MMPagePool.cpp@ 61794

Last change on this file since 61794 was 58170, checked in by vboxsync, 9 years ago
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1	/* $Id: MMPagePool.cpp 58170 2015-10-12 09:27:14Z vboxsync $ */
2	/** @file
3	* MM - Memory Manager - Page Pool.
4	*/
5
6	/*
7	* Copyright (C) 2006-2015 Oracle Corporation
8	*
9	* This file is part of VirtualBox Open Source Edition (OSE), as
10	* available from http://www.virtualbox.org. This file is free software;
11	* you can redistribute it and/or modify it under the terms of the GNU
12	* General Public License (GPL) as published by the Free Software
13	* Foundation, in version 2 as it comes in the "COPYING" file of the
14	* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15	* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16	*/
17
18
19	/*********************************************************************************************************************************
20	* Header Files *
21	*********************************************************************************************************************************/
22	#define LOG_GROUP LOG_GROUP_MM_POOL
23	#include <VBox/vmm/mm.h>
24	#include <VBox/vmm/pgm.h>
25	#include <VBox/vmm/stam.h>
26	#include "MMInternal.h"
27	#include <VBox/vmm/vm.h>
28	#include <VBox/param.h>
29	#include <VBox/err.h>
30	#include <VBox/log.h>
31	#include "internal/pgm.h"
32	#include <iprt/alloc.h>
33	#include <iprt/assert.h>
34	#define USE_INLINE_ASM_BIT_OPS
35	#ifdef USE_INLINE_ASM_BIT_OPS
36	# include <iprt/asm.h>
37	#endif
38	#include <iprt/string.h>
39
40
41
42	/*********************************************************************************************************************************
43	* Internal Functions *
44	*********************************************************************************************************************************/
45	#ifdef IN_RING3
46	static void * mmR3PagePoolAlloc(PMMPAGEPOOL pPool);
47	static void mmR3PagePoolFree(PMMPAGEPOOL pPool, void *pv);
48	#endif
49
50
51	/**
52	* Initializes the page pool
53	*
54	* @return VBox status code.
55	* @param pVM The cross context VM structure.
56	* @thread The Emulation Thread.
57	*/
58	int mmR3PagePoolInit(PVM pVM)
59	{
60	AssertMsg(!pVM->mm.s.pPagePoolR3, ("Already initialized!\n"));
61
62	/*
63	* Allocate the pool structures.
64	*/
65	/** @todo @bugref{1865},@bugref{3202}: mapping the page pool page into ring-0.
66	* Need to change the ways we allocate it... */
67	AssertReleaseReturn(sizeof(pVM->mm.s.pPagePoolR3) + sizeof(pVM->mm.s.pPagePoolLowR3) < PAGE_SIZE, VERR_INTERNAL_ERROR);
68	int rc = SUPR3PageAllocEx(1, 0 /fFlags/, (void *)&pVM->mm.s.pPagePoolR3, NULL /pR0Ptr/, NULL /paPages*/);
69	if (RT_FAILURE(rc))
70	return rc;
71	memset(pVM->mm.s.pPagePoolR3, 0, PAGE_SIZE);
72	pVM->mm.s.pPagePoolR3->pVM = pVM;
73	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cPages, STAMTYPE_U32, "/MM/Page/Def/cPages", STAMUNIT_PAGES, "Number of pages in the default pool.");
74	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cFreePages, STAMTYPE_U32, "/MM/Page/Def/cFreePages", STAMUNIT_PAGES, "Number of free pages in the default pool.");
75	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cSubPools, STAMTYPE_U32, "/MM/Page/Def/cSubPools", STAMUNIT_COUNT, "Number of sub pools in the default pool.");
76	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cAllocCalls, STAMTYPE_COUNTER, "/MM/Page/Def/cAllocCalls", STAMUNIT_CALLS, "Number of MMR3PageAlloc() calls for the default pool.");
