Every shadow pagetable this Guest has */ |
d7e28ffe RR |
462 | for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) |
463 | if (lg->pgdirs[i].pgdir) | |
bff672e6 | 464 | /* Every PGD entry except the Switcher at the top */ |
d7e28ffe RR |
465 | for (j = 0; j < SWITCHER_PGD_INDEX; j++) |
466 | release_pgd(lg, lg->pgdirs[i].pgdir + j); | |
467 | } | |
468 | ||
bff672e6 RR |
469 | /* We also throw away everything when a Guest tells us it's changed a kernel |
470 | * mapping. Since kernel mappings are in every page table, it's easiest to | |
e1e72965 RR |
471 | * throw them all away. This traps the Guest in amber for a while as |
472 | * everything faults back in, but it's rare. */ | |
4665ac8e | 473 | void guest_pagetable_clear_all(struct lg_cpu *cpu) |
d7e28ffe | 474 | { |
4665ac8e | 475 | release_all_pagetables(cpu->lg); |
bff672e6 | 476 | /* We need the Guest kernel stack mapped again. */ |
4665ac8e | 477 | pin_stack_pages(cpu); |
d7e28ffe | 478 | } |
e1e72965 RR |
479 | /*:*/ |
480 | /*M:009 Since we throw away all mappings when a kernel mapping changes, our | |
481 | * performance sucks for guests using highmem. In fact, a guest with | |
482 | * PAGE_OFFSET 0xc0000000 (the default) and more than about 700MB of RAM is | |
483 | * usually slower than a Guest with less memory. | |
484 | * | |
485 | * This, of course, cannot be fixed. It would take some kind of... well, I | |
486 | * don't know, but the term "puissant code-fu" comes to mind. :*/ | |
d7e28ffe | 487 | |
bff672e6 RR |
488 | /*H:420 This is the routine which actually sets the page table entry for then |
489 | * "idx"'th shadow page table. | |
490 | * | |
491 | * Normally, we can just throw out the old entry and replace it with 0: if they | |
492 | * use it demand_page() will put the new entry in. We need to do this anyway: | |
493 | * The Guest expects _PAGE_ACCESSED to be set on its PTE the first time a page | |
494 | * is read from, and _PAGE_DIRTY when it's written to. | |
495 | * | |
496 | * But Avi Kivity pointed out that most Operating Systems (Linux included) set | |
497 | * these bits on PTEs immediately anyway. This is done to save the CPU from | |
498 | * having to update them, but it helps us the same way: if they set | |
499 | * _PAGE_ACCESSED then we can put a read-only PTE entry in immediately, and if | |
500 | * they set _PAGE_DIRTY then we can put a writable PTE entry in immediately. | |
501 | */ | |
382ac6b3 | 502 | static void do_set_pte(struct lg_cpu *cpu, int idx, |
df29f43e | 503 | unsigned long vaddr, pte_t gpte) |
d7e28ffe | 504 | { |
e1e72965 | 505 | /* Look up the matching shadow page directory entry. */ |
382ac6b3 | 506 | pgd_t *spgd = spgd_addr(cpu, idx, vaddr); |
bff672e6 RR |
507 | |
508 | /* If the top level isn't present, there's no entry to update. */ | |
df29f43e | 509 | if (pgd_flags(*spgd) & _PAGE_PRESENT) { |
bff672e6 | 510 | /* Otherwise, we start by releasing the existing entry. */ |
2092aa27 | 511 | pte_t *spte = spte_addr(*spgd, vaddr); |
d7e28ffe | 512 | release_pte(*spte); |
bff672e6 RR |
513 | |
514 | /* If they're setting this entry as dirty or accessed, we might | |
515 | * as well put that entry they've given us in now. This shaves | |
516 | * 10% off a copy-on-write micro-benchmark. */ | |
df29f43e | 517 | if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) { |
382ac6b3 GOC |
518 | check_gpte(cpu, gpte); |
519 | *spte = gpte_to_spte(cpu, gpte, | |
df29f43e | 520 | pte_flags(gpte) & _PAGE_DIRTY); |
