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SubjectRe: [RFC PATCH 1/1] PCI: skip release and reallocation of io port resources
On Tue, 06 Jul 2010 17:49:32 -0700
Yinghai Lu <yinghai@kernel.org> wrote:

> On 07/06/2010 04:58 PM, Linus Torvalds wrote:
> > On Tue, Jul 6, 2010 at 4:13 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> >>
> >> So you want to use pci=override_bios to reallocate all bios assigned resource include
> >> peer root buses resources and pci bridge resource and pci devices BAR?
> >
> > In a perfect world, we'd never need this at all, but sicne that's not
> > an option, the second-best alternative might be something like the
> > following:
> >
> > pci=override=off # default
> > pci=override=conflict # override only on conflicts
> > pci=override=<device> # clear BIOS allocations for <device> (and any
> > children, if it's a bus)
>
> current:
> if there is conflict, like pci bridge resources or pci devices resources is not in the scope of peer root bus resource range.
> or pci devices is not in pci bridge resources range.
> kernel would reject the resource and try to get new range in parent resource for the children.
>
> so current default is overriding the conflicts already.
>
> Maybe your conflicts have other meaning? like pci bridge resource size is not big enough?
>
> or we can have use
>
> pci=override=small_bridge
>
> or
>
> pci=override=bridges
>
> instead?

Changing the default (and fairly old) behavior at this point will
probably cause a lot of trouble; we have machines where reallocating
conflicting or apparently mis-programmed resources is needed.

But we can still add the pci=override= option. Your patch will need
some changes though; a user needing a specific bus/bridge reallocated
can just pass the bridge id. And rather than walking its way up,
freeing and trying to re-allocate, it could just free everything below
the given device and let the normal paths allocate it.

--
Jesse Barnes, Intel Open Source Technology Center


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