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

[Marcel Apfelbaum <marcel@redhat.com>]

On 24/07/2017 17:39, Alexander Bezzubikov wrote:
> 2017-07-24 12:42 GMT+03:00 Gerd Hoffmann <kraxel@redhat.com 
> <mailto:kraxel@redhat.com>>:
> 
>     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
> 
> 
> 
> 
> -- 
> Alexander Bezzubikov