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 void postcopy_fault_thread_notify(MigrationIncomingState *mis);
 118
 119 /*
 120  * To be called once at the start before any device initialisation
 121  */
 122 void postcopy_infrastructure_init(void);
 123
 124 /* Add a notifier to a list to be called when checking whether the devices
 125  * can support postcopy.
 126  * It's data is a *PostcopyNotifyData
 127  * It should return 0 if OK, or a negative value on failure.
 128  * On failure it must set the data->errp to an error.
 129  *
 130  */
 131 enum PostcopyNotifyReason {
 132     POSTCOPY_NOTIFY_PROBE = 0,
 133     POSTCOPY_NOTIFY_INBOUND_ADVISE,
 134     POSTCOPY_NOTIFY_INBOUND_LISTEN,
 135     POSTCOPY_NOTIFY_INBOUND_END,
 136 };
 137
 138 struct PostcopyNotifyData {
 139     enum PostcopyNotifyReason reason;
 140     Error **errp;
 141 };
 142
 143 void postcopy_add_notifier(NotifierWithReturn *nn);
 144 void postcopy_remove_notifier(NotifierWithReturn *n);
 145 /* Call the notifier list set by postcopy_add_start_notifier */
 146 int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp);
 147
 148 struct PostCopyFD;
 149
 150 /* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */
 151 typedef int (*pcfdhandler)(struct PostCopyFD *pcfd, void *ufd);
 152 /* Notification to wake, either on place or on reception of
 153  * a fault on something that's already arrived (race)
 154  */
 155 typedef int (*pcfdwake)(struct PostCopyFD *pcfd, RAMBlock *rb, uint64_t offset);
 156
 157 struct PostCopyFD {
 158     int fd;
 159     /* Data to pass to handler */
 160     void *data;
 161     /* Handler to be called whenever we get a poll event */
 162     pcfdhandler handler;
 163     /* Notification to wake shared client */
 164     pcfdwake waker;
 165     /* A string to use in error messages */
 166     const char *idstr;
 167 };
 168
 169 /* Register a userfaultfd owned by an external process for
 170  * shared memory.
 171  */
 172 void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
 173 void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
 174 /* Call each of the shared 'waker's registerd telling them of
 175  * availability of a block.
 176  */
 177 int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset);
 178 /* postcopy_wake_shared: Notify a client ufd that a page is available
 179  *
 180  * Returns 0 on success
 181  *
 182  * @pcfd: Structure with fd, handler and name as above
 183  * @client_addr: Address in the client program, not QEMU
 184  * @rb: The RAMBlock the page is in
 185  */
 186 int postcopy_wake_shared(struct PostCopyFD *pcfd, uint64_t client_addr,
 187                          RAMBlock *rb);
 188 /* Callback from shared fault handlers to ask for a page */
 189 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
 190                                  uint64_t client_addr, uint64_t offset);
 191
 192 #endif