linux-kernel - Re: [PATCH 1/2, pci] pci: Addition of PCI_DEV_FLAGS_QUIET_PCI

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Message-Id: <588ea850-2b28-2b7e-6e95-13d267f05cfa@linux.vnet.ibm.com>
Date:   Wed, 14 Mar 2018 15:09:28 -0300
From:   Desnes Augusto Nunes do Rosário 
        <desnesn@...ux.vnet.ibm.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci@...r.kernel.org,
        "open list:LINUX FOR POWERPC PA SEMI PWRFICIENT" 
        <linuxppc-dev@...ts.ozlabs.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, ruscur@...sell.cc,
        aik@...abs.ru, david@...son.dropbear.id.au,
        fbarrat@...ux.vnet.ibm.com, brking@...ux.vnet.ibm.com
Subject: Re: [PATCH 1/2, pci] pci: Addition of PCI_DEV_FLAGS_QUIET_PCI_REALIGN
 attribute to the PCI subsystem

Hello Andy,

On 03/14/2018 02:41 PM, Andy Shevchenko wrote:
> On Wed, Mar 14, 2018 at 6:34 PM, Desnes A. Nunes do Rosario
> <desnesn@...ux.vnet.ibm.com> wrote:
>> Add PCI_DEV_FLAGS_QUIET_PCI_REALIGN to pci_dev_flags and use it to
>> silent PCI realignment messages if the flag is turned on by a driver.
> 
> It doesn't explain "Why?"
> Why the driver needs that?

I have written down the reason on the cover letter, but I concur on 
creating a second version of the patch's comment. Basically, all PCI 
resources on powerpc are printing out expected realignment messages 
which are flooding the systems logs.

Perhaps this would be better?
---
"Some architectures such as powerpc has aligned all of its PCI resources 
to its PAGE_SIZE during boot, thus the system logs will be flooded by 
expected realignment messages, which can be interpreted as a false 
positive for total PCI failure on the system.

[root@...tem user]# dmesg | grep -i disabling
[    0.692270] pci 0000:00:00.0: Disabling memory decoding and releasing 
memory resources
[    0.692324] pci 0000:00:00.0: disabling bridge mem windows
[    0.729134] pci 0001:00:00.0: Disabling memory decoding and releasing 
memory resources
[    0.737352] pci 0001:00:00.0: disabling bridge mem windows
[    0.776295] pci 0002:00:00.0: Disabling memory decoding and releasing 
memory resources
[    0.784509] pci 0002:00:00.0: disabling bridge mem windows
... and goes on for all PCI devices ...

Thus, this patch adds PCI_DEV_FLAGS_NO_REALIGN_MSG to pci_dev_flags and 
uses it to silent PCI realignment messages if the flag is turned on by a 
driver.
"
---

> 
> Another approach is to increase level of the message. Would it be
> accepted by you (in case Bjorn agrees)?
> 
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -205,6 +205,8 @@ enum pci_dev_flags {
>>          PCI_DEV_FLAGS_NO_FLR_RESET = (__force pci_dev_flags_t) (1 << 10),
>>          /* Don't use Relaxed Ordering for TLPs directed at this device */
>>          PCI_DEV_FLAGS_NO_RELAXED_ORDERING = (__force pci_dev_flags_t) (1 << 11),
>> +       /* Silent PCI resource realignment messages */
>> +       PCI_DEV_FLAGS_QUIET_PCI_REALIGN = (__force pci_dev_flags_t) (1 << 12),
> 
> I would rather name it _NO_PCI_REALIGN_MSG

I concur on changing it to PCI_DEV_FLAGS_NO_REALIGN_MSG in a second 
version of the patchset.

> 
>>   };
> 

Thank you very much for your review,

-- 
Desnes A. Nunes do Rosário