On 01/17/17 15:41, Michael S. Tsirkin wrote: > On Tue, Jan 17, 2017 at 02:00:58PM +0100, Igor Mammedov wrote: >> Question is how you'd get address of it and I think that's where >> writable fwcfg files come in play. >> I'd prefer fwcfg_loader in firmware to write it back after buffer >> allocation is done as it's already has utilities for fw_cfg, >> but that probably would mean extending loader protocol to support >> new writeback command. > > Right. It's quite easy to do as at least seabios was written to > ignore commands it does not recognize. So with old bios you > just don't get a write. Not sure about UEFI, worth checking.
Same; OVMF skips (and logs) unknown commands. > >> PS, address one would get from guest should be migrated as well > > IIRC writeable fw cfg blobs are migrated automatically. > When added with rom_add_blob() or derivative functions / function-like macros, they are. Thanks Laszlo
