linux-kernel - Re: [PATCH 16/16 v6] PCI: document the new PCI boot parameters

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Date:	Sun, 9 Nov 2008 15:34:33 +0100
From:	Alexander Graf <agraf@...e.de>
To:	Pavel Machek <pavel@...e.cz>
Cc:	Greg KH <greg@...ah.com>, "Zhao, Yu" <yu.zhao@...el.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"achiang@...com" <achiang@...com>,
	"grundler@...isc-linux.org" <grundler@...isc-linux.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"matthew@....cx" <matthew@....cx>,
	"randy.dunlap@...cle.com" <randy.dunlap@...cle.com>,
	"rdreier@...co.com" <rdreier@...co.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 16/16 v6] PCI: document the new PCI boot parameters

>>>>> If we do resource rebalance after system is up, do you think  
>>>>> there is any
>>>>> side effect or impact to other subsystem other than PCI (e.g.  
>>>>> MTRR)?
>>>> I don't think so.
>>>>> I haven't had much thinking on the dynamical resource rebalance.  
>>>>> If you
>>>>> have any idea about this, can you please suggest?
>>>> Yeah, it's going to be hard :)
>>>> We've thought about this in the past, and even Microsoft said it  
>>>> was
>>>> going to happen for Vista, but they realized in the end, like we  
>>>> did a
>>>> few years previously, that it would require full support of all PCI
>>>> drivers as well (if you rebalance stuff that is already bound to a
>>>> driver.)  So they dropped it.
>>>> When would you want to do this kind of rebalancing?  Before any PCI
>>>> driver is bound to any devices?  Or afterwards?
>>>
>>> I guess if we want the rebalance dynamic, then we should have it  
>>> full --
>>> the rebalance would be functional even after the driver is loaded.
>>>
>>> But in most cases, there will be problem when we unload driver  
>>> from a hard
>>> disk controller, etc. We can mount root on a ramdisk and do the  
>>> rebalance
>>> there, but it's complicated for a real user.
>>>
>>> So looks like doing rebalancing before any driver is bound to any  
>>> device is
>>> also a nice idea, if user can get a shell to do rebalance before  
>>> built-in
>>> PCI driver grabs device.
>>
>> That's not going to work, it needs to happen before any PCI device is
>> bound, which is before init runs.
>
> We could run shell from early initrd... And PCI is not required for
> initrd, right?

You can't be sure of that - compile your ATA driver =y and you'll  
definitely end up using PCI.

Alex
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