On Mon, Oct 12, 2009 at 08:44:56AM -0500, Anthony Liguori wrote: > Gleb Natapov wrote >>> BTW, I don't think it's write-protected and it probably should be? >>> >>> >> AFAIR it is not writable on plain qemu. >> > > KVM wants it to be writable for the TPR optimization. Historically, it > was read-only in QEMU but it changed to read-write in order to fake > coreboot into thinking that the bios implemented PMM which it doesn't. During init, SeaBIOS will enable writes to all memory between 0xc0000-0x100000 - shadowing the ram as needed. Just prior to starting the boot phase, SeaBIOS will make the bios f-segment and all option roms read only. (Note, this differs from bochs-bios which doesn't make optionroms writable - seabios makes them writable because some optionroms need it.) As an aside, it would be nice if qemu would just start off with this memory as read/writable, as the shadoing process is ugly, it's qemu specific, and it always ends up as read/writable anyway. I'm not sure where coreboot or PMM comes into this. SeaBIOS does implement the Post Memory Manager calls. -Kevin -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
