[SeaBIOS] [PATCH v3 4/6] pci: init boot devices only on address space shortage

[Gleb Natapov]

On Wed, Jul 06, 2011 at 10:57:41AM +0200, Gerd Hoffmann wrote:
> On 07/05/11 18:23, Michael S. Tsirkin wrote:
> >On Tue, Jul 05, 2011 at 05:27:03PM +0200, Gerd Hoffmann wrote:
> >>Try to handle address space shortage by skipping any device
> >>which isn't essential for boot.
> >>
> >>Signed-off-by: Gerd Hoffmann<kraxel at redhat.com>
> >
> >At least in a virt setup, it's much easier to debug
> >things if boot just fails. Partial boot could be an option I guess.
> 
> Yea, I think that is pretty much the fundamental question.  Does it
> make sense to try boot up even if we can't fit some devices into the
> pci memory hole.
> 
> At least linux guests will try to map devices below the pci memory
> hole in case seabios didn't assign an address.  Of course this works
> only if the guest hasn't too much memory so there is some free space
> between end of ram and the start of the pci memory hole.
> 
> >We usually have a list of bootable devices we got from qemu -
> >want to use that?
> 
> Why?  seabios knows itself which devices it can use to boot.  Also
> the list from qemu is incomplete, the boot menu can have more
> entries than what we get passed in from qemu as boot order list.
> 
Correct. Boot order contains only devices with assigned priorities. It
still makes sense to try to configure them first since if user assigned
boot priority he expects to boot from one of them. I wouldn't complicate
the patch to much for that pathological case though.

--
			Gleb.