77	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cFreeCalls, STAMTYPE_COUNTER, "/MM/Page/Def/cFreeCalls", STAMUNIT_CALLS, "Number of MMR3PageFree()+MMR3PageFreeByPhys() calls for the default pool.");
78	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cToPhysCalls, STAMTYPE_COUNTER, "/MM/Page/Def/cToPhysCalls", STAMUNIT_CALLS, "Number of MMR3Page2Phys() calls for this pool.");
79	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cToVirtCalls, STAMTYPE_COUNTER, "/MM/Page/Def/cToVirtCalls", STAMUNIT_CALLS, "Number of MMR3PagePhys2Page()+MMR3PageFreeByPhys() calls for the default pool.");
80	STAM_REG(pVM, &pVM->mm.s.pPagePoolR3->cErrors, STAMTYPE_COUNTER, "/MM/Page/Def/cErrors", STAMUNIT_ERRORS,"Number of errors for the default pool.");
81
82	pVM->mm.s.pPagePoolLowR3 = pVM->mm.s.pPagePoolR3 + 1;
83	pVM->mm.s.pPagePoolLowR3->pVM = pVM;
84	pVM->mm.s.pPagePoolLowR3->fLow = true;
85	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cPages, STAMTYPE_U32, "/MM/Page/Low/cPages", STAMUNIT_PAGES, "Number of pages in the <4GB pool.");
86	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cFreePages, STAMTYPE_U32, "/MM/Page/Low/cFreePages", STAMUNIT_PAGES, "Number of free pages in the <4GB pool.");
87	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cSubPools, STAMTYPE_U32, "/MM/Page/Low/cSubPools", STAMUNIT_COUNT, "Number of sub pools in the <4GB pool.");
88	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cAllocCalls, STAMTYPE_COUNTER, "/MM/Page/Low/cAllocCalls", STAMUNIT_CALLS, "Number of MMR3PageAllocLow() calls for the <4GB pool.");
89	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cFreeCalls, STAMTYPE_COUNTER, "/MM/Page/Low/cFreeCalls", STAMUNIT_CALLS, "Number of MMR3PageFreeLow()+MMR3PageFreeByPhys() calls for the <4GB pool.");
90	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cToPhysCalls,STAMTYPE_COUNTER, "/MM/Page/Low/cToPhysCalls", STAMUNIT_CALLS, "Number of MMR3Page2Phys() calls for the <4GB pool.");
91	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cToVirtCalls,STAMTYPE_COUNTER, "/MM/Page/Low/cToVirtCalls", STAMUNIT_CALLS, "Number of MMR3PagePhys2Page()+MMR3PageFreeByPhys() calls for the <4GB pool.");
92	STAM_REG(pVM, &pVM->mm.s.pPagePoolLowR3->cErrors, STAMTYPE_COUNTER, "/MM/Page/Low/cErrors", STAMUNIT_ERRORS,"Number of errors for the <4GB pool.");
93
94	#ifndef VBOX_WITH_2X_4GB_ADDR_SPACE
95	pVM->mm.s.pPagePoolR0 = (uintptr_t)pVM->mm.s.pPagePoolR3;
96	pVM->mm.s.pPagePoolLowR0 = (uintptr_t)pVM->mm.s.pPagePoolLowR3;
97	#endif
98
99	/** @todo init a mutex? */
100	return VINF_SUCCESS;
101	}
102
103
104	/**
105	* Release all locks and free the allocated memory.
106	*
107	* @param pVM The cross context VM structure.
108	* @thread The Emulation Thread.
109	*/
110	void mmR3PagePoolTerm(PVM pVM)
111	{
112	if (pVM->mm.s.pPagePoolR3)
113	{
114	/*
115	* Unlock all memory held by subpools and free the memory.
116	* (The MM Heap will free the memory used for internal stuff.)
117	*/
118	Assert(!pVM->mm.s.pPagePoolR3->fLow);
119	PMMPAGESUBPOOL pSubPool = pVM->mm.s.pPagePoolR3->pHead;
120	while (pSubPool)
121	{
122	int rc = SUPR3PageFreeEx(pSubPool->pvPages, pSubPool->cPages);
123	AssertMsgRC(rc, ("SUPR3PageFreeEx(%p) failed with rc=%Rrc\n", pSubPool->pvPages, rc));
124	pSubPool->pvPages = NULL;
125
126	/* next */
127	pSubPool = pSubPool->pNext;
128	}
129	pVM->mm.s.pPagePoolR3 = NULL;
130	#ifndef VBOX_WITH_2X_4GB_ADDR_SPACE
131	pVM->mm.s.pPagePoolR0 = NIL_RTR0PTR;
132	#endif
133	}
134
135	if (pVM->mm.s.pPagePoolLowR3)
136	{
137	/*
138	* Free the memory.
