Re: [SeaBIOS] [RFC PATCH v2 4/4] pci: enable RedHat PCI bridges to reserve additional buses on PCI init

[Marcel Apfelbaum]

On 24/07/2017 17:39, Alexander Bezzubikov wrote:
> 2017-07-24 12:42 GMT+03:00 Gerd Hoffmann <[e-mail] 
> >:
> On Sun, 2017-07-23 at 22:44 +0300, Alexander Bezzubikov wrote:
> > By the way, any ideas on how to avoid 'bus overstealing' would 
> > be greatly appreciated.
> > Static BIOS variable isn't applicable since its value isn't saved
> > across reboots.
>
> I think the reservation hints should be a absolute number, not a
> increment.  i.e. if qemu suggests to reserve three extra bus numbers
> seabios should reserve three, no matter whenever there are zero, one,
> two or three child busses present.  And I guess seabios should
> interpret that as minimum, so in case it finds five child busses it
> will allocate five bus numbers of course ...
>
>
> Personally I have nothing against it. Marcel, Michael, what do you think?

Sounds good to me.
> Same with the other limit hints.  If the hint says to allocate 16M, and
> existing device bars sum up to 4M, allocate 16M (and therefore leave
> 12M address space for hotplug).  If the device bars sum up to 32M,
> allocate that.
>
> While being at it:  I have my doubts the capability struct layout
> (which mimics register layout) buys us that much, seabios wouldn't
> blindly copy over the values anyway.  Having regular u32 fields looks
> more useful to me.
>
>
> Again, if nobody has any objections, I can change it in v3.

I also had my reservations about prev layout, let's see
if it will look cleaner.

Thanks,
Marcel
> cheers,
>    Gerd