d7e28ffe | 521 | } else |
e1e72965 RR |
522 | /* Otherwise kill it and we can demand_page() it in |
523 | * later. */ | |
df29f43e | 524 | *spte = __pte(0); |
d7e28ffe RR |
525 | } |
526 | } | |
527 | ||
bff672e6 RR |
528 | /*H:410 Updating a PTE entry is a little trickier. |
529 | * | |
530 | * We keep track of several different page tables (the Guest uses one for each | |
531 | * process, so it makes sense to cache at least a few). Each of these have | |
532 | * identical kernel parts: ie. every mapping above PAGE_OFFSET is the same for | |
533 | * all processes. So when the page table above that address changes, we update | |
534 | * all the page tables, not just the current one. This is rare. | |
535 | * | |
a6bd8e13 RR |
536 | * The benefit is that when we have to track a new page table, we can keep all |
537 | * the kernel mappings. This speeds up context switch immensely. */ | |
382ac6b3 | 538 | void guest_set_pte(struct lg_cpu *cpu, |
ee3db0f2 | 539 | unsigned long gpgdir, unsigned long vaddr, pte_t gpte) |
d7e28ffe | 540 | { |
a6bd8e13 RR |
541 | /* Kernel mappings must be changed on all top levels. Slow, but doesn't |
542 | * happen often. */ | |
382ac6b3 | 543 | if (vaddr >= cpu->lg->kernel_address) { |
d7e28ffe | 544 | unsigned int i; |
382ac6b3 GOC |
545 | for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++) |
546 | if (cpu->lg->pgdirs[i].pgdir) | |
547 | do_set_pte(cpu, i, vaddr, gpte); | |
d7e28ffe | 548 | } else { |
bff672e6 | 549 | /* Is this page table one we have a shadow for? */ |
382ac6b3 GOC |
550 | int pgdir = find_pgdir(cpu->lg, gpgdir); |
551 | if (pgdir != ARRAY_SIZE(cpu->lg->pgdirs)) | |
bff672e6 | 552 | /* If so, do the update. */ |
382ac6b3 | 553 | do_set_pte(cpu, pgdir, vaddr, gpte); |
d7e28ffe RR |
554 | } |
555 | } | |
556 | ||
bff672e6 | 557 | /*H:400 |
e1e72965 | 558 | * (iii) Setting up a page table entry when the Guest tells us one has changed. |
bff672e6 RR |
559 | * |
560 | * Just like we did in interrupts_and_traps.c, it makes sense for us to deal | |
561 | * with the other side of page tables while we're here: what happens when the | |
562 | * Guest asks for a page table to be updated? | |
563 | * | |
564 | * We already saw that demand_page() will fill in the shadow page tables when | |
565 | * needed, so we can simply remove shadow page table entries whenever the Guest | |
566 | * tells us they've changed. When the Guest tries to use the new entry it will | |
567 | * fault and demand_page() will fix it up. | |
568 | * | |
569 | * So with that in mind here's our code to to update a (top-level) PGD entry: | |
570 | */ | |
ee3db0f2 | 571 | void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 idx) |
d7e28ffe RR |
572 | { |
573 | int pgdir; | |
574 | ||
bff672e6 RR |
575 | /* The kernel seems to try to initialize this early on: we ignore its |
576 | * attempts to map over the Switcher. */ | |
d7e28ffe RR |
577 | if (idx >= SWITCHER_PGD_INDEX) |
578 | return; | |
579 | ||
bff672e6 | 580 | /* If they're talking about a page table we have a shadow for... */ |
ee3db0f2 | 581 | pgdir = find_pgdir(lg, gpgdir); |
d7e28ffe | 582 | if (pgdir < ARRAY_SIZE(lg->pgdirs)) |
bff672e6 | 583 | /* ... throw it away. */ |
d7e28ffe RR |
584 | release_pgd(lg, lg->pgdirs[pgdir].pgdir + idx); |
585 | } | |
586 | ||
58a24566 MZ |
587 | /* Once we know how much memory we have we can construct simple identity |
588 | * (which set virtual == physical) and linear mappings | |
