Re: [Qemu-devel] [PATCH v0 4/7] migration: add background snapshot infrastructure

[Dr. David Alan Gilbert]

* Denis Plotnikov (address@hidden) wrote:
> It allows to intercept VM's RAM access and write them into the
> snapshot.

This is too big for me to properly review; it needs splitting
into smaller chunks.
However, there are some comments below.

> Signed-off-by: Denis Plotnikov <address@hidden>
> ---
>  include/exec/ram_addr.h |   7 +
>  include/exec/ramlist.h  |   4 +-
>  migration/migration.c   |   2 +-
>  migration/ram.c         | 333 ++++++++++++++++++++++++++++++++++++++--
>  migration/ram.h         |  11 +-
>  5 files changed, 338 insertions(+), 19 deletions(-)
> 
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 6cbc02aa0f..5b403d537d 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -36,6 +36,8 @@ struct RAMBlock {
>      char idstr[256];
>      /* RCU-enabled, writes protected by the ramlist lock */
>      QLIST_ENTRY(RAMBlock) next;
> +    /* blocks used for background snapshot */
> +    QLIST_ENTRY(RAMBlock) bgs_next;
>      QLIST_HEAD(, RAMBlockNotifier) ramblock_notifiers;
>      int fd;
>      size_t page_size;
> @@ -49,6 +51,11 @@ struct RAMBlock {
>      unsigned long *unsentmap;
>      /* bitmap of already received pages in postcopy */
>      unsigned long *receivedmap;
> +    /* The following 2 are for background snapshot */
> +    /* Pages currently being copied */
> +    unsigned long *touched_map;
> +    /* Pages has been copied already */
> +    unsigned long *copied_map;

Does this need to touch exec/ram_addr.h or can we keep this
all private to the migration code?

>  };
>  
>  static inline bool offset_in_ramblock(RAMBlock *b, ram_addr_t offset)
> diff --git a/include/exec/ramlist.h b/include/exec/ramlist.h
> index 2e2ac6cb99..e0231d3bec 100644
> --- a/include/exec/ramlist.h
> +++ b/include/exec/ramlist.h
> @@ -44,11 +44,13 @@ typedef struct {
>      unsigned long *blocks[];
>  } DirtyMemoryBlocks;
>  
> +typedef QLIST_HEAD(, RAMBlock) RamBlockList;
> +
>  typedef struct RAMList {
>      QemuMutex mutex;
>      RAMBlock *mru_block;
>      /* RCU-enabled, writes protected by the ramlist lock. */
> -    QLIST_HEAD(, RAMBlock) blocks;
> +    RamBlockList blocks;
>      DirtyMemoryBlocks *dirty_memory[DIRTY_MEMORY_NUM];
>      uint32_t version;
>      QLIST_HEAD(, RAMBlockNotifier) ramblock_notifiers;
> diff --git a/migration/migration.c b/migration/migration.c
> index 87096d23ef..131d0904e4 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1716,7 +1716,7 @@ static void migrate_handle_rp_req_pages(MigrationState 
> *ms, const char* rbname,
>          return;
>      }
>  
> -    if (ram_save_queue_pages(rbname, start, len)) {
> +    if (ram_save_queue_pages(NULL, rbname, start, len, NULL)) {
>          mark_source_rp_bad(ms);
>      }
>  }
> diff --git a/migration/ram.c b/migration/ram.c
> index 021d583b9b..286b79ad51 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -188,10 +188,21 @@ struct RAMSrcPageRequest {
>      RAMBlock *rb;
>      hwaddr    offset;
>      hwaddr    len;
> +    void*     page_copy;
>  
>      QSIMPLEQ_ENTRY(RAMSrcPageRequest) next_req;
>  };
>  
> +/* Page buffer used for background snapshot */
> +typedef struct RAMPageBuffer {
> +    /* Page buffer capacity in host pages */
> +    int capacity;
> +    /* Current number of pages in the buffer */
> +    int used;
> +    /* Event to notify that buffer usage is under capacity */
> +    QemuEvent used_decreased;
> +} RAMPageBuffer;
> +
>  /* State of RAM for migration */
>  struct RAMState {
>      /* QEMUFile used for this migration */
> @@ -230,6 +241,11 @@ struct RAMState {
>      /* Queue of outstanding page requests from the destination */
>      QemuMutex src_page_req_mutex;
>      QSIMPLEQ_HEAD(src_page_requests, RAMSrcPageRequest) src_page_requests;
> +    /* The following 2 are for background snapshot */
> +    /* Buffer data to store copies of ram pages while async vm saving */
> +    RAMPageBuffer page_buffer;
> +    /* Event to notify that a page coping just has finished*/
> +    QemuEvent page_coping_done;

typo: copin->copying (you've got that in a few places)

