>>> On 19.05.11 at 07:33, Daniel Castro <[email protected]> wrote: > In order to give PV Drivers to SeaBIOS we will need to solve a few > problems, one is the following: > Does a booting kernel informs the BIOS that it will leave real mode > and not use it again? When the booting kernel uses CPU real mode for > the last time, how can we (Xen or SeaBIOS) know that real mode will no > longer be used, and hence BIOS calls will not be issued? > We want upon last real mode usage to leave all Xen PV information in a > clean state, this means, closing the channel and ring between the > newly created domain and the host system.
How can you be certain an OS won't switch back to real mode even after an extended period of up-time? Or that such switching back would affect you (could be calling e.g. the video or PCI BIOS functions only). There is INT15 AX=EC00 with BX specifying the target operating mode, but that's apparently being called only before entering long mode (i.e. wouldn't cover 32-bit OSes). And it would neither be a guarantee that the OS might not later return to real mode. Jan _______________________________________________ SeaBIOS mailing list [email protected] http://www.seabios.org/mailman/listinfo/seabios
