blob: d900d9c34fdc24865b0a2de38cd08b59394fe18a [file] [log] [blame]
* Postcopy migration for RAM
* Copyright 2013 Red Hat, Inc. and/or its affiliates
* Authors:
* Dave Gilbert <>
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
/* Return true if the host supports everything we need to do postcopy-ram */
bool postcopy_ram_supported_by_host(MigrationIncomingState *mis);
* Make all of RAM sensitive to accesses to areas that haven't yet been written
* and wire up anything necessary to deal with it.
int postcopy_ram_enable_notify(MigrationIncomingState *mis);
* Initialise postcopy-ram, setting the RAM to a state where we can go into
* postcopy later; must be called prior to any precopy.
* called from ram.c's similarly named ram_postcopy_incoming_init
int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages);
* At the end of a migration where postcopy_ram_incoming_init was called.
int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
* Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
* however leaving it until after precopy means that most of the precopy
* data is still THPd
int postcopy_ram_prepare_discard(MigrationIncomingState *mis);
* Called at the start of each RAMBlock by the bitmap code.
* Returns a new PDS
PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
const char *name);
* Called by the bitmap code for each chunk to discard.
* May send a discard message, may just leave it queued to
* be sent later.
* @start,@length: a range of pages in the migration bitmap in the
* RAM block passed to postcopy_discard_send_init() (length=1 is one page)
void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds,
unsigned long start, unsigned long length);
* Called at the end of each RAMBlock by the bitmap code.
* Sends any outstanding discard messages, frees the PDS.
void postcopy_discard_send_finish(MigrationState *ms,
PostcopyDiscardState *pds);
* Place a page (from) at (host) efficiently
* There are restrictions on how 'from' must be mapped, in general best
* to use other postcopy_ routines to allocate.
* returns 0 on success
int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
RAMBlock *rb);
* Place a zero page at (host) atomically
* returns 0 on success
int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
RAMBlock *rb);
/* The current postcopy state is read/set by postcopy_state_get/set
* which update it atomically.
* The state is updated as postcopy messages are received, and
* in general only one thread should be writing to the state at any one
* time, initially the main thread and then the listen thread;
* Corner cases are where either thread finishes early and/or errors.
* The state is checked as messages are received to ensure that
* the source is sending us messages in the correct order.
* The state is also used by the RAM reception code to know if it
* has to place pages atomically, and the cleanup code at the end of
* the main thread to know if it has to delay cleanup until the end
* of postcopy.
typedef enum {
POSTCOPY_INCOMING_NONE = 0, /* Initial state - no postcopy */
} PostcopyState;
* Allocate a page of memory that can be mapped at a later point in time
* using postcopy_place_page
* Returns: Pointer to allocated page
void *postcopy_get_tmp_page(MigrationIncomingState *mis);
PostcopyState postcopy_state_get(void);
/* Set the state and return the old state */
PostcopyState postcopy_state_set(PostcopyState new_state);
void postcopy_fault_thread_notify(MigrationIncomingState *mis);
* To be called once at the start before any device initialisation
void postcopy_infrastructure_init(void);
/* Add a notifier to a list to be called when checking whether the devices
* can support postcopy.
* It's data is a *PostcopyNotifyData
* It should return 0 if OK, or a negative value on failure.
* On failure it must set the data->errp to an error.
enum PostcopyNotifyReason {
struct PostcopyNotifyData {
enum PostcopyNotifyReason reason;
Error **errp;
void postcopy_add_notifier(NotifierWithReturn *nn);
void postcopy_remove_notifier(NotifierWithReturn *n);
/* Call the notifier list set by postcopy_add_start_notifier */
int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp);
struct PostCopyFD;
/* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */
typedef int (*pcfdhandler)(struct PostCopyFD *pcfd, void *ufd);
/* Notification to wake, either on place or on reception of
* a fault on something that's already arrived (race)
typedef int (*pcfdwake)(struct PostCopyFD *pcfd, RAMBlock *rb, uint64_t offset);
struct PostCopyFD {
int fd;
/* Data to pass to handler */
void *data;
/* Handler to be called whenever we get a poll event */
pcfdhandler handler;
/* Notification to wake shared client */
pcfdwake waker;
/* A string to use in error messages */
const char *idstr;
/* Register a userfaultfd owned by an external process for
* shared memory.
void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
/* Call each of the shared 'waker's registerd telling them of
* availability of a block.
int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset);
/* postcopy_wake_shared: Notify a client ufd that a page is available
* Returns 0 on success
* @pcfd: Structure with fd, handler and name as above
* @client_addr: Address in the client program, not QEMU
* @rb: The RAMBlock the page is in
int postcopy_wake_shared(struct PostCopyFD *pcfd, uint64_t client_addr,
RAMBlock *rb);
/* Callback from shared fault handlers to ask for a page */
int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
uint64_t client_addr, uint64_t offset);