139	*/
140	Assert(pVM->mm.s.pPagePoolLowR3->fLow);
141	PMMPAGESUBPOOL pSubPool = pVM->mm.s.pPagePoolLowR3->pHead;
142	while (pSubPool)
143	{
144	int rc = SUPR3LowFree(pSubPool->pvPages, pSubPool->cPages);
145	AssertMsgRC(rc, ("SUPR3LowFree(%p) failed with rc=%d\n", pSubPool->pvPages, rc));
146	pSubPool->pvPages = NULL;
147
148	/* next */
149	pSubPool = pSubPool->pNext;
150	}
151	pVM->mm.s.pPagePoolLowR3 = NULL;
152	#ifndef VBOX_WITH_2X_4GB_ADDR_SPACE
153	pVM->mm.s.pPagePoolLowR0 = NIL_RTR0PTR;
154	#endif
155	}
156	}
157
158
159	/**
160	* Allocates a page from the page pool.
161	*
162	* @returns Pointer to allocated page(s).
163	* @returns NULL on failure.
164	* @param pPool Pointer to the page pool.
165	* @thread The Emulation Thread.
166	*/
167	DECLINLINE(void *) mmR3PagePoolAlloc(PMMPAGEPOOL pPool)
168	{
169	VM_ASSERT_EMT(pPool->pVM);
170	STAM_COUNTER_INC(&pPool->cAllocCalls);
171
172	/*
173	* Walk free list.
174	*/
175	if (pPool->pHeadFree)
176	{
177	PMMPAGESUBPOOL pSub = pPool->pHeadFree;
178	/* decrement free count and unlink if no more free entries. */
179	if (!--pSub->cPagesFree)
180	pPool->pHeadFree = pSub->pNextFree;
181	#ifdef VBOX_WITH_STATISTICS
182	pPool->cFreePages--;
183	#endif
184
185	/* find free spot in bitmap. */
186	#ifdef USE_INLINE_ASM_BIT_OPS
187	const int iPage = ASMBitFirstClear(pSub->auBitmap, pSub->cPages);
188	if (iPage >= 0)
189	{
190	Assert(!ASMBitTest(pSub->auBitmap, iPage));
191	ASMBitSet(pSub->auBitmap, iPage);
192	return (uint8_t )pSub->pvPages + PAGE_SIZE iPage;
193	}
194	#else
195	unsigned *pu = &pSub->auBitmap[0];
196	unsigned puEnd = &pSub->auBitmap[pSub->cPages / (sizeof(pSub->auBitmap) 8)];
197	while (pu < puEnd)
198	{
199	unsigned u;
200	if ((u = *pu) != ~0U)
201	{
202	unsigned iBit = 0;
203	unsigned uMask = 1;
204	while (iBit < sizeof(pSub->auBitmap[0]) * 8)
205	{
206	if (!(u & uMask))
207	{
208	*pu \|= uMask;
209	return (uint8_t *)pSub->pvPages
210	+ PAGE_SIZE * (iBit + ((uint8_t )pu - (uint8_t )&pSub->auBitmap[0]) * 8);
211	}
212	iBit++;
213	uMask <<= 1;
214	}
215	STAM_COUNTER_INC(&pPool->cErrors);
216	AssertMsgFailed(("how odd, expected to find a free bit in %#x, but didn't\n", u));
217	}
218	/* next */
219	pu++;
220	}
221	#endif
222	STAM_COUNTER_INC(&pPool->cErrors);
223	#ifdef VBOX_WITH_STATISTICS
224	pPool->cFreePages++;
225	#endif
226	AssertMsgFailed(("how strange, expected to find a free bit in %p, but didn't (%d pages supposed to be free!)\n", pSub, pSub->cPagesFree + 1));
227	}
228
229	/*
230	* Allocate new subpool.
231	*/
232	unsigned cPages = !pPool->fLow ? 128 : 32;
233	PMMPAGESUBPOOL pSub;
234	int rc = MMHyperAlloc(pPool->pVM,
235	RT_OFFSETOF(MMPAGESUBPOOL, auBitmap[cPages / (sizeof(pSub->auBitmap[0]) * 8)])
236	+ (sizeof(SUPPAGE) + sizeof(MMPPLOOKUPHCPHYS)) * cPages
237	+ sizeof(MMPPLOOKUPHCPTR),
238	0,
239	MM_TAG_MM_PAGE,
240	(void **)&pSub);
241	if (RT_FAILURE(rc))
242	return NULL;
243
244	PSUPPAGE paPhysPages = (PSUPPAGE)&pSub->auBitmap[cPages / (sizeof(pSub->auBitmap[0]) * 8)];
245	Assert((uintptr_t)paPhysPages >= (uintptr_t)&pSub->auBitmap[1]);
246	if (!pPool->fLow)
247	{
248	rc = SUPR3PageAllocEx(cPages,
249	0 /* fFlags */,
250	&pSub->pvPages,
251	NULL,
252	paPhysPages);
253	if (RT_FAILURE(rc))
254	rc = VMSetError(pPool->pVM, rc, RT_SRC_POS,
255	N_("Failed to lock host %zd bytes of memory (out of memory)"), (size_t)cPages << PAGE_SHIFT);
256	}
257	else
258	rc = SUPR3LowAlloc(cPages, &pSub->pvPages, NULL, paPhysPages);
259	if (RT_SUCCESS(rc))
260	{
261	/*
262	* Setup the sub structure and allocate the requested page.
263	*/
264	pSub->cPages = cPages;
265	pSub->cPagesFree= cPages - 1;
266	pSub->paPhysPages = paPhysPages;
267	memset(pSub->auBitmap, 0, cPages / 8);
268	/* allocate first page. */
269	pSub->auBitmap[0] \|= 1;
270	/* link into free chain. */
271	pSub->pNextFree = pPool->pHeadFree;
272	pPool->pHeadFree= pSub;
273	/* link into main chain. */
274	pSub->pNext = pPool->pHead;
275	pPool->pHead = pSub;
276	/* update pool statistics. */
277	pPool->cSubPools++;
278	pPool->cPages += cPages;
279	#ifdef VBOX_WITH_STATISTICS
280	pPool->cFreePages += cPages - 1;
281	#endif
282
283	/*
284	* Initialize the physical pages with backpointer to subpool.
285	*/
286	unsigned i = cPages;
287	while (i-- > 0)
288	{
289	AssertMsg(paPhysPages[i].Phys && !(paPhysPages[i].Phys & PAGE_OFFSET_MASK),
290	("i=%d Phys=%d\n", i, paPhysPages[i].Phys));
291	paPhysPages[i].uReserved = (RTHCUINTPTR)pSub;
292	}
293
294	/*
295	* Initialize the physical lookup record with backpointers to the physical pages.
296	*/
297	PMMPPLOOKUPHCPHYS paLookupPhys = (PMMPPLOOKUPHCPHYS)&paPhysPages[cPages];
298	i = cPages;
299	while (i-- > 0)
300	{
301	paLookupPhys[i].pPhysPage = &paPhysPages[i];
302	paLookupPhys[i].Core.Key = paPhysPages[i].Phys;
303	RTAvlHCPhysInsert(&pPool->pLookupPhys, &paLookupPhys[i].Core);
304	}
305
306	/*
307	* And the one record for virtual memory lookup.
308	*/
309	PMMPPLOOKUPHCPTR pLookupVirt = (PMMPPLOOKUPHCPTR)&paLookupPhys[cPages];
310	pLookupVirt->pSubPool = pSub;
311	pLookupVirt->Core.Key = pSub->pvPages;
312	RTAvlPVInsert(&pPool->pLookupVirt, &pLookupVirt->Core);
313
314	/* return allocated page (first). */
315	return pSub->pvPages;
316	}
317
318	MMHyperFree(pPool->pVM, pSub);
319	STAM_COUNTER_INC(&pPool->cErrors);
320	if (pPool->fLow)
321	VMSetError(pPool->pVM, rc, RT_SRC_POS,
322	N_("Failed to expand page pool for memory below 4GB. Current size: %d pages"),
323	pPool->cPages);
324	AssertMsgFailed(("Failed to expand pool%s. rc=%Rrc poolsize=%d\n",
325	pPool->fLow ? " (<4GB)" : "", rc, pPool->cPages));
326	return NULL;
327	}
328
329
330	/**
331	* Frees a page from the page pool.
332	*
333	* @param pPool Pointer to the page pool.
334	* @param pv Pointer to the page to free.
335	* I.e. pointer returned by mmR3PagePoolAlloc().
336	* @thread The Emulation Thread.
337	*/
338	DECLINLINE(void) mmR3PagePoolFree(PMMPAGEPOOL pPool, void *pv)
339	{
340	VM_ASSERT_EMT(pPool->pVM);
341	STAM_COUNTER_INC(&pPool->cFreeCalls);
342
343	/*
344	* Lookup the virtual address.
345	*/
346	PMMPPLOOKUPHCPTR pLookup = (PMMPPLOOKUPHCPTR)RTAvlPVGetBestFit(&pPool->pLookupVirt, pv, false);
347	if ( !pLookup
348	\|\| (uint8_t )pv >= (uint8_t )pLookup->pSubPool->pvPages + (pLookup->pSubPool->cPages << PAGE_SHIFT)
349	)
350	{
351	STAM_COUNTER_INC(&pPool->cErrors);
352	AssertMsgFailed(("invalid pointer %p\n", pv));
353	return;
354	}
355
356	/*
357	* Free the page.
358	*/
359	PMMPAGESUBPOOL pSubPool = pLookup->pSubPool;
360	/* clear bitmap bit */
361	const unsigned iPage = ((uint8_t )pv - (uint8_t )pSubPool->pvPages) >> PAGE_SHIFT;
362	#ifdef USE_INLINE_ASM_BIT_OPS
363	Assert(ASMBitTest(pSubPool->auBitmap, iPage));
364	ASMBitClear(pSubPool->auBitmap, iPage);
365	#else
366	unsigned iBit = iPage % (sizeof(pSubPool->auBitmap[0]) * 8);
367	unsigned iIndex = iPage / (sizeof(pSubPool->auBitmap[0]) * 8);
368	pSubPool->auBitmap[iIndex] &= ~(1 << iBit);
369	#endif
370	/* update stats. */
371	pSubPool->cPagesFree++;
372	#ifdef VBOX_WITH_STATISTICS
373	pPool->cFreePages++;
374	#endif
375	if (pSubPool->cPagesFree == 1)
376	{
377	pSubPool->pNextFree = pPool->pHeadFree;
378	pPool->pHeadFree = pSubPool;
379	}
380	}
381
382
383	/**
384	* Allocates a page from the page pool.
385	*
386	* This function may returns pages which has physical addresses any
387	* where. If you require a page to be within the first 4GB of physical
388	* memory, use MMR3PageAllocLow().
389	*
390	* @returns Pointer to the allocated page page.
391	* @returns NULL on failure.
392	* @param pVM The cross context VM structure.
393	* @thread The Emulation Thread.
394	*/
395	VMMR3DECL(void *) MMR3PageAlloc(PVM pVM)
396	{
397	/* Note: unprotected by locks; currently fine as it's used during init or under the PGM lock */
398	return mmR3PagePoolAlloc(pVM->mm.s.pPagePoolR3);
399	}
400
401
402	/**
403	* Allocates a page from the page pool and return its physical address.
404	*
405	* This function may returns pages which has physical addresses any
406	* where. If you require a page to be within the first 4GB of physical
407	* memory, use MMR3PageAllocLow().
408	*
409	* @returns Pointer to the allocated page page.
410	* @returns NIL_RTHCPHYS on failure.
411	* @param pVM The cross context VM structure.
412	* @thread The Emulation Thread.
413	*/
414	VMMR3DECL(RTHCPHYS) MMR3PageAllocPhys(PVM pVM)
415	{
416	/* Note: unprotected by locks; currently fine as it's used during init or under the PGM lock */
417	/** @todo optimize this, it's the most common case now. */
418	void *pv = mmR3PagePoolAlloc(pVM->mm.s.pPagePoolR3);
419	if (pv)
420	return mmPagePoolPtr2Phys(pVM->mm.s.pPagePoolR3, pv);
421	return NIL_RTHCPHYS;
422	}
423
424
425	/**
426	* Frees a page allocated from the page pool by MMR3PageAlloc() or
427	* MMR3PageAllocPhys().
428	*
429	* @param pVM The cross context VM structure.
