linux-kernel - RE: [RFC PATCH 5/9] PCI/AER: Apply function level reset to RCiEP on fatal error

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Date:   Tue, 28 Jul 2020 13:27:14 +0000
From:   "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>
To:     'Jonathan Cameron' <Jonathan.Cameron@...wei.com>,
        "Kelley, Sean V" <sean.v.kelley@...el.com>
CC:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "ashok.raj@...nel.org" <ashok.raj@...nel.org>,
        "Luck, Tony" <tony.luck@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...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: [RFC PATCH 5/9] PCI/AER: Apply function level reset to RCiEP on
 fatal error

> From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Sent: Monday, July 27, 2020 7:17 PM
> To: Kelley, Sean V <sean.v.kelley@...el.com>
> Cc: bhelgaas@...gle.com; rjw@...ysocki.net; ashok.raj@...nel.org; Luck,
> Tony <tony.luck@...el.com>;
> sathyanarayanan.kuppuswamy@...ux.intel.com; linux-pci@...r.kernel.org;
> linux-kernel@...r.kernel.org; Zhuo, Qiuxu <qiuxu.zhuo@...el.com>
> Subject: Re: [RFC PATCH 5/9] PCI/AER: Apply function level reset to RCiEP
> on fatal error
> 
> On Fri, 24 Jul 2020 10:22:19 -0700
> Sean V Kelley <sean.v.kelley@...el.com> wrote:
> 
> > From: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
> >
> > Attempt to do function level reset for an RCiEP associated with an
> > RCEC device on fatal error.
> 
> I'd like to understand more on your reasoning for flr here.
> Is it simply that it is all we can do, or is there some basis in a spec
> somewhere?
> 

Yes. Though there isn't the link reset for the RCiEP here, I think we should still be able to reset the RCiEP via FLR on fatal error, if the RCiEP supports FLR.

-Qiuxu

> >
> > Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
> > ---
> >  drivers/pci/pcie/err.c | 31 ++++++++++++++++++++++---------
> >  1 file changed, 22 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c index
> > 044df004f20b..9b3ec94bdf1d 100644
> > --- a/drivers/pci/pcie/err.c
> > +++ b/drivers/pci/pcie/err.c
> > @@ -170,6 +170,17 @@ static void pci_walk_dev_affected(struct
> pci_dev *dev, int (*cb)(struct pci_dev
> >  	}
> >  }
> >
> > +static enum pci_channel_state flr_on_rciep(struct pci_dev *dev) {
> > +	if (!pcie_has_flr(dev))
> > +		return PCI_ERS_RESULT_NONE;
> > +
> > +	if (pcie_flr(dev))
> > +		return PCI_ERS_RESULT_DISCONNECT;
> > +
> > +	return PCI_ERS_RESULT_RECOVERED;
> > +}
> > +
> >  pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> >  			enum pci_channel_state state,
> >  			pci_ers_result_t (*reset_link)(struct pci_dev *pdev))
> @@ -191,15
> > +202,17 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> >  	if (state == pci_channel_io_frozen) {
> >  		pci_walk_dev_affected(dev, report_frozen_detected,
> &status);
> >  		if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
> > -			pci_warn(dev, "link reset not possible for RCiEP\n");
> > -			status = PCI_ERS_RESULT_NONE;
> > -			goto failed;
> > -		}
> > -
> > -		status = reset_link(dev);
> > -		if (status != PCI_ERS_RESULT_RECOVERED) {
> > -			pci_warn(dev, "link reset failed\n");
> > -			goto failed;
> > +			status = flr_on_rciep(dev);
> > +			if (status != PCI_ERS_RESULT_RECOVERED) {
> > +				pci_warn(dev, "function level reset failed\n");
> > +				goto failed;
> > +			}
> > +		} else {
> > +			status = reset_link(dev);
> > +			if (status != PCI_ERS_RESULT_RECOVERED) {
> > +				pci_warn(dev, "link reset failed\n");
> > +				goto failed;
> > +			}
> >  		}
> >  	} else {
> >  		pci_walk_dev_affected(dev, report_normal_detected,
> &status);
>