Re: [PATCH 3/6] migration/postcopy: count target page number to decide the place_needed

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Wei Yang (richardw.yang@linux.intel.com) wrote:
> In postcopy, it requires to place whole host page instead of target
> page.
> 
> Currently, it relies on the page offset to decide whether this is the
> last target page. We also can count the target page number during the
> iteration. When the number of target page equals
> (host page size / target page size), this means it is the last target
> page in the host page.
> 
> This is a preparation for non-ordered target page transmission.
> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/ram.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index f59e3fe197..5c05376d8d 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -4017,6 +4017,7 @@ static int ram_load_postcopy(QEMUFile *f)
>      void *postcopy_host_page = mis->postcopy_tmp_page;
>      void *last_host = NULL;
>      bool all_zero = false;
> +    int target_pages = 0;
>  
>      while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
>          ram_addr_t addr;
> @@ -4051,6 +4052,7 @@ static int ram_load_postcopy(QEMUFile *f)
>                  ret = -EINVAL;
>                  break;
>              }
> +            target_pages++;
>              matches_target_page_size = block->page_size == TARGET_PAGE_SIZE;
>              /*
>               * Postcopy requires that we place whole host pages atomically;
> @@ -4082,8 +4084,10 @@ static int ram_load_postcopy(QEMUFile *f)
>               * If it's the last part of a host page then we place the host
>               * page
>               */
> -            place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) &
> -                                     (block->page_size - 1)) == 0;
> +            if (target_pages == (block->page_size / TARGET_PAGE_SIZE)) {
> +                place_needed = true;
> +                target_pages = 0;
> +            }
>              place_source = postcopy_host_page;
>          }
>          last_host = host;
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK