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(MigrationIncomingState *mis);
  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  * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
  39  * however leaving it until after precopy means that most of the precopy
  40  * data is still THPd
  41  */
  42 int postcopy_ram_prepare_discard(MigrationIncomingState *mis);
  43
  44 /*
  45  * Called at the start of each RAMBlock by the bitmap code.
  46  * Returns a new PDS
  47  */
  48 PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
  49                                                  const char *name);
  50
  51 /*
  52  * Called by the bitmap code for each chunk to discard.
  53  * May send a discard message, may just leave it queued to
  54  * be sent later.
  55  * @start,@length: a range of pages in the migration bitmap in the
  56  *  RAM block passed to postcopy_discard_send_init() (length=1 is one page)
  57  */
  58 void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds,
  59                                  unsigned long start, unsigned long length);
  60
  61 /*
  62  * Called at the end of each RAMBlock by the bitmap code.
  63  * Sends any outstanding discard messages, frees the PDS.
  64  */
  65 void postcopy_discard_send_finish(MigrationState *ms,
  66                                   PostcopyDiscardState *pds);
  67
  68 /*
  69  * Place a page (from) at (host) efficiently
  70  *    There are restrictions on how 'from' must be mapped, in general best
  71  *    to use other postcopy_ routines to allocate.
  72  * returns 0 on success
  73  */
  74 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
  75                         RAMBlock *rb);
  76
  77 /*
  78  * Place a zero page at (host) atomically
  79  * returns 0 on success
  80  */
  81 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
  82                              RAMBlock *rb);
  83
  84 /* The current postcopy state is read/set by postcopy_state_get/set
  85  * which update it atomically.
  86  * The state is updated as postcopy messages are received, and
  87  * in general only one thread should be writing to the state at any one
  88  * time, initially the main thread and then the listen thread;
  89  * Corner cases are where either thread finishes early and/or errors.
  90  * The state is checked as messages are received to ensure that
  91  * the source is sending us messages in the correct order.
  92  * The state is also used by the RAM reception code to know if it
  93  * has to place pages atomically, and the cleanup code at the end of
  94  * the main thread to know if it has to delay cleanup until the end
  95  * of postcopy.
  96  */
  97 typedef enum {
  98     POSTCOPY_INCOMING_NONE = 0,  /* Initial state - no postcopy */
  99     POSTCOPY_INCOMING_ADVISE,
 100     POSTCOPY_INCOMING_DISCARD,
 101     POSTCOPY_INCOMING_LISTENING,
 102     POSTCOPY_INCOMING_RUNNING,
 103     POSTCOPY_INCOMING_END
 104 } PostcopyState;
 105
 106 /*
 107  * Allocate a page of memory that can be mapped at a later point in time
 108  * using postcopy_place_page
 109  * Returns: Pointer to allocated page
 110  */
 111 void *postcopy_get_tmp_page(MigrationIncomingState *mis);
 112
 113 PostcopyState postcopy_state_get(void);
 114 /* Set the state and return the old state */
 115 PostcopyState postcopy_state_set(PostcopyState new_state);
 116
 117 #endif