include/migration/postcopy-ram.h

   1 /*
   2  * Postcopy migration for RAM
   3  *
   4  * Copyright 2013 Red Hat, Inc. and/or its affiliates
   5  *
   6  * Authors:
   7  *  Dave Gilbert  <dgilbert@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  */
  13 #ifndef QEMU_POSTCOPY_RAM_H
  14 #define QEMU_POSTCOPY_RAM_H
  15
  16 /* Return true if the host supports everything we need to do postcopy-ram */
  17 bool postcopy_ram_supported_by_host(void);
  18
  19 /*
  20  * Make all of RAM sensitive to accesses to areas that haven't yet been written
  21  * and wire up anything necessary to deal with it.
  22  */
  23 int postcopy_ram_enable_notify(MigrationIncomingState *mis);
  24
  25 /*
  26  * Initialise postcopy-ram, setting the RAM to a state where we can go into
  27  * postcopy later; must be called prior to any precopy.
  28  * called from ram.c's similarly named ram_postcopy_incoming_init
  29  */
  30 int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages);
  31
  32 /*
  33  * At the end of a migration where postcopy_ram_incoming_init was called.
  34  */
  35 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
  36
  37 /*
  38  * Discard the contents of 'length' bytes from 'start'
  39  * We can assume that if we've been called postcopy_ram_hosttest returned true
  40  */
  41 int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
  42                                size_t length);
  43
  44 /*
  45  * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
  46  * however leaving it until after precopy means that most of the precopy
  47  * data is still THPd
  48  */
  49 int postcopy_ram_prepare_discard(MigrationIncomingState *mis);
  50
  51 /*
  52  * Called at the start of each RAMBlock by the bitmap code.
  53  * 'offset' is the bitmap offset of the named RAMBlock in the migration
  54  * bitmap.
  55  * Returns a new PDS
  56  */
  57 PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
  58                                                  unsigned long offset,
  59                                                  const char *name);
  60
  61 /*
  62  * Called by the bitmap code for each chunk to discard.
  63  * May send a discard message, may just leave it queued to
  64  * be sent later.
  65  * @start,@length: a range of pages in the migration bitmap in the
  66  *  RAM block passed to postcopy_discard_send_init() (length=1 is one page)
  67  */
  68 void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds,
  69                                  unsigned long start, unsigned long length);
  70
  71 /*
  72  * Called at the end of each RAMBlock by the bitmap code.
  73  * Sends any outstanding discard messages, frees the PDS.
  74  */
  75 void postcopy_discard_send_finish(MigrationState *ms,
  76                                   PostcopyDiscardState *pds);
  77
  78 /*
  79  * Place a page (from) at (host) efficiently
  80  *    There are restrictions on how 'from' must be mapped, in general best
  81  *    to use other postcopy_ routines to allocate.
  82  * returns 0 on success
  83  */
  84 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from);
  85
  86 /*
  87  * Place a zero page at (host) atomically
  88  * returns 0 on success
  89  */
  90 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host);
  91
  92 /*
  93  * Allocate a page of memory that can be mapped at a later point in time
  94  * using postcopy_place_page
  95  * Returns: Pointer to allocated page
  96  */
  97 void *postcopy_get_tmp_page(MigrationIncomingState *mis);
  98
  99 #endif