Re: [SeaBIOS] [Qemu-devel] [RFC] Passing boot order from qemu to seabios

[Gleb Natapov <gleb@redhat.com>]

On Tue, Oct 12, 2010 at 10:35:51AM -0700, H. Peter Anvin wrote:
> On real hardware it is shared between BIOS and the OS, actually.
> 
Guest OS can write in qemu CMOS too. But what is it useful for? Most of
its content is not standard AFAIK.

> "Gleb Natapov" <gleb@redhat.com> wrote:
> 
> >On Tue, Oct 12, 2010 at 09:33:16AM -0700, H. Peter Anvin wrote:
> >> On 10/12/2010 01:01 AM, Gleb Natapov wrote:
> >> > On Mon, Oct 11, 2010 at 02:15:26PM -0700, H. Peter Anvin wrote:
> >> >>> I don't disagree.
> >> >>>
> >> >>> I think the best thing to do is to let SeaBIOS create a boot order table 
> >> >>> that contains descriptive information and then advertise that to QEMU.
> >> >>>
> >> >>> QEMU can then try to associate the list of bootable devices with it's 
> >> >>> own set of devices and select a preferred order that it can then give 
> >> >>> back to SeaBIOS.  SeaBIOS can then present that list to the user for 
> >> >>> additional refinement.
> >> >>
> >> >> Really, this kind of comes down to having a data structure that anything
> >> >> (Qemu, SeaBIOS and if needed the guest OS) can read and modify as needed.
> >> >>
> >> > But then QEMU and seabios will have to have shared storage they can
> >> > both write too. And this shared storage is part of VM now so you need
> >> > to carry it around when you move your VM elsewhere.
> >> >  
> >> 
> >> Yes, and it's part of real hardware, too.  It's usually called "the
> >> CMOS", short for CMOS RAM.
> >> 
> >On real hardware it is not shared between HW and bios. It is
> >written/read only by BIOS. In qemu it is not persistent and generated
> >for each qemu invocation. Previously it was used to pass config params
> >from qemu to a bios (and some legacy params are still passed that way),
> >but we moved to better interface for that (firmware config).
> >
> >--
> >			Gleb.
> 
> -- 
> Sent from my mobile phone.  Please pardon any lack of formatting.

--
			Gleb.