Re: [PATCH v3 08/13] migration/ram: Simplify host page handling in ram_load_postcopy()

[Dr. David Alan Gilbert]

* David Hildenbrand (address@hidden) wrote:
> Add two new helper functions. This will in come handy once we want to
> handle ram block resizes while postcopy is active.
> 
> Cc: "Dr. David Alan Gilbert" <address@hidden>
> Cc: Juan Quintela <address@hidden>
> Cc: Peter Xu <address@hidden>
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>  migration/ram.c | 54 ++++++++++++++++++++++++++++---------------------
>  1 file changed, 31 insertions(+), 23 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index d5a4d69e1c..f815f4e532 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2734,6 +2734,20 @@ static inline void 
> *host_from_ram_block_offset(RAMBlock *block,
>      return block->host + offset;
>  }
>  
> +static void *host_page_from_ram_block_offset(RAMBlock *block,
> +                                             ram_addr_t offset)
> +{
> +    /* Note: Explicitly no check against offset_in_ramblock(). */
> +    return (void *)QEMU_ALIGN_DOWN((uintptr_t)block->host + offset,
> +                                   block->page_size);
> +}
> +
> +static ram_addr_t host_page_offset_from_ram_block_offset(RAMBlock *block,
> +                                                         ram_addr_t offset)
> +{
> +    return ((uintptr_t)block->host + offset) & (block->page_size - 1);
> +}
> +
>  static inline void *colo_cache_from_block_offset(RAMBlock *block,
>                                                   ram_addr_t offset)
>  {
> @@ -3111,13 +3125,12 @@ static int ram_load_postcopy(QEMUFile *f)
>      MigrationIncomingState *mis = migration_incoming_get_current();
>      /* Temporary page that is later 'placed' */
>      void *postcopy_host_page = mis->postcopy_tmp_page;
> -    void *this_host = NULL;
> +    void *host_page = NULL;
>      bool all_zero = false;
>      int target_pages = 0;
>  
>      while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
>          ram_addr_t addr;
> -        void *host = NULL;
>          void *page_buffer = NULL;
>          void *place_source = NULL;
>          RAMBlock *block = NULL;
> @@ -3143,9 +3156,12 @@ static int ram_load_postcopy(QEMUFile *f)
>          if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE |
>                       RAM_SAVE_FLAG_COMPRESS_PAGE)) {
>              block = ram_block_from_stream(f, flags);
> +            if (!block) {
> +                ret = -EINVAL;

Could we have an error_report there, at the moment it would trigger
the one below.

Other than that,


Reviewed-by: Dr. David Alan Gilbert <address@hidden>


> +                break;
> +            }
>  
> -            host = host_from_ram_block_offset(block, addr);
> -            if (!host) {
> +            if (!offset_in_ramblock(block, addr)) {
>                  error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
>                  ret = -EINVAL;
>                  break;
> @@ -3163,21 +3179,18 @@ static int ram_load_postcopy(QEMUFile *f)
>               * of a host page in one chunk.
>               */
>              page_buffer = postcopy_host_page +
> -                          ((uintptr_t)host & (block->page_size - 1));
> +                          host_page_offset_from_ram_block_offset(block, 
> addr);
>              /* If all TP are zero then we can optimise the place */
>              if (target_pages == 1) {
>                  all_zero = true;
> -                this_host = (void *)QEMU_ALIGN_DOWN((uintptr_t)host,
> -                                                    block->page_size);
> -            } else {
> +                host_page = host_page_from_ram_block_offset(block, addr);
> +            } else if (host_page != host_page_from_ram_block_offset(block,
> +                                                                    addr)) {
>                  /* not the 1st TP within the HP */
> -                if (QEMU_ALIGN_DOWN((uintptr_t)host, block->page_size) !=
> -                    (uintptr_t)this_host) {
> -                    error_report("Non-same host page %p/%p",
> -                                  host, this_host);
> -                    ret = -EINVAL;
> -                    break;
> -                }
> +                error_report("Non-same host page %p/%p", host_page,
> +                             host_page_from_ram_block_offset(block, addr));
> +                ret = -EINVAL;
> +                break;
>              }
>  
>              /*
> @@ -3257,16 +3270,11 @@ static int ram_load_postcopy(QEMUFile *f)
>          }
>  
>          if (!ret && place_needed) {
> -            /* This gets called at the last target page in the host page */
> -            void *place_dest = (void *)QEMU_ALIGN_DOWN((uintptr_t)host,
> -                                                       block->page_size);
> -
>              if (all_zero) {
> -                ret = postcopy_place_page_zero(mis, place_dest,
> -                                               block);
> +                ret = postcopy_place_page_zero(mis, host_page, block);
>              } else {
> -                ret = postcopy_place_page(mis, place_dest,
> -                                          place_source, block);
> +                ret = postcopy_place_page(mis, host_page, place_source,
> +                                          block);
>              }
>          }
>      }
> -- 
> 2.24.1
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK