* Ashijeet Acharya (ashijeetacha...@gmail.com) wrote:
> Migration of a "none" machine with no RAM crashes abruptly as
> bitmap_new() fails and thus aborts. Instead place zero RAM checks at
> appropriate places to skip migration of RAM in this case and complete
> migration successfully for devices only.
>
> Signed-off-by: Ashijeet Acharya <ashijeetacha...@gmail.com>
Yes it seems to work, but there is a small bug,
if we look at:
static void ram_migration_cleanup(void *opaque)
{
/* caller have hold iothread lock or is in a bh, so there is
* no writing race against this migration_bitmap
*/
struct BitmapRcu *bitmap = migration_bitmap_rcu;
atomic_rcu_set(&migration_bitmap_rcu, NULL);
if (bitmap) {
memory_global_dirty_log_stop();
call_rcu(bitmap, migration_bitmap_free, rcu);
}
we see it doesn't cause memory_global_dirty_log_stop
if migration_bitmap_rcu is NULL; so we end up
still calling dirty_log_start in ram_save_init but
never call stop.
I suggest you change it to:
migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
if (ram_bytes_total()) {
ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
migration_bitmap_rcu->bmap = bitmap_new(ram_bitmap_pages);
bitmap_set(migration_bitmap_rcu->bmap, 0, ram_bitmap_pages);
The cleanup routine still causes the dirty_log_stop() then.
Dave
> ---
> Changes in v2:
> - try to migrate successfully by skipping RAM (Paolo, Greg)
> - drop the idea of erroring out and failing nicely
> migration/ram.c | 22 +++++++++++++++-------
> 1 file changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index ef8fadf..2f19566 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1325,6 +1325,11 @@ static int ram_find_and_save_block(QEMUFile *f, bool
> last_stage,
> ram_addr_t dirty_ram_abs; /* Address of the start of the dirty page in
> ram_addr_t space */
>
> + /* No dirty page as there is zero RAM */
> + if (!ram_bytes_total()) {
> + return pages;
> + }
> +
> pss.block = last_seen_block;
> pss.offset = last_offset;
> pss.complete_round = false;
> @@ -1912,14 +1917,17 @@ static int ram_save_init_globals(void)
> bytes_transferred = 0;
> reset_ram_globals();
>
> - ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> - migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
> - migration_bitmap_rcu->bmap = bitmap_new(ram_bitmap_pages);
> - bitmap_set(migration_bitmap_rcu->bmap, 0, ram_bitmap_pages);
> + /* Skip setting bitmap if there is no RAM */
> + if (ram_bytes_total()) {
> + ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> + migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
> + migration_bitmap_rcu->bmap = bitmap_new(ram_bitmap_pages);
> + bitmap_set(migration_bitmap_rcu->bmap, 0, ram_bitmap_pages);
>
> - if (migrate_postcopy_ram()) {
> - migration_bitmap_rcu->unsentmap = bitmap_new(ram_bitmap_pages);
> - bitmap_set(migration_bitmap_rcu->unsentmap, 0, ram_bitmap_pages);
> + if (migrate_postcopy_ram()) {
> + migration_bitmap_rcu->unsentmap = bitmap_new(ram_bitmap_pages);
> + bitmap_set(migration_bitmap_rcu->unsentmap, 0, ram_bitmap_pages);
> + }
> }
>
> /*
> --
> 2.6.2
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
