[Qemu-devel] Re: [PATCH] floppy: save and restore DIR register

[Jason Wang]

Paolo Bonzini writes:
 > On 03/25/2011 07:27 AM, Jason Wang wrote:
 > > We need to keep DIR register unchanged across migration, but currently it
 > > depends on the media_changed flags from block layer and we do not 
 > > save/restore
 > > it which could let the guest driver think the floppy have changed after
 > > migration. To fix this, a new filed media_changed in FDrive strcutre was
 > > introduced in order to save and restore the it from block layer through
 > > pre_save/post_load callbacks.
 > 
 > I guess you can avoid saving if the media changed flag is zero, too 
 > (which should be the common case after the guest has booted, right?).
 > 
 > Paolo
 > 

Yes, zero is the common case, but the bdrv_open() called by listening qemu in
dest mode would always set the media_changed to one, so we must save and restore
it during migration.