>  };
>  typedef struct RAMState RAMState;
>  
> @@ -250,6 +266,8 @@ struct PageSearchStatus {
>      unsigned long page;
>      /* Set once we wrap around */
>      bool         complete_round;
> +    /* Pointer to the cached page */
> +    void* page_copy;
>  };
>  typedef struct PageSearchStatus PageSearchStatus;
>  
> @@ -958,7 +976,11 @@ static int ram_save_page(RAMState *rs, PageSearchStatus 
> *pss, bool last_stage)
>      RAMBlock *block = pss->block;
>      ram_addr_t offset = pss->page << TARGET_PAGE_BITS;
>  
> -    p = block->host + offset;
> +    if (pss->page_copy) {
> +        p = pss->page_copy;
> +    } else {
> +        p = block->host + offset;
> +    }
>      trace_ram_save_page(block->idstr, (uint64_t)offset, p);
>  
>      /* In doubt sent page as normal */
> @@ -989,9 +1011,12 @@ static int ram_save_page(RAMState *rs, PageSearchStatus 
> *pss, bool last_stage)
>               * page would be stale
>               */
>              xbzrle_cache_zero_page(rs, current_addr);
> -            ram_release_pages(block->idstr, offset, pages);
> +            if (pss->page_copy) {
> +                qemu_madvise(p, TARGET_PAGE_SIZE, MADV_DONTNEED);
> +            }

Is it easier/better just to change the logic in ram_release_pages?
Note you're using TARGET_PAGE_SIZE here - that's often smaller than the
host page size; that's probably a problem on non-x86, since you can't
free at that granularity.

>          } else if (!rs->ram_bulk_stage &&
> -                   !migration_in_postcopy() && migrate_use_xbzrle()) {
> +                   !migration_in_postcopy() && migrate_use_xbzrle() &&
> +                   !migrate_background_snapshot()) {
>              pages = save_xbzrle_page(rs, &p, current_addr, block,
>                                       offset, last_stage);
>              if (!last_stage) {
> @@ -1008,9 +1033,10 @@ static int ram_save_page(RAMState *rs, 
> PageSearchStatus *pss, bool last_stage)
>          ram_counters.transferred +=
>              save_page_header(rs, rs->f, block, offset | RAM_SAVE_FLAG_PAGE);
>          if (send_async) {
> -            qemu_put_buffer_async(rs->f, p, TARGET_PAGE_SIZE,
> -                                  migrate_release_ram() &
> -                                  migration_in_postcopy());
> +            bool may_free = migrate_background_snapshot() ||
> +                            (migrate_release_ram() &&
> +                             migration_in_postcopy());
> +            qemu_put_buffer_async(rs->f, p, TARGET_PAGE_SIZE, may_free);
>          } else {
>              qemu_put_buffer(rs->f, p, TARGET_PAGE_SIZE);
>          }
> @@ -1251,7 +1277,7 @@ static bool find_dirty_block(RAMState *rs, 
> PageSearchStatus *pss, bool *again)
>   * @rs: current RAM state
>   * @offset: used to return the offset within the RAMBlock
>   */
> -static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset)
> +static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset, void 
> **page_copy)
>  {
>      RAMBlock *block = NULL;
>  
> @@ -1261,10 +1287,14 @@ static RAMBlock *unqueue_page(RAMState *rs, 
> ram_addr_t *offset)
>                                  QSIMPLEQ_FIRST(&rs->src_page_requests);
>          block = entry->rb;
>          *offset = entry->offset;
> +        *page_copy = entry->page_copy;
>  
>          if (entry->len > TARGET_PAGE_SIZE) {
>              entry->len -= TARGET_PAGE_SIZE;
>              entry->offset += TARGET_PAGE_SIZE;
> +            if (entry->page_copy) {
> +                entry->page_copy += TARGET_PAGE_SIZE/sizeof(void*);

I don't think I understand why it's doing that.

