linux-kernel - Re: SNB PCI root information

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Message-ID: <CAErSpo4x8+M6hGAqJR2rjGEGk2AnnZfJkmaJrJedzhnKiRf2qw@mail.gmail.com>
Date:	Wed, 20 Jun 2012 11:17:52 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ulrich Drepper <drepper@...il.com>, jbarnes@...tuousgeek.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	lenb@...nel.org, x86@...nel.org, linux-pci@...r.kernel.org
Subject: Re: SNB PCI root information

On Tue, Jun 19, 2012 at 12:20 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> On Tue, Jun 19, 2012 at 5:36 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>>
>> I'm not opposed to something like this, if people think it's useful.
>>
>> This patch sets the node quite early, before we even look at the _PXM
>> information in pci_acpi_scan_root().  That means if the BIOS does
>> supply a _PXM method and the user gives this argument, the
>> user-supplied info is silently overwritten.  To me it would make more
>> sense to handle an option like this *after* we look for _PXM info.
>> That way it could be used to compensate for both missing and incorrect
>> _PXM info.
>
> yes, we can only let user input and hostbridge touch that array.
>
> but i'd like to only handle missing _PXM case.
>
> If the BIOS provide wrong _PXM, that BIOS really should be fixed at first.

I don't understand this.  Is there an *advantage* to silently throwing
away the information the user specified on the command line?  If the
user goes to the trouble of discovering and using a command line
argument, I think that user-supplied information should override
anything the kernel can figure out on its own.  Ulrich, do you have an
opinion either way?
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