Re: [PATCH] PCI: conditional resource-reallocation through kernel parameter pci=realloc

From: Ram Pai <linuxram@us.ibm.com>
To: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>,
	torvalds@linux-foundation.org, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org, yinghai@kernel.org
Subject: Re: [PATCH] PCI: conditional resource-reallocation through kernel parameter pci=realloc
Date: Thu, 30 Jun 2011 11:38:16 -0700	[thread overview]
Message-ID: <20110630183816.GA20268@ram-laptop> (raw)
In-Reply-To: <4E0CAE86.6020901@hartkopp.net>

On Thu, Jun 30, 2011 at 07:12:38PM +0200, Oliver Hartkopp wrote:
> On 30.06.2011 19:07, Jesse Barnes wrote:
> > On Thu, 30 Jun 2011 19:04:55 +0200
> > Oliver Hartkopp <socketcan@hartkopp.net> wrote:
> > 
> >> On 30.06.2011 10:09, Ram Pai wrote:
> >>> Multiple attempts to dynamically reallocate pci resources have unfortunately
> >>> lead to regressions. Though we continue to fix the regressions and fine tune the
> >>> dynamic-reallocation behavior, we have not reached a acceptable state yet.
> >>>
> >>> This patch provides a interim solution. It disables dynamic-reallocation; by
> >>> default, with the ability to enable it through pci=realloc kernel command line
> >>> parameter.
> >>
> >> What is the advantage of creating an 'interim' kernel parameter instead of
> >> reverting the problematic commit and queue up a proper solution for 3.1 ?
> >>
> >> A kernel parameter needs to be observed, documented and set appropriately.
> >>
> >> I would prefer to have an automatic solution - if not in 3.0 then in 3.1 ...
> > 
> > Yeah, we all want an automatic solution, but we still haven't been able
> > to achieve one.  My hope is that a parameter will let us keep the code
> > upstream for Ram and others to keep fixing, then we can move to using
> > it by default in some future release.  Keeping the code upstream but
> > behind a param should make development easier; at least that's the goal.
> 
> What's wrong with the "[PATCH 0/4 v2] PCI: fix cardbus and sriov regressions"?
> To me it looked good - or don't you trust that fix right now?

I trust the fix :).

Linus's concern was the wrong alignment, which I have fixed, but yet to resend
the patchset. Will do today.

However Linus's other concern was "too late for 3.0.0, for such a large patch".

There is the other concern about "should cardbus resources be treated nice-to-have?"

Also we dont know yet, what other platforms we have broken in some unique way.

RP