> +            }
>          } else {
>              memory_region_unref(block->mr);
>              QSIMPLEQ_REMOVE_HEAD(&rs->src_page_requests, next_req);
> @@ -1291,9 +1321,10 @@ static bool get_queued_page(RAMState *rs, 
> PageSearchStatus *pss)
>      RAMBlock  *block;
>      ram_addr_t offset;
>      bool dirty;
> +    void *page_copy;
>  
>      do {
> -        block = unqueue_page(rs, &offset);
> +        block = unqueue_page(rs, &offset, &page_copy);
>          /*
>           * We're sending this page, and since it's postcopy nothing else
>           * will dirty it, and we must make sure it doesn't get sent again
> @@ -1331,6 +1362,7 @@ static bool get_queued_page(RAMState *rs, 
> PageSearchStatus *pss)
>           */
>          pss->block = block;
>          pss->page = offset >> TARGET_PAGE_BITS;
> +        pss->page_copy = page_copy;
>      }
>  
>      return !!block;
> @@ -1368,17 +1400,25 @@ static void migration_page_queue_free(RAMState *rs)
>   *
>   * @rbname: Name of the RAMBLock of the request. NULL means the
>   *          same that last one.
> + * @block: RAMBlock to use. block and rbname have mutualy exclusive
> + *         semantic with higher priority of the block.
>   * @start: starting address from the start of the RAMBlock
>   * @len: length (in bytes) to send
> + * @page_copy: the address the page should be written from
>   */
> -int ram_save_queue_pages(const char *rbname, ram_addr_t start, ram_addr_t 
> len)
> +int ram_save_queue_pages(RAMBlock *block, const char *rbname,
> +                         ram_addr_t start, ram_addr_t len, void* page_copy)

This is just used for postcopy at the moment - is it relevant to you?

>  {
>      RAMBlock *ramblock;
>      RAMState *rs = ram_state;
>  
>      ram_counters.postcopy_requests++;
> +
>      rcu_read_lock();
> -    if (!rbname) {
> +
> +    if (block) {
> +        ramblock = block;
> +    } else if (!rbname) {
>          /* Reuse last RAMBlock */
>          ramblock = rs->last_req_rb;
>  
> @@ -1413,6 +1453,7 @@ int ram_save_queue_pages(const char *rbname, ram_addr_t 
> start, ram_addr_t len)
>      new_entry->rb = ramblock;
>      new_entry->offset = start;
>      new_entry->len = len;
> +    new_entry->page_copy = page_copy;
>  
>      memory_region_ref(ramblock->mr);
>      qemu_mutex_lock(&rs->src_page_req_mutex);
> @@ -1450,7 +1491,8 @@ static int ram_save_target_page(RAMState *rs, 
> PageSearchStatus *pss,
>           * xbzrle can do better than compression.
>           */
>          if (migrate_use_compression() &&
> -            (rs->ram_bulk_stage || !migrate_use_xbzrle())) {
> +            (rs->ram_bulk_stage || !migrate_use_xbzrle()) &&
> +            !migrate_background_snapshot()) {
>              res = ram_save_compressed_page(rs, pss, last_stage);
>          } else {
>              res = ram_save_page(rs, pss, last_stage);
> @@ -1508,6 +1550,226 @@ static int ram_save_host_page(RAMState *rs, 
> PageSearchStatus *pss,
>      return pages;
>  }
>  
> +static bool ram_has_postcopy(void *opaque)
> +{
> +    return migrate_postcopy_ram();
> +}
> +
> +static int mem_protect(void *addr, uint64_t length, int prot)
> +{
> +    int ret = mprotect(addr, length, prot);
> +
> +    if (ret < 0) {
> +        error_report("%s: Can't change protection on ram block at %p (len: 
> %lu)",
> +                     __func__, addr, length);
> +    }
> +
> +    // 0 on success
> +    return ret;
> +}
> +
> +static int ram_set_ro(void* addr, uint64_t length)
> +{
> +    return mem_protect(addr, length, PROT_READ);
> +}
> +
> +static int ram_set_rw(void* addr, uint64_t length)
> +{
> +    return mem_protect(addr, length, PROT_READ | PROT_WRITE);
> +}

We need to keep these together so we know which bits to change for
userfault-wp

> +static RamBlockList ram_blocks;
> +
> +RamBlockList *ram_blocks_get(void)
> +{
> +    return &ram_blocks;
> +}
> +
> +void ram_blocks_fill(RamBlockList *blocks)
> +{
> +    RAMBlock *block = NULL;
> +
> +    qemu_mutex_lock_ramlist();
> +    QLIST_FOREACH(block, &ram_list.blocks, next) {

Look at how we use FOREACH_MIGRATABLE now

> +        memory_region_ref(block->mr);
> +        QLIST_INSERT_HEAD(blocks, block, bgs_next);
> +    }
> +    qemu_mutex_unlock_ramlist();
> +}
> +
> +void ram_blocks_clear(RamBlockList *blocks)
> +{
> +    RAMBlock *block = NULL;
> +
> +    QLIST_FOREACH(block, blocks, bgs_next) {
> +        QLIST_REMOVE(block, bgs_next);
> +        memory_region_unref(block->mr);
> +    }
> +}
> +
> +int ram_blocks_set_ro(RamBlockList *blocks)
> +{
> +    RAMBlock *block = NULL;
> +    int ret = 0;
> +
> +    QLIST_FOREACH(block, blocks, bgs_next) {
> +        ret = ram_set_ro(block->host, block->used_length);
> +        if (ret) {
> +            break;
> +        }
> +    }
> +
> +    return ret;
> +}
> +
> +int ram_blocks_set_rw(RamBlockList *blocks)
> +{
> +    RAMBlock *block = NULL;
> +    int ret = 0;
> +
> +    QLIST_FOREACH(block, blocks, bgs_next) {
> +        ret = ram_set_rw(block->host, block->used_length);
> +        if (ret) {
> +            break;
> +        }
> +    }
> +
> +    return ret;
> +}
> +
> +static void ram_page_buffer_decrease_used(void)
> +{
> +    qemu_event_reset(&ram_state->page_buffer.used_decreased);
> +    atomic_dec(&ram_state->page_buffer.used);
> +    qemu_event_set(&ram_state->page_buffer.used_decreased);
> +}
> +
> +static void ram_page_buffer_increase_used_wait(void)
> +{
> +    int ret, used, *used_ptr;
> +    RAMState *rs = ram_state;
> +    used_ptr = &rs->page_buffer.used;
> +    do {
> +        used = atomic_read(used_ptr);
> +        if (rs->page_buffer.capacity > used) {
> +            if ((ret = atomic_cmpxchg(used_ptr, used, used + 1)) == used) {
> +                return;
> +            } else {
> +                continue;
> +            }
> +        } else {
> +            qemu_event_wait(&rs->page_buffer.used_decreased);
> +        }
> +    } while(true);
> +}
> +
> +static void *ram_page_buffer_get(void)
> +{
> +    void *page;
> +    ram_page_buffer_increase_used_wait();
> +    page = mmap(0, TARGET_PAGE_SIZE, PROT_READ|PROT_WRITE,
> +                    MAP_PRIVATE|MAP_ANONYMOUS,
> +                    -1, 0);

Again TARGET_PAGE_SIZE is below host page size often.

> +   if (page == MAP_FAILED) {
> +       ram_page_buffer_decrease_used();
> +       page = NULL;
> +   }
> +   return page;
> +}
> +
> +static int ram_page_buffer_free(void *buffer)
> +{
> +    ram_page_buffer_decrease_used();
> +    return qemu_madvise(buffer, TARGET_PAGE_SIZE, MADV_DONTNEED);
> +}
> +
> +static int ram_try_copy_page(RAMBlock *block, unsigned long page_nr,
> +                             void** page_copy)
> +{
> +    void *host_page;

We could do with some more comments here;  is this called when you
notice a page is modified and need to start the copy?

> +    if (test_and_set_bit_atomic(page_nr, block->touched_map)) {

So you're marking it as written to, but it's already marked as
written to? (By another vCPU?)

> +        while (!test_bit_atomic(page_nr, block->copied_map)) {
> +            // the page is being copied -- wait for the end of the coping
> +            // and check once again
> +            qemu_event_reset(&ram_state->page_coping_done);
> +            qemu_event_wait(&ram_state->page_coping_done);
> +        }
> +        return 0;
> +    }
> +
> +    *page_copy = ram_page_buffer_get();
> +    if (!*page_copy) {
> +        return -1;
> +    }
> +
> +    host_page = block->host + (page_nr << TARGET_PAGE_BITS);
> +    memcpy(*page_copy, host_page, TARGET_PAGE_SIZE);
> +
> +    if (ram_set_rw(host_page, TARGET_PAGE_SIZE)) {
> +        ram_page_buffer_free(*page_copy);
> +        *page_copy = NULL;

Print some error messages - you've got quite a few places where you
fail with -1 but don't print anything to help know what happened.

