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SubjectRe: [PATCH 1/2, pci] pci: Addition of PCI_DEV_FLAGS_QUIET_PCI_REALIGN attribute to the PCI subsystem
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Hello Bjorn,

On 03/14/2018 03:06 PM, Bjorn Helgaas wrote:
> On Wed, Mar 14, 2018 at 01:34:54PM -0300, Desnes A. Nunes do Rosario 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.
>>
>> Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.vnet.ibm.com>
>> ---
>> drivers/pci/pci.c | 3 ++-
>> drivers/pci/setup-res.c | 3 ++-
>> include/linux/pci.h | 2 ++
>> 3 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 8c71d1a66cdd..be197c944e5f 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -5505,7 +5505,8 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
>> return;
>> }
>>
>> - pci_info(dev, "Disabling memory decoding and releasing memory resources\n");
>> + if (!(dev->dev_flags & PCI_DEV_FLAGS_QUIET_PCI_REALIGN))
>> + pci_info(dev, "Disabling memory decoding and releasing memory resources\n");
>> pci_read_config_word(dev, PCI_COMMAND, &command);
>> command &= ~PCI_COMMAND_MEMORY;
>> pci_write_config_word(dev, PCI_COMMAND, command);
>> diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
>> index 369d48d6c6f1..00a538def763 100644
>> --- a/drivers/pci/setup-res.c
>> +++ b/drivers/pci/setup-res.c
>> @@ -172,7 +172,8 @@ EXPORT_SYMBOL(pci_claim_resource);
>>
>> void pci_disable_bridge_window(struct pci_dev *dev)
>> {
>> - pci_info(dev, "disabling bridge mem windows\n");
>> + if (!(dev->dev_flags & PCI_DEV_FLAGS_QUIET_PCI_REALIGN))
>> + pci_info(dev, "disabling bridge mem windows\n");
>
> As far as I'm concerned, we can just remove these messages completely.
> I don't think there's any real value there.

After I found out that this was happening to all PCI devices on powerpc
due to the __weak
pcibios_default_alignment() interface (necessary for VFIO passthrough
and performance), I confess that this was my first approach to this
matter; however I couldn't vouch the need of these messages on other
architectures.

If there are no further concerns, I definitely prefer sending a second
version of this patch only eliminating these messages and attesting the
reason why.

Thank you very much for your review Bjorn,

--
Desnes A. Nunes do Rosário

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