linux-kernel - Re: [RFC PATCH v4 3/7] PCI: Ignore resource_alignment if PCI_PROBE

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Message-ID: <56EA9682.5050600@linux.vnet.ibm.com>
Date:	Thu, 17 Mar 2016 19:35:30 +0800
From:	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-doc@...r.kernel.org, bhelgaas@...gle.com, corbet@....net,
	aik@...abs.ru, benh@...nel.crashing.org, paulus@...ba.org,
	mpe@...erman.id.au, warrier@...ux.vnet.ibm.com,
	zhong@...ux.vnet.ibm.com, nikunj@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH v4 3/7] PCI: Ignore resource_alignment if
 PCI_PROBE_ONLY was set

On 2016/3/17 0:31, Alex Williamson wrote:
> On Mon,  7 Mar 2016 15:48:34 +0800
> Yongji Xie <xyjxie@...ux.vnet.ibm.com> wrote:
>
>> The resource_alignment will releases memory resources
>> allocated by firmware so that kernel can reassign new
>> resources later on. But this will cause the problem
>> that no resources can be allocated by kernel if
>> PCI_PROBE_ONLY was set, e.g. on pSeries platform
>> because PCI_PROBE_ONLY force kernel to use firmware
>> setup and not to reassign any resources.
>>
>> To solve this problem, this patch ignores
>> resource_alignment if PCI_PROBE_ONLY was set.
>>
>> Signed-off-by: Yongji Xie <xyjxie@...ux.vnet.ibm.com>
>> ---
>>   Documentation/kernel-parameters.txt |    2 ++
>>   drivers/pci/probe.c                 |    3 ++-
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index d8b29ab..8028631 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -2922,6 +2922,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>>   				windows need to be expanded.
>>   				noresize: Don't change the resources' sizes when
>>   				reassigning alignment.
>> +				Note that this option will not work if
>> +				PCI_PROBE_ONLY is set.
> How would a user have any idea if this is set?

I found the PCI_PROBE_ONLY is set on pSeries, maple and
arm with "firmware" kernel parameter enabled.

So can we say: Note that this option will not work on pSeries,
maple and arm with "firmware" kernel parameter enabled?
Or do you have any suggestion?

Thanks,
Yongji Xie