On Wed, Nov 25, 2009 at 11:04:20PM +0100, Sebastian Herbszt wrote: >> Do different things during reset depending on CMOS values doesn't sound >> right to me. I don't know what is implemented right now. I thought that >> we reload BIOS on reset. > > Currently the BIOS seems to be only loaded once and not reloaded > during the life time of a VM. > I don't think there is a notion of BIOS reload on real hardware. CPU > access to it is either directed to the rom (power-up configuration, > all those fancy reset conditions) or to ram.
I see a "BIOS reload" as equivalent to directing access to rom. > How is shadowing currently implemented in qemu? Is the only BIOS > copy overwritten or is the rom copy separate from the ram copy? My understanding is that both the ram and rom are kept. (Though, on a "BIOS reload" I don't know if the ram is preserved.) To summarize the discussion so far, there seems to be a potential issue with reset: * If qemu doesn't reload the bios (a soft-reset) then there is a potential issue with the bios and option roms not running properly after a system reset invoked by Linux or other modern OSs. * If qemu does reload the bios (a hard-reset) then there is a good chance that old DOS programs will break when they invoke a reset in an attempt to switch from protected mode to real mode. Is that correct? -Kevin