589 | * which will get the Guest far enough into the boot to create its own. | |
590 | * | |
591 | * We lay them out of the way, just below the initrd (which is why we need to | |
592 | * know its size here). */ | |
593 | static unsigned long setup_pagetables(struct lguest *lg, | |
594 | unsigned long mem, | |
595 | unsigned long initrd_size) | |
596 | { | |
597 | pgd_t __user *pgdir; | |
598 | pte_t __user *linear; | |
599 | unsigned int mapped_pages, i, linear_pages, phys_linear; | |
600 | unsigned long mem_base = (unsigned long)lg->mem_base; | |
601 | ||
602 | /* We have mapped_pages frames to map, so we need | |
603 | * linear_pages page tables to map them. */ | |
604 | mapped_pages = mem / PAGE_SIZE; | |
605 | linear_pages = (mapped_pages + PTRS_PER_PTE - 1) / PTRS_PER_PTE; | |
606 | ||
607 | /* We put the toplevel page directory page at the top of memory. */ | |
608 | pgdir = (pgd_t *)(mem + mem_base - initrd_size - PAGE_SIZE); | |
609 | ||
610 | /* Now we use the next linear_pages pages as pte pages */ | |
611 | linear = (void *)pgdir - linear_pages * PAGE_SIZE; | |
612 | ||
613 | /* Linear mapping is easy: put every page's address into the | |
614 | * mapping in order. */ | |
615 | for (i = 0; i < mapped_pages; i++) { | |
616 | pte_t pte; | |
617 | pte = pfn_pte(i, __pgprot(_PAGE_PRESENT|_PAGE_RW|_PAGE_USER)); | |
618 | if (copy_to_user(&linear[i], &pte, sizeof(pte)) != 0) | |
619 | return -EFAULT; | |
620 | } | |
621 | ||
622 | /* The top level points to the linear page table pages above. | |
623 | * We setup the identity and linear mappings here. */ | |
624 | phys_linear = (unsigned long)linear - mem_base; | |
625 | for (i = 0; i < mapped_pages; i += PTRS_PER_PTE) { | |
626 | pgd_t pgd; | |
627 | pgd = __pgd((phys_linear + i * sizeof(pte_t)) | | |
628 | (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER)); | |
629 | ||
630 | if (copy_to_user(&pgdir[i / PTRS_PER_PTE], &pgd, sizeof(pgd)) | |
631 | || copy_to_user(&pgdir[pgd_index(PAGE_OFFSET) | |
632 | + i / PTRS_PER_PTE], | |
633 | &pgd, sizeof(pgd))) | |
634 | return -EFAULT; | |
635 | } | |
636 | ||
637 | /* We return the top level (guest-physical) address: remember where | |
638 | * this is. */ | |
639 | return (unsigned long)pgdir - mem_base; | |
640 | } | |
641 | ||
bff672e6 RR |
642 | /*H:500 (vii) Setting up the page tables initially. |
643 | * | |
644 | * When a Guest is first created, the Launcher tells us where the toplevel of | |
645 | * its first page table is. We set some things up here: */ | |
58a24566 | 646 | int init_guest_pagetable(struct lguest *lg) |
d7e28ffe | 647 | { |
58a24566 MZ |
648 | u64 mem; |
649 | u32 initrd_size; | |
650 | struct boot_params __user *boot = (struct boot_params *)lg->mem_base; | |
651 | ||
652 | /* Get the Guest memory size and the ramdisk size from the boot header | |
653 | * located at lg->mem_base (Guest address 0). */ | |
654 | if (copy_from_user(&mem, &boot->e820_map[0].size, sizeof(mem)) | |
655 | || get_user(initrd_size, &boot->hdr.ramdisk_size)) | |
656 | return -EFAULT; | |
657 | ||
bff672e6 RR |
658 | /* We start on the first shadow page table, and give it a blank PGD |
659 | * page. */ | |
58a24566 MZ |
660 | lg->pgdirs[0].gpgdir = setup_pagetables(lg, mem, initrd_size); |
661 | if (IS_ERR_VALUE(lg->pgdirs[0].gpgdir)) | |
662 | return lg->pgdirs[0].gpgdir; | |
1713608f GOC |
663 | lg->pgdirs[0].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL); |
664 | if (!lg->pgdirs[0].pgdir) | |
d7e28ffe | 665 | return -ENOMEM; |
