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);
  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  */
  47 void postcopy_discard_send_init(MigrationState *ms, const char *name);
  48
  49 /*
  50  * Called by the bitmap code for each chunk to discard.
  51  * May send a discard message, may just leave it queued to
  52  * be sent later.
  53  * @start,@length: a range of pages in the migration bitmap in the
  54  *  RAM block passed to postcopy_discard_send_init() (length=1 is one page)
  55  */
  56 void postcopy_discard_send_range(MigrationState *ms, unsigned long start,
  57                                  unsigned long length);
  58
  59 /*
  60  * Called at the end of each RAMBlock by the bitmap code.
  61  * Sends any outstanding discard messages.
  62  */
  63 void postcopy_discard_send_finish(MigrationState *ms);
  64
  65 /*
  66  * Place a page (from) at (host) efficiently
  67  *    There are restrictions on how 'from' must be mapped, in general best
  68  *    to use other postcopy_ routines to allocate.
  69  * returns 0 on success
  70  */
  71 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
  72                         RAMBlock *rb);
  73
  74 /*
  75  * Place a zero page at (host) atomically
  76  * returns 0 on success
  77  */
  78 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
  79                              RAMBlock *rb);
  80
  81 /* The current postcopy state is read/set by postcopy_state_get/set
  82  * which update it atomically.
  83  * The state is updated as postcopy messages are received, and
  84  * in general only one thread should be writing to the state at any one
  85  * time, initially the main thread and then the listen thread;
  86  * Corner cases are where either thread finishes early and/or errors.
  87  * The state is checked as messages are received to ensure that
  88  * the source is sending us messages in the correct order.
  89  * The state is also used by the RAM reception code to know if it
  90  * has to place pages atomically, and the cleanup code at the end of
  91  * the main thread to know if it has to delay cleanup until the end
  92  * of postcopy.
  93  */
  94 typedef enum {
  95     POSTCOPY_INCOMING_NONE = 0,  /* Initial state - no postcopy */
  96     POSTCOPY_INCOMING_ADVISE,
  97     POSTCOPY_INCOMING_DISCARD,
  98     POSTCOPY_INCOMING_LISTENING,
  99     POSTCOPY_INCOMING_RUNNING,
 100     POSTCOPY_INCOMING_END
 101 } PostcopyState;
 102
 103 /*
 104  * Allocate a page of memory that can be mapped at a later point in time
 105  * using postcopy_place_page
 106  * Returns: Pointer to allocated page
 107  */
 108 void *postcopy_get_tmp_page(MigrationIncomingState *mis);
 109
 110 PostcopyState postcopy_state_get(void);
 111 /* Set the state and return the old state */
 112 PostcopyState postcopy_state_set(PostcopyState new_state);
 113
 114 void postcopy_fault_thread_notify(MigrationIncomingState *mis);
 115
 116 /*
 117  * To be called once at the start before any device initialisation
 118  */
 119 void postcopy_infrastructure_init(void);
 120
 121 /* Add a notifier to a list to be called when checking whether the devices
 122  * can support postcopy.
 123  * It's data is a *PostcopyNotifyData
 124  * It should return 0 if OK, or a negative value on failure.
 125  * On failure it must set the data->errp to an error.
 126  *
 127  */
 128 enum PostcopyNotifyReason {
 129     POSTCOPY_NOTIFY_PROBE = 0,
 130     POSTCOPY_NOTIFY_INBOUND_ADVISE,
 131     POSTCOPY_NOTIFY_INBOUND_LISTEN,
 132     POSTCOPY_NOTIFY_INBOUND_END,
 133 };
 134
 135 struct PostcopyNotifyData {
 136     enum PostcopyNotifyReason reason;
 137     Error **errp;
 138 };
 139
 140 void postcopy_add_notifier(NotifierWithReturn *nn);
 141 void postcopy_remove_notifier(NotifierWithReturn *n);
 142 /* Call the notifier list set by postcopy_add_start_notifier */
 143 int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp);
 144
 145 struct PostCopyFD;
 146
 147 /* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */
 148 typedef int (*pcfdhandler)(struct PostCopyFD *pcfd, void *ufd);
 149 /* Notification to wake, either on place or on reception of
 150  * a fault on something that's already arrived (race)
 151  */
 152 typedef int (*pcfdwake)(struct PostCopyFD *pcfd, RAMBlock *rb, uint64_t offset);
 153
 154 struct PostCopyFD {
 155     int fd;
 156     /* Data to pass to handler */
 157     void *data;
 158     /* Handler to be called whenever we get a poll event */
 159     pcfdhandler handler;
 160     /* Notification to wake shared client */
 161     pcfdwake waker;
 162     /* A string to use in error messages */
 163     const char *idstr;
 164 };
 165
 166 /* Register a userfaultfd owned by an external process for
 167  * shared memory.
 168  */
 169 void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
 170 void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
 171 /* Call each of the shared 'waker's registerd telling them of
 172  * availability of a block.
 173  */
 174 int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset);
 175 /* postcopy_wake_shared: Notify a client ufd that a page is available
 176  *
 177  * Returns 0 on success
 178  *
 179  * @pcfd: Structure with fd, handler and name as above
 180  * @client_addr: Address in the client program, not QEMU
 181  * @rb: The RAMBlock the page is in
 182  */
 183 int postcopy_wake_shared(struct PostCopyFD *pcfd, uint64_t client_addr,
 184                          RAMBlock *rb);
 185 /* Callback from shared fault handlers to ask for a page */
 186 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
 187                                  uint64_t client_addr, uint64_t offset);
 188
 189 #endif