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

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Message-ID: <20180314185508.GE179719@bhelgaas-glaptop.roam.corp.google.com>
Date:   Wed, 14 Mar 2018 13:55:08 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Desnes Augusto Nunes do Rosário 
        <desnesn@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, bhelgaas@...gle.com,
        benh@...nel.crashing.org, paulus@...ba.org, 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

On Wed, Mar 14, 2018 at 03:22:44PM -0300, Desnes Augusto Nunes do Rosário wrote:
> 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@...ux.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,

No problem, welcome to PCI, and I hope we see more of your work!