linux-kernel - Re: [PATCH v2 2/5] x86/PCI: Support additional MMIO range capabilities

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Date:	Wed, 30 Apr 2014 02:50:21 -0500
From:	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:	Robert Richter <rric@...nel.org>,
	Myron Stowe <myron.stowe@...il.com>
CC:	Borislav Petkov <bp@...en8.de>, Borislav Petkov <bp@...e.de>,
	"Andreas Herrmann" <herrmann.der.user@...glemail.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Myron Stowe <myron.stowe@...hat.com>,
	"Aravind Gopalakrishnan" <aravind.gopalakrishnan@....com>,
	linux-pci <linux-pci@...r.kernel.org>, <kim.naru@....com>,
	Daniel J Blueman <daniel@...ascale.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86 <x86@...nel.org>,
	Steffen Persvold <sp@...ascale.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Jan Beulich" <JBeulich@...e.com>, Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH v2 2/5] x86/PCI: Support additional MMIO range capabilities



On 04/30/2014 02:00 AM, Robert Richter wrote:
> On 29.04.14 15:40:28, Myron Stowe wrote:
>> On Tue, Apr 29, 2014 at 1:14 PM, Borislav Petkov <bp@...en8.de> wrote:
>>> So sounds to me like we want to get rid of the whole IO ECS deal
>>> altogether then.
>>>
>>> Now, I'm wondering whether we should kill it completely since I don't
>>> think anyone cares about numa node info being correct on K8, or? I'm
>>> specifically turning to our numascale friends who love to have a lot of
>>> nodes. :-)
>
> Maybe I did get you wrong, but IO ECS was introduced with fam10h and
> is not related to k8.
>
>> I think we need to be careful here as there are two unrelated topics
>> being discussed together.  What started this whole thread was the need
>> for sysfs related numa_node information with respect to PCI devices
>> (1).  Without patch 1, platforms with newer AMD CPUs end up having
>> '-1' numa_node values for all PCI devices.
>>
>> IO ECS has no bearing on patch 1, it only comes into play with patch 2
>> which is concerned with MMIO resource information when MCFG doesn't
>> exist.  For the particular issue I'm trying to get resolved, patch 2
>> is not needed.  However, since we have expended time and effort on
>> this subject, perhaps we should get this cleaned up while it has our
>> attention.
>>
>> I'm all for deleting as much of amd_bus.c as possible due to its
>> "perennial maintenance headache".  The obvious choices seem to be all,
>> or some combination, of:
>>    o removing IO ECS logic,
>>    o removing IO/MMIO logic (assuming MCFG issues were long enough ago
>> to no longer be a concern),
>>    o start deprecating amd_bus.c by adding logic to skip if BIOS >= 2015
>
> I don't see any reason for big changes actually. Just bind the IO ECS
> logic to fam10h (either with fam check or pci device depending on the
> implementation, xen's flavor would be pci). This is something stricter
> than 'if BIOS >= 2015'. It leaves code as it is which is maintainable.
>
> You implement the new logic for for newer families. No need for one
> implementation that fits all.
>
> -Robert
>
Actually, if ECS is needed by IBS, then wouldn't this still be needed 
for every family since 10h and later (except family11h).

Suravee
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