Re: [PATCH v9 10/15] PCI/ERR: Limit AER resets in pcie_do_recovery()

[Sean V Kelley]

On 16 Oct 2020, at 10:22, Bjorn Helgaas wrote:

> On Thu, Oct 15, 2020 at 05:11:08PM -0700, Sean V Kelley wrote:
> > From: Sean V Kelley <sean.v.kelley@xxxxxxxxx>
> >
> > In some cases a bridge may not exist as the hardware controlling may 
> > be
> > handled only by firmware and so is not visible to the OS. This 
> > scenario is
> > also possible in future use cases involving non-native use of RCECs 
> > by
> > firmware.
> >
> > Explicitly apply conditional logic around these resets by limiting 
> > them to
> > Root Ports and Downstream Ports.
> >
> > Link: 
> > https://lore.kernel.org/r/20201002184735.1229220-8-seanvk.dev@xxxxxxxxxxxxxxxx
> > Signed-off-by: Sean V Kelley <sean.v.kelley@xxxxxxxxx>
> > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Acked-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > ---
> >  drivers/pci/pcie/err.c | 31 +++++++++++++++++++++++++------
> >  1 file changed, 25 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > index 8b53aecdb43d..7883c9791562 100644
> > --- a/drivers/pci/pcie/err.c
> > +++ b/drivers/pci/pcie/err.c
> > @@ -148,13 +148,17 @@ static int report_resume(struct pci_dev *dev, 
> > void *data)
> >
> >  /**
> >   * pci_walk_bridge - walk bridges potentially AER affected
> > - * @bridge:	bridge which may be a Port
> > + * @bridge:	bridge which may be a Port, an RCEC with associated 
> > RCiEPs,
> > + *		or an RCiEP associated with an RCEC
> >   * @cb:		callback to be called for each device found
> >   * @userdata:	arbitrary pointer to be passed to callback
> >   *
> >   * If the device provided is a bridge, walk the subordinate bus, 
> > including
> >   * any bridged devices on buses under this bus.  Call the provided 
> > callback
> >   * on each device found.
> > + *
> > + * If the device provided has no subordinate bus, call the callback 
> > on the
> > + * device itself.
> >   */
> >  static void pci_walk_bridge(struct pci_dev *bridge,
> >  			    int (*cb)(struct pci_dev *, void *),
> > @@ -162,6 +166,8 @@ static void pci_walk_bridge(struct pci_dev 
> > *bridge,
> >  {
> >  	if (bridge->subordinate)
> >  		pci_walk_bus(bridge->subordinate, cb, userdata);
> > +	else
> > +		cb(bridge, userdata);
>
> Looks like *this* is the patch where the "no subordinate bus" case
> becomes possible?  If you agree, I can just move the test here, no
> need to repost.

Agree, this is the patch that the check is needed as we are opening 
things up for walking RC_ECs and RC_ENDs as below.

Sean


> >  }
> >
> >  pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> > @@ -174,10 +180,13 @@ pci_ers_result_t pcie_do_recovery(struct 
> > pci_dev *dev,
> >
> >  	/*
> >  	 * Error recovery runs on all subordinates of the bridge.  If the
> > -	 * bridge detected the error, it is cleared at the end.
> > +	 * bridge detected the error, it is cleared at the end.  For RCiEPs
> > +	 * we should reset just the RCiEP itself.
> >  	 */
> >  	if (type == PCI_EXP_TYPE_ROOT_PORT ||
> > -	    type == PCI_EXP_TYPE_DOWNSTREAM)
> > +	    type == PCI_EXP_TYPE_DOWNSTREAM ||
> > +	    type == PCI_EXP_TYPE_RC_EC ||
> > +	    type == PCI_EXP_TYPE_RC_END)
> >  		bridge = dev;
> >  	else
> >  		bridge = pci_upstream_bridge(dev);
> > @@ -185,6 +194,12 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev 
> > *dev,
> >  	pci_dbg(bridge, "broadcast error_detected message\n");
> >  	if (state == pci_channel_io_frozen) {
> >  		pci_walk_bridge(bridge, report_frozen_detected, &status);
> > +		if (type == PCI_EXP_TYPE_RC_END) {
> > +			pci_warn(dev, "subordinate device reset not possible for 
> > RCiEP\n");
> > +			status = PCI_ERS_RESULT_NONE;
> > +			goto failed;
> > +		}
> > +
> >  		status = reset_subordinates(bridge);
> >  		if (status != PCI_ERS_RESULT_RECOVERED) {
> >  			pci_warn(bridge, "subordinate device reset failed\n");
> > @@ -217,9 +232,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev 
> > *dev,
> >  	pci_dbg(bridge, "broadcast resume message\n");
> >  	pci_walk_bridge(bridge, report_resume, &status);
> >
> > -	if (pcie_aer_is_native(bridge))
> > -		pcie_clear_device_status(bridge);
> > -	pci_aer_clear_nonfatal_status(bridge);
> > +	if (type == PCI_EXP_TYPE_ROOT_PORT ||
> > +	    type == PCI_EXP_TYPE_DOWNSTREAM ||
> > +	    type == PCI_EXP_TYPE_RC_EC) {
> > +		if (pcie_aer_is_native(bridge))
> > +			pcie_clear_device_status(bridge);
> > +		pci_aer_clear_nonfatal_status(bridge);
> > +	}
> >  	pci_info(bridge, "device recovery successful\n");
> >  	return status;
> >
> > --
> > 2.28.0