430	* @param pvPage Pointer to the page.
431	* @thread The Emulation Thread.
432	*/
433	VMMR3DECL(void) MMR3PageFree(PVM pVM, void *pvPage)
434	{
435	mmR3PagePoolFree(pVM->mm.s.pPagePoolR3, pvPage);
436	}
437
438
439	/**
440	* Allocates a page from the low page pool.
441	*
442	* @returns Pointer to the allocated page.
443	* @returns NULL on failure.
444	* @param pVM The cross context VM structure.
445	* @thread The Emulation Thread.
446	*/
447	VMMR3DECL(void *) MMR3PageAllocLow(PVM pVM)
448	{
449	return mmR3PagePoolAlloc(pVM->mm.s.pPagePoolLowR3);
450	}
451
452
453	/**
454	* Frees a page allocated from the page pool by MMR3PageAllocLow().
455	*
456	* @param pVM The cross context VM structure.
457	* @param pvPage Pointer to the page.
458	* @thread The Emulation Thread.
459	*/
460	VMMR3DECL(void) MMR3PageFreeLow(PVM pVM, void *pvPage)
461	{
462	mmR3PagePoolFree(pVM->mm.s.pPagePoolLowR3, pvPage);
463	}
464
465
466	/**
467	* Free a page allocated from the page pool by physical address.
468	* This works for pages allocated by MMR3PageAlloc(), MMR3PageAllocPhys()
469	* and MMR3PageAllocLow().
470	*
471	* @param pVM The cross context VM structure.
472	* @param HCPhysPage The physical address of the page to be freed.
473	* @thread The Emulation Thread.
474	*/
475	VMMR3DECL(void) MMR3PageFreeByPhys(PVM pVM, RTHCPHYS HCPhysPage)
476	{
477	void *pvPage = mmPagePoolPhys2Ptr(pVM->mm.s.pPagePoolR3, HCPhysPage);
478	if (!pvPage)
479	pvPage = mmPagePoolPhys2Ptr(pVM->mm.s.pPagePoolLowR3, HCPhysPage);
480	if (pvPage)
481	mmR3PagePoolFree(pVM->mm.s.pPagePoolR3, pvPage);
482	else
483	AssertMsgFailed(("Invalid address HCPhysPT=%#x\n", HCPhysPage));
484	}
485
486
487	/**
488	* Gets the HC pointer to the dummy page.
489	*
490	* The dummy page is used as a place holder to prevent potential bugs
491	* from doing really bad things to the system.
492	*
493	* @returns Pointer to the dummy page.
494	* @param pVM The cross context VM structure.
495	* @thread The Emulation Thread.
496	*/
497	VMMR3DECL(void *) MMR3PageDummyHCPtr(PVM pVM)
498	{
499	VM_ASSERT_EMT(pVM);
500	if (!pVM->mm.s.pvDummyPage)
501	{
502	pVM->mm.s.pvDummyPage = mmR3PagePoolAlloc(pVM->mm.s.pPagePoolR3);
503	AssertRelease(pVM->mm.s.pvDummyPage);
504	pVM->mm.s.HCPhysDummyPage = mmPagePoolPtr2Phys(pVM->mm.s.pPagePoolR3, pVM->mm.s.pvDummyPage);
505	AssertRelease(!(pVM->mm.s.HCPhysDummyPage & ~X86_PTE_PAE_PG_MASK));
506	}
507	return pVM->mm.s.pvDummyPage;
508	}
509
510
511	/**
512	* Gets the HC Phys to the dummy page.
513	*
514	* The dummy page is used as a place holder to prevent potential bugs
515	* from doing really bad things to the system.
516	*
517	* @returns Pointer to the dummy page.
518	* @param pVM The cross context VM structure.
519	* @thread The Emulation Thread.
520	*/
521	VMMR3DECL(RTHCPHYS) MMR3PageDummyHCPhys(PVM pVM)
522	{
523	VM_ASSERT_EMT(pVM);
524	if (!pVM->mm.s.pvDummyPage)
525	MMR3PageDummyHCPtr(pVM);
526	return pVM->mm.s.HCPhysDummyPage;
527	}
528

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source: vbox/trunk/src/VBox/VMM/VMMR3/MMPagePool.cpp@ 61794

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