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, ben(a)skyportsystems.com wrote:
  From: Ben Warren <ben(a)skyportsystems.com>
 
 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 <ben(a)skyportsystems.com>
 Reviewed-by: Laszlo Ersek <lersek(a)redhat.com>
 ---
  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