Re: [Qemu-devel] [PATCH v2 4/5] migration: Convert ram to use new load_setup()/load_cleanup()

[Dr. David Alan Gilbert]

* Juan Quintela (address@hidden) wrote:
> Once there, I rename ram_migration_cleanup() to ram_save_cleanup().
> Notice that this is the first pass, and I only passed XBZRLE to the
> new scheme.  Moved decoded_buf to inside XBZRLE struct.
> As a bonus, I don't have to export xbzrle functions from ram.c.
> 
> Signed-off-by: Juan Quintela <address@hidden>
> ---
>  migration/migration.c |  3 ---
>  migration/ram.c       | 52 
> +++++++++++++++++++++++++++++++++++----------------
>  migration/ram.h       |  1 -
>  3 files changed, 36 insertions(+), 20 deletions(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 0799424..98f2ee1 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -350,9 +350,6 @@ static void process_incoming_migration_co(void *opaque)
>          migrate_decompress_threads_join();
>          exit(EXIT_FAILURE);
>      }
> -
> -    free_xbzrle_decoded_buf();
> -
>      mis->bh = qemu_bh_new(process_incoming_migration_bh, mis);
>      qemu_bh_schedule(mis->bh);
>  }
> diff --git a/migration/ram.c b/migration/ram.c
> index be78e42..7040809 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -85,11 +85,10 @@ static struct {
>      QemuMutex lock;
>      /* it will store a page full of zeros */
>      uint8_t *zero_target_page;
> +    /* buffer used for XBZRLE decoding */
> +    uint8_t *decoded_buf;
>  } XBZRLE;
>  
> -/* buffer used for XBZRLE decoding */
> -static uint8_t *xbzrle_decoded_buf;
> -
>  static void XBZRLE_cache_lock(void)
>  {
>      if (migrate_use_xbzrle())
> @@ -1350,13 +1349,18 @@ uint64_t ram_bytes_total(void)
>      return total;
>  }
>  
> -void free_xbzrle_decoded_buf(void)
> +static void xbzrle_load_setup(void)
>  {
> -    g_free(xbzrle_decoded_buf);
> -    xbzrle_decoded_buf = NULL;
> +    XBZRLE.decoded_buf = g_malloc(TARGET_PAGE_SIZE);
>  }
>  
> -static void ram_migration_cleanup(void *opaque)
> +static void xbzrle_load_cleanup(void)
> +{
> +    g_free(XBZRLE.decoded_buf);
> +    XBZRLE.decoded_buf = NULL;
> +}
> +
> +static void ram_save_cleanup(void *opaque)
>  {
>      RAMState **rsp = opaque;
>      RAMBlock *block;
> @@ -2076,12 +2080,6 @@ static int load_xbzrle(QEMUFile *f, ram_addr_t addr, 
> void *host)
>  {
>      unsigned int xh_len;
>      int xh_flags;
> -    uint8_t *loaded_data;
> -
> -    if (!xbzrle_decoded_buf) {
> -        xbzrle_decoded_buf = g_malloc(TARGET_PAGE_SIZE);
> -    }
> -    loaded_data = xbzrle_decoded_buf;
>  
>      /* extract RLE header */
>      xh_flags = qemu_get_byte(f);
> @@ -2097,10 +2095,10 @@ static int load_xbzrle(QEMUFile *f, ram_addr_t addr, 
> void *host)
>          return -1;
>      }
>      /* load data and decode */
> -    qemu_get_buffer_in_place(f, &loaded_data, xh_len);
> +    qemu_get_buffer_in_place(f, &XBZRLE.decoded_buf, xh_len);

No !  Note the & - loaded_data can get changed at that point to
point to an internal buffer rather than using that temporary.

So you still need the loaded_data and use that in the rest of
this function.

Dave

>      /* decode RLE */
> -    if (xbzrle_decode_buffer(loaded_data, xh_len, host,
> +    if (xbzrle_decode_buffer(XBZRLE.decoded_buf, xh_len, host,
>                               TARGET_PAGE_SIZE) == -1) {
>          error_report("Failed to load XBZRLE page - decode error!");
>          return -1;
> @@ -2304,6 +2302,26 @@ static void 
> decompress_data_with_multi_threads(QEMUFile *f,
>  }
>  
>  /**
> + * ram_load_setup: Setup RAM for migration incoming side
> + *
> + * Returns zero to indicate success and negative for error
> + *
> + * @f: QEMUFile where to receive the data
> + * @opaque: RAMState pointer
> + */
> +static int ram_load_setup(QEMUFile *f, void *opaque)
> +{
> +    xbzrle_load_setup();
> +    return 0;
> +}
> +
> +static int ram_load_cleanup(void *opaque)
> +{
> +    xbzrle_load_cleanup();
> +    return 0;
> +}
> +
> +/**
>   * ram_postcopy_incoming_init: allocate postcopy data structures
>   *
>   * Returns 0 for success and negative if there was one error
> @@ -2611,7 +2629,9 @@ static SaveVMHandlers savevm_ram_handlers = {
>      .save_live_complete_precopy = ram_save_complete,
>      .save_live_pending = ram_save_pending,
>      .load_state = ram_load,
> -    .save_cleanup = ram_migration_cleanup,
> +    .save_cleanup = ram_save_cleanup,
> +    .load_setup = ram_load_setup,
> +    .load_cleanup = ram_load_cleanup,
>  };
>  
>  void ram_mig_init(void)
> diff --git a/migration/ram.h b/migration/ram.h
> index 6272eb0..a8b79a4 100644
> --- a/migration/ram.h
> +++ b/migration/ram.h
> @@ -47,7 +47,6 @@ void migrate_decompress_threads_join(void);
>  uint64_t ram_pagesize_summary(void);
>  int ram_save_queue_pages(const char *rbname, ram_addr_t start, ram_addr_t 
> len);
>  void acct_update_position(QEMUFile *f, size_t size, bool zero);
> -void free_xbzrle_decoded_buf(void);
>  void ram_debug_dump_bitmap(unsigned long *todump, bool expected,
>                             unsigned long pages);
>  void ram_postcopy_migrated_memory_release(MigrationState *ms);
> -- 
> 2.9.4
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK