Re: [PATCH v7 4/6] libs/guest: move batch_pfns into a separate structure

[Frediano Ziglio <freddy77@xxxxxxxxx>]

On Thu, 9 Jul 2026 at 08:44, Frediano Ziglio <freddy77@xxxxxxxxx> wrote:
>
> From: Edwin Török <edwin.torok@xxxxxxxxxx>
>
> Prepare for following change.
>
> Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
> ---
> Changes since v6:
> - split from "libs/guest: allocate various migration arrays just once".
> ---
>  tools/libs/guest/xg_sr_common.h |  5 ++++-
>  tools/libs/guest/xg_sr_save.c   | 31 +++++++++++++++++--------------
>  2 files changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
> index f1573aefcb..7574c9f5b6 100644
> --- a/tools/libs/guest/xg_sr_common.h
> +++ b/tools/libs/guest/xg_sr_common.h
> @@ -239,11 +239,14 @@ struct xc_sr_context
>
>              struct precopy_stats stats;
>
> -            xen_pfn_t *batch_pfns;
>              unsigned int nr_batch_pfns;
>              unsigned long *deferred_pages;
>              unsigned long nr_deferred_pages;
>              xc_hypercall_buffer_t dirty_bitmap_hbuf;
> +            struct xc_sr_context_save_buffers
> +            {
> +                xen_pfn_t batch_pfns[MAX_BATCH_SIZE];
> +            } *buffers;
>          } save;
>
>          struct /* Restore data. */
> diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
> index 84fdbe4140..8956f4260d 100644
> --- a/tools/libs/guest/xg_sr_save.c
> +++ b/tools/libs/guest/xg_sr_save.c
> @@ -75,7 +75,7 @@ static int write_checkpoint_record(struct xc_sr_context 
> *ctx)
>
>  /*
>   * Writes a batch of memory as a PAGE_DATA record into the stream.  The batch
> - * is constructed in ctx->save.batch_pfns.
> + * is constructed in ctx->save.buffers->batch_pfns.
>   *
>   * This function:
>   * - gets the types for each pfn in the batch.
> @@ -95,6 +95,7 @@ static int write_batch(struct xc_sr_context *ctx)
>      void *page, *orig_page;
>      uint64_t *rec_pfns = NULL;
>      struct iovec *iov = NULL; int iovcnt = 0;
> +    xen_pfn_t *batch_pfns;

What about a direct

    xen_pfn_t *const batch_pfns = ctx->save.buffers->batch_pfns;

here ?

>      struct {
>          struct xc_sr_rhdr rec;
>          struct xc_sr_rec_page_data_header page_data;
> @@ -110,6 +111,10 @@ static int write_batch(struct xc_sr_context *ctx)
>      };
>
>      assert(nr_pfns != 0);
> +    assert(nr_pfns <= MAX_BATCH_SIZE);
> +    assert(ctx->save.buffers);
> +
> +    batch_pfns = ctx->save.buffers->batch_pfns;
>
>      /* Mfns of the batch pfns. */
>      mfns = malloc(nr_pfns * sizeof(*mfns));
> @@ -141,13 +146,12 @@ static int write_batch(struct xc_sr_context *ctx)

...

Frediano