> +        return -1;
> +    }
> +
> +    smp_mb();
> +    set_bit_atomic(page_nr, block->copied_map);
> +    qemu_event_set(&ram_state->page_coping_done);
> +
> +    return 1;
> +}
> +
> +static RAMBlock *find_ram_block(uint8_t *address, ram_addr_t *page_offset)
> +{
> +    RAMBlock *block = NULL;
> +
> +
> +    QLIST_FOREACH(block, ram_blocks_get(), bgs_next) {
> +        /* This case append when the block is not mapped. */
> +        if (block->host == NULL) {
> +            continue;
> +        }
> +
> +        if (address - block->host < block->max_length) {
> +            *page_offset = (address - block->host) & TARGET_PAGE_MASK;
> +            return block;
> +        }
> +    }
> +
> +    return NULL;
> +}

Isn't this the same as qemu_ram_block_from_host?

> +
> +// 0 - on success, 0 < - on error
> +int ram_process_page_fault(void *address)
> +{
> +    int ret;
> +    void *page_copy = NULL;
> +    unsigned long page_nr;
> +    ram_addr_t offset;
> +
> +    RAMBlock *block = find_ram_block(address, &offset);
> +
> +    if (!block) {
> +        return -1;
> +    }
> +
> +    page_nr = offset >> TARGET_PAGE_BITS;
> +
> +    ret = ram_try_copy_page(block, page_nr, &page_copy);
> +
> +    if (ret < 0) {
> +        return ret;
> +    } else if (ret > 0) {
> +        if (ram_save_queue_pages(block, NULL, offset,
> +                                 TARGET_PAGE_SIZE, page_copy)) {

Ah, so I guess you're using the queue for something other than postcopy
now - be careful, it's probably got other postcopy dependencies?

> +            ram_page_buffer_free(page_copy);
> +            return -1;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
>  /**
>   * ram_find_and_save_block: finds a dirty page and sends it to f
>   *
> @@ -1536,6 +1798,7 @@ static int ram_find_and_save_block(RAMState *rs, bool 
> last_stage)
>      pss.block = rs->last_seen_block;
>      pss.page = rs->last_page;
>      pss.complete_round = false;
> +    pss.page_copy = NULL;
>  
>      if (!pss.block) {
>          pss.block = QLIST_FIRST_RCU(&ram_list.blocks);
> @@ -1548,11 +1811,27 @@ static int ram_find_and_save_block(RAMState *rs, bool 
> last_stage)
>          if (!found) {
>              /* priority queue empty, so just search for something dirty */
>              found = find_dirty_block(rs, &pss, &again);
> +
> +            if (found && migrate_background_snapshot()) {
> +                // make a copy of the page and pass it to the page search 
> status
> +                int ret;
> +                ret = ram_try_copy_page(pss.block, pss.page, &pss.page_copy);
> +                if (ret == 0) {
> +                    found = false;
> +                    pages = 0;
> +                } else if(ret < 0) {
> +                    return ret;
> +                }
> +            }
>          }
>  
>          if (found) {
>              pages = ram_save_host_page(rs, &pss, last_stage);
>          }
> +
> +        if (pss.page_copy) {
> +            ram_page_buffer_decrease_used();
> +        }
>      } while (!pages && again);
>  
>      rs->last_seen_block = pss.block;
> @@ -1600,9 +1879,15 @@ static void xbzrle_load_cleanup(void)
>  
>  static void ram_state_cleanup(RAMState **rsp)
>  {
> +    if (migrate_background_snapshot()) {
> +        qemu_event_destroy(&(*rsp)->page_buffer.used_decreased);
> +        qemu_event_destroy(&(*rsp)->page_coping_done);
> +    }
> +
>      migration_page_queue_free(*rsp);
>      qemu_mutex_destroy(&(*rsp)->bitmap_mutex);
>      qemu_mutex_destroy(&(*rsp)->src_page_req_mutex);
> +
>      g_free(*rsp);
>      *rsp = NULL;
>  }
> @@ -1638,6 +1923,13 @@ static void ram_save_cleanup(void *opaque)
>          block->bmap = NULL;
>          g_free(block->unsentmap);
>          block->unsentmap = NULL;
> +
> +        if (migrate_background_snapshot()) {
> +            g_free(block->touched_map);
> +            block->touched_map = NULL;
> +            g_free(block->copied_map);
> +            block->copied_map = NULL;
> +        }
>      }
>  
>      xbzrle_cleanup();
> @@ -1652,6 +1944,9 @@ static void ram_state_reset(RAMState *rs)
>      rs->last_page = 0;
>      rs->last_version = ram_list.version;
>      rs->ram_bulk_stage = true;
> +
> +    rs->page_buffer.capacity = 1000; // in number of pages
> +    rs->page_buffer.used = 0;
>  }
>  
>  #define MAX_WAIT 50 /* ms, half buffered_file limit */
> @@ -2129,6 +2424,11 @@ static int ram_state_init(RAMState **rsp)
>       */
>      (*rsp)->migration_dirty_pages = ram_bytes_total() >> TARGET_PAGE_BITS;
>  
> +    if (migrate_background_snapshot()) {
> +        qemu_event_init(&ram_state->page_buffer.used_decreased, false);
> +        qemu_event_init(&ram_state->page_coping_done, false);
> +    }
> +
>      ram_state_reset(*rsp);
>  
>      return 0;
> @@ -2145,10 +2445,16 @@ static void ram_list_init_bitmaps(void)
>              pages = block->max_length >> TARGET_PAGE_BITS;
>              block->bmap = bitmap_new(pages);
>              bitmap_set(block->bmap, 0, pages);
> +
>              if (migrate_postcopy_ram()) {
>                  block->unsentmap = bitmap_new(pages);
>                  bitmap_set(block->unsentmap, 0, pages);
>              }
> +
> +            if (migrate_background_snapshot()) {
> +                block->touched_map = bitmap_new(pages);
> +                block->copied_map = bitmap_new(pages);
> +            }
>          }
>      }
>  }
> @@ -2974,11 +3280,6 @@ static int ram_load(QEMUFile *f, void *opaque, int 
> version_id)
>      return ret;
>  }
>  
> -static bool ram_has_postcopy(void *opaque)
> -{
> -    return migrate_postcopy_ram();
> -}
> -
>  static SaveVMHandlers savevm_ram_handlers = {
>      .save_setup = ram_save_setup,
>      .save_live_iterate = ram_save_iterate,
> diff --git a/migration/ram.h b/migration/ram.h
> index 64d81e9f1d..627c2efb51 100644
> --- a/migration/ram.h
> +++ b/migration/ram.h
> @@ -31,6 +31,7 @@
>  
>  #include "qemu-common.h"
>  #include "exec/cpu-common.h"
> +#include "exec/ramlist.h"
>  
>  extern MigrationStats ram_counters;
>  extern XBZRLECacheStats xbzrle_counters;
> @@ -45,7 +46,9 @@ int multifd_load_setup(void);
>  int multifd_load_cleanup(Error **errp);
>  
>  uint64_t ram_pagesize_summary(void);
> -int ram_save_queue_pages(const char *rbname, ram_addr_t start, ram_addr_t 
> len);
> +int ram_save_queue_pages(RAMBlock *block, const char *rbname,
> +                         ram_addr_t start, ram_addr_t len,
> +                         void* cached_page);
>  void acct_update_position(QEMUFile *f, size_t size, bool zero);
>  void ram_debug_dump_bitmap(unsigned long *todump, bool expected,
>                             unsigned long pages);
> @@ -61,5 +64,11 @@ void ram_handle_compressed(void *host, uint8_t ch, 
> uint64_t size);
>  int ramblock_recv_bitmap_test(RAMBlock *rb, void *host_addr);
>  void ramblock_recv_bitmap_set(RAMBlock *rb, void *host_addr);
>  void ramblock_recv_bitmap_set_range(RAMBlock *rb, void *host_addr, size_t 
> nr);
> +int ram_process_page_fault(void *address);
> +RamBlockList *ram_blocks_get(void);
> +void ram_blocks_fill(RamBlockList *blocks);
> +void ram_blocks_clear(RamBlockList *blocks);
> +int ram_blocks_set_ro(RamBlockList *blocks);
> +int ram_blocks_set_rw(RamBlockList *blocks);
>  
>  #endif
> -- 
> 2.17.0
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK