linux-kernel - Re: [PATCH v3] PCI/AER: Enable reporting for ports enumerated after AER driver registration

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Message-ID: <20181018204915.GK5906@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 18 Oct 2018 15:49:16 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Keith Busch <keith.busch@...el.com>
Cc:     "Derrick, Jonathan" <jonathan.derrick@...el.com>,
        Dongdong Liu <liudongdong3@...wei.com>,
        Sinan Kaya <okaya@...nel.org>,
        Oza Pawandeep <poza@...eaurora.org>,
        Matthew Wilcox <willy@...radead.org>,
        Lukas Wunner <lukas@...ner.de>, Christoph Hellwig <hch@....de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] PCI/AER: Enable reporting for ports enumerated after
 AER driver registration

On Thu, Oct 11, 2018 at 09:57:16AM -0600, Keith Busch wrote:
> On Thu, Oct 11, 2018 at 08:26:18AM -0700, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@...gle.com>
> > 
> > Previously we enabled AER error reporting only for Switch Ports that were
> > enumerated prior to registering the AER service driver.  Switch Ports
> > enumerated after AER driver registration were left with error reporting
> > disabled.
> > 
> > A common order, which works correctly, is that we enumerate devices before
> > registering portdrv and the AER driver:
> > 
> >   - Enumerate all the devices at boot-time
> > 
> >   - Register portdrv and bind it to all Root Ports and Switch Ports, which
> >     disables error reporting for these Ports
> > 
> >   - Register AER service driver and bind it to all Root Ports, which
> >     enables error reporting for the Root Ports and any Switch Ports below
> >     them
> > 
> > But if we enumerate devices *after* registering portdrv and the AER driver,
> > e.g., if a host bridge driver is loaded as a module, error reporting is not
> > enabled correctly:
> > 
> >   - Register portdrv and AER driver (this happens at boot-time)
> > 
> >   - Enumerate a Root Port
> > 
> >   - Bind portdrv to Root Port, disabling its error reporting
> > 
> >   - Bind AER service driver to Root Port, enabling error reporting for it
> >     and its children (there are no children, since we haven't enumerated
> >     them yet)
> > 
> >   - Enumerate Switch Port below the Root Port
> > 
> >   - Bind portdrv to Switch Port, disabling its error reporting
> > 
> >   - AER service driver doesn't bind to Switch Ports, so error reporting
> >     remains disabled
> > 
> > Hot-adding a Switch fails similarly: error reporting is enabled correctly
> > for the Root Port, but when the Switch is enumerated, the AER service
> > driver doesn't claim it, so there's nothing to enable error reporting for
> > the Switch Ports.
> > 
> > Change the AER service driver so it binds to *all* PCIe Ports, including
> > Switch Upstream and Downstream Ports.  Enable AER error reporting for all
> > these Ports, but not for any children.
> > 
> > Link: https://lore.kernel.org/linux-pci/1536085989-2956-1-git-send-email-jonathan.derrick@intel.com
> > Based-on-patch-by: Jon Derrick <jonathan.derrick@...el.com>
> > Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > ---
> >  drivers/pci/pcie/aer.c |   16 +++++++++-------
> >  1 file changed, 9 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index 90b53abf621d..c40c6607849b 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -1316,12 +1316,6 @@ static void aer_enable_rootport(struct aer_rpc *rpc)
> >  	pci_read_config_dword(pdev, aer_pos + PCI_ERR_UNCOR_STATUS, &reg32);
> >  	pci_write_config_dword(pdev, aer_pos + PCI_ERR_UNCOR_STATUS, reg32);
> >  
> > -	/*
> > -	 * Enable error reporting for the root port device and downstream port
> > -	 * devices.
> > -	 */
> > -	set_downstream_devices_error_reporting(pdev, true);
> > -
> >  	/* Enable Root Port's interrupt in response to error messages */
> >  	pci_read_config_dword(pdev, aer_pos + PCI_ERR_ROOT_COMMAND, &reg32);
> >  	reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
> > @@ -1378,10 +1372,17 @@ static void aer_remove(struct pcie_device *dev)
> >   */
> >  static int aer_probe(struct pcie_device *dev)
> >  {
> > +	struct pci_dev *pdev = dev->port;
> > +	int type = pci_pcie_type(pdev);
> >  	int status;
> >  	struct aer_rpc *rpc;
> >  	struct device *device = &dev->device;
> >  
> > +	if (type == PCI_EXP_TYPE_UPSTREAM || type == PCI_EXP_TYPE_DOWNSTREAM) {
> > +		pci_enable_pcie_error_reporting(pdev);
> > +		return 0;
> > +	}
> 
> I think we need to either return an error in this case so that the
> pcie_device won't be eligable for the .remove() callback, or add a
> similiar type check in aer_remove().

Indeed, thanks!  I think a check in aer_remove() seems nicer.  It doesn't
seem right to return an error here, since everything is working correctly.

Bjorn