Re: [Qemu-devel] [PATCH 01/15] postcopy: Transmit and compare individual page sizes

[Juan Quintela]

"Dr. David Alan Gilbert (git)" <address@hidden> wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> When using postcopy with hugepages, we require the source
> and destination page sizes for any RAMBlock to match.
>
> Transmit them as part of the RAM information header and
> fail if there's a difference.
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  migration/ram.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index a1c8089..39998f5 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1970,6 +1970,9 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>          qemu_put_byte(f, strlen(block->idstr));
>          qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
>          qemu_put_be64(f, block->used_length);
> +        if (migrate_postcopy_ram() && block->page_size != 
> qemu_host_page_size) {
> +            qemu_put_be64(f, block->page_size);
> +        }

Hi

1- can different block have different page_size? 
2- can we remove the migrate_postocpy_ram() check and just send it for
   newer versions and not for older ones?

>      }
>  
>      rcu_read_unlock();
> @@ -2536,6 +2539,18 @@ static int ram_load(QEMUFile *f, void *opaque, int 
> version_id)
>                              error_report_err(local_err);
>                          }
>                      }
> +                    /* For postcopy we need to check hugepage sizes match */
> +                    if (migrate_postcopy_ram() &&
> +                        block->page_size != qemu_host_page_size) {
> +                        uint64_t remote_page_size = qemu_get_be64(f);
> +                        if (remote_page_size != block->page_size) {
> +                            error_report("Mismatched RAM page size %s "
> +                                         "(local) %" PRId64 "!= %" PRId64,
> +                                         id, block->page_size,
> +                                         remote_page_size);
> +                            ret = -EINVAL;
> +                        }
> +                    }
>                      ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG,
>                                            block->idstr);
>                  } else {