1713608f | 666 | lg->cpus[0].cpu_pgd = 0; |
d7e28ffe RR |
667 | return 0; |
668 | } | |
669 | ||
47436aa4 | 670 | /* When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ |
382ac6b3 | 671 | void page_table_guest_data_init(struct lg_cpu *cpu) |
47436aa4 RR |
672 | { |
673 | /* We get the kernel address: above this is all kernel memory. */ | |
382ac6b3 GOC |
674 | if (get_user(cpu->lg->kernel_address, |
675 | &cpu->lg->lguest_data->kernel_address) | |
47436aa4 RR |
676 | /* We tell the Guest that it can't use the top 4MB of virtual |
677 | * addresses used by the Switcher. */ | |
382ac6b3 GOC |
678 | || put_user(4U*1024*1024, &cpu->lg->lguest_data->reserve_mem) |
679 | || put_user(cpu->lg->pgdirs[0].gpgdir, &cpu->lg->lguest_data->pgdir)) | |
680 | kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); | |
47436aa4 RR |
681 | |
682 | /* In flush_user_mappings() we loop from 0 to | |
683 | * "pgd_index(lg->kernel_address)". This assumes it won't hit the | |
684 | * Switcher mappings, so check that now. */ | |
382ac6b3 GOC |
685 | if (pgd_index(cpu->lg->kernel_address) >= SWITCHER_PGD_INDEX) |
686 | kill_guest(cpu, "bad kernel address %#lx", | |
687 | cpu->lg->kernel_address); | |
47436aa4 RR |
688 | } |
689 | ||
bff672e6 | 690 | /* When a Guest dies, our cleanup is fairly simple. */ |
d7e28ffe RR |
691 | void free_guest_pagetable(struct lguest *lg) |
692 | { | |
693 | unsigned int i; | |
694 | ||
bff672e6 | 695 | /* Throw away all page table pages. */ |
d7e28ffe | 696 | release_all_pagetables(lg); |
bff672e6 | 697 | /* Now free the top levels: free_page() can handle 0 just fine. */ |
d7e28ffe RR |
698 | for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) |
699 | free_page((long)lg->pgdirs[i].pgdir); | |
700 | } | |
701 | ||
bff672e6 RR |
702 | /*H:480 (vi) Mapping the Switcher when the Guest is about to run. |
703 | * | |
e1e72965 | 704 | * The Switcher and the two pages for this CPU need to be visible in the |
bff672e6 | 705 | * Guest (and not the pages for other CPUs). We have the appropriate PTE pages |
e1e72965 RR |
706 | * for each CPU already set up, we just need to hook them in now we know which |
707 | * Guest is about to run on this CPU. */ | |
0c78441c | 708 | void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) |
d7e28ffe | 709 | { |
df29f43e MZ |
710 | pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages); |
711 | pgd_t switcher_pgd; | |
712 | pte_t regs_pte; | |
a53a35a8 | 713 | unsigned long pfn; |
d7e28ffe | 714 | |
bff672e6 RR |
715 | /* Make the last PGD entry for this Guest point to the Switcher's PTE |
716 | * page for this CPU (with appropriate flags). */ | |
84f12e39 | 717 | switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL); |
df29f43e | 718 | |
1713608f | 719 | cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd; |
d7e28ffe | 720 | |
bff672e6 RR |
721 | /* We also change the Switcher PTE page. When we're running the Guest, |
722 | * we want the Guest's "regs" page to appear where the first Switcher | |
723 | * page for this CPU is. This is an optimization: when the Switcher | |
724 | * saves the Guest registers, it saves them into the first page of this | |
725 | * CPU's "struct lguest_pages": if we make sure the Guest's register | |
726 | * page is already mapped there, we don't have to copy them out | |
727 | * again. */ | |
a53a35a8 | 728 | pfn = __pa(cpu->regs_page) >> PAGE_SHIFT; |
84f12e39 | 729 | regs_pte = pfn_pte(pfn, __pgprot(__PAGE_KERNEL)); |
df29f43e | 730 | switcher_pte_page[(unsigned long)pages/PAGE_SIZE%PTRS_PER_PTE] = regs_pte; |
d7e28ffe | 731 | } |
bff672e6 | 732 | /*:*/ |
d7e28ffe RR |
733 | |
734 | static void free_switcher_pte_pages(void) | |
735 | { | |
736 | unsigned int i; | |
737 | ||
738 | for_each_possible_cpu(i) | |
739 | free_page((long)switcher_pte_page(i)); | |
740 | } | |
741 | ||
bff672e6 RR |
742 | /*H:520 Setting up the Switcher PTE page for given CPU is fairly easy, given |
743 | * the CPU number and the "struct page"s for the Switcher code itself. | |
744 | * | |
745 | * Currently the Switcher is less than a page long, so "pages" is always 1. */ | |
d7e28ffe RR |
746 | static __init void populate_switcher_pte_page(unsigned int cpu, |
747 | struct page *switcher_page[], | |
748 | unsigned int pages) | |
749 | { | |
750 | unsigned int i; | |
df29f43e | 751 | pte_t *pte = switcher_pte_page(cpu); |
d7e28ffe | 752 | |
bff672e6 | 753 | /* The first entries are easy: they map the Switcher code. */ |
d7e28ffe | 754 | for (i = 0; i < pages; i++) { |
df29f43e MZ |
755 | pte[i] = mk_pte(switcher_page[i], |
756 | __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)); | |
d7e28ffe RR |
757 | } |
758 | ||
bff672e6 | 759 | /* The only other thing we map is this CPU's pair of pages. */ |
d7e28ffe RR |
760 | i = pages + cpu*2; |
761 | ||
bff672e6 | 762 | /* First page (Guest registers) is writable from the Guest */ |
df29f43e MZ |
763 | pte[i] = pfn_pte(page_to_pfn(switcher_page[i]), |
764 | __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW)); | |
765 | ||
bff672e6 RR |
766 | /* The second page contains the "struct lguest_ro_state", and is |
767 | * read-only. */ | |
df29f43e MZ |
768 | pte[i+1] = pfn_pte(page_to_pfn(switcher_page[i+1]), |
769 | __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)); | |
d7e28ffe RR |
770 | } |
771 | ||
e1e72965 RR |
772 | /* We've made it through the page table code. Perhaps our tired brains are |
773 | * still processing the details, or perhaps we're simply glad it's over. | |
774 | * | |
a6bd8e13 RR |
775 | * If nothing else, note that all this complexity in juggling shadow page tables |
776 | * in sync with the Guest's page tables is for one reason: for most Guests this | |
777 | * page table dance determines how bad performance will be. This is why Xen | |
778 | * uses exotic direct Guest pagetable manipulation, and why both Intel and AMD | |
779 | * have implemented shadow page table support directly into hardware. | |
e1e72965 RR |
780 | * |
781 | * There is just one file remaining in the Host. */ | |
782 | ||
bff672e6 RR |
783 | /*H:510 At boot or module load time, init_pagetables() allocates and populates |
784 | * the Switcher PTE page for each CPU. */ | |
d7e28ffe RR |
785 | __init int init_pagetables(struct page **switcher_page, unsigned int pages) |
786 | { | |
787 | unsigned int i; | |
788 | ||
789 | for_each_possible_cpu(i) { | |
df29f43e | 790 | switcher_pte_page(i) = (pte_t *)get_zeroed_page(GFP_KERNEL); |
d7e28ffe RR |
791 | if (!switcher_pte_page(i)) { |
792 | free_switcher_pte_pages(); | |
793 | return -ENOMEM; | |
794 | } | |
795 | populate_switcher_pte_page(i, switcher_page, pages); | |
796 | } | |
797 | return 0; | |
798 | } | |
bff672e6 | 799 | /*:*/ |
d7e28ffe | 800 | |
bff672e6 | 801 | /* Cleaning up simply involves freeing the PTE page for each CPU. */ |
d7e28ffe RR |
802 | void free_pagetables(void) |
803 | { | |
804 | free_switcher_pte_pages(); | |
805 | } |