Re: [SeaBIOS] [PATCH v7 5/5] QEMU fw_cfg: Write fw_cfg back on S3 resume

[Kevin O'Connor]

On Mon, Feb 20, 2017 at 07:56:19PM -0800, [e-mail] wrote:
> From: Ben Warren <[e-mail]>
>
> Any pointers to BIOS-allocated memory that were written back to QEMU
> fw_cfg files are replayed when resuming from S3 sleep.
>
> Signed-off-by: Ben Warren <[e-mail]>
> Reviewed-by: Laszlo Ersek <[e-mail]>
> ---
>  src/fw/romfile_loader.c | 33 +++++++++++++++++++++++++++++++++
>  src/fw/romfile_loader.h |  2 ++
>  src/resume.c            |  4 ++++
>  3 files changed, 39 insertions(+)
>
> diff --git a/src/fw/romfile_loader.c b/src/fw/romfile_loader.c
> index 30e7b58..14bc908 100644
> --- a/src/fw/romfile_loader.c
> +++ b/src/fw/romfile_loader.c
> @@ -4,6 +4,7 @@
>  #include "string.h" // strcmp
>  #include "romfile.h" // struct romfile_s
>  #include "malloc.h" // Zone*, _malloc
> +#include "list.h" // struct hlist_node
>  #include "output.h" // warn_*
>  #include "paravirt.h" // qemu_cfg_write_file
>
> @@ -16,6 +17,16 @@ struct romfile_loader_files {
>      struct romfile_loader_file files[];
>  };
>
> +// Data structures for storing "write pointer" entries for possible replay
> +struct romfile_wr_pointer_entry {
> +    u64 pointer;
> +    u32 offset;
> +    u16 key;
> +    u8 ptr_size;
> +    struct hlist_node node;
> +};
> +static struct hlist_head romfile_pointer_list;
> +
>  static struct romfile_loader_file *
>  romfile_loader_find(const char *name,
>                      struct romfile_loader_files *files)
> @@ -29,6 +40,19 @@ romfile_loader_find(const char *name,
>      return NULL;
>  }
>
> +// Replay "write pointer" entries back to QEMU
> +void romfile_fw_cfg_resume(void)
> +{
> +    if (!CONFIG_QEMU)
> +        return;
> +
> +    struct romfile_wr_pointer_entry *entry;
> +    hlist_for_each_entry(entry, &romfile_pointer_list, node) {
> +        qemu_cfg_write_file_simple(&entry->pointer, entry->key,
> +                                   entry->offset, entry->ptr_size);
> +    }
> +}
> +
>  static void romfile_loader_allocate(struct romfile_loader_entry_s *entry,
>                                      struct romfile_loader_files *files)
>  {
> @@ -163,6 +187,15 @@ static void romfile_loader_write_pointer(struct romfile_loader_entry_s *entry,
>                              entry->wr_pointer.size) != entry->wr_pointer.size) {
>          goto err;
>      }
> +
> +    /* Store the info so it can replayed later if necessary */
> +    struct romfile_wr_pointer_entry *store = malloc_high(sizeof(*store));
> +    store->pointer = pointer;

I missed this in my earlier review - it's necessary to always check
the return of malloc() in seabios.  (Writing to NULL changes memory at
address 0 which is shared with the 16bit interrupt table.)  I fixed it
upon commit.

-Kevin