linux-kernel - Re: [PATCH v6 05/10] PCI/AER: Apply function level reset to RCiEP on fatal error

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Message-ID: <20200925215854.GA2460270@bjorn-Precision-5520>
Date:   Fri, 25 Sep 2020 16:58:54 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sean V Kelley <seanvk.dev@...gontracks.org>
Cc:     bhelgaas@...gle.com, Jonathan.Cameron@...wei.com,
        rafael.j.wysocki@...el.com, ashok.raj@...el.com,
        tony.luck@...el.com, sathyanarayanan.kuppuswamy@...el.com,
        qiuxu.zhuo@...el.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 05/10] PCI/AER: Apply function level reset to RCiEP on
 fatal error

On Tue, Sep 22, 2020 at 02:38:54PM -0700, Sean V Kelley 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.
> 
> 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 e575fa6cee63..5380ecc41506 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -169,6 +169,17 @@ static void pci_bridge_walk(struct pci_dev *bridge, int (*cb)(struct pci_dev *,
>  		cb(bridge, userdata);
>  }
>  
> +static pci_ers_result_t 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;
> +}

Either we reset the device or we didn't; there is no third option.

If I read it correctly, nothing in pcie_do_recovery() cares about the
difference between PCI_ERS_RESULT_NONE and PCI_ERS_RESULT_DISCONNECT.
The status does get returned, but only edr_handle_event() looks at it,
and it doesn't care about the difference either.

So I think this should just return PCI_ERS_RESULT_RECOVERED or
PCI_ERS_RESULT_DISCONNECT.

>  pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>  			pci_channel_state_t state,
>  			pci_ers_result_t (*reset_subordinate_devices)(struct pci_dev *pdev))
> @@ -195,15 +206,17 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>  	if (state == pci_channel_io_frozen) {
>  		pci_bridge_walk(bridge, report_frozen_detected, &status);
>  		if (type == PCI_EXP_TYPE_RC_END) {
> -			pci_warn(dev, "link reset not possible for RCiEP\n");
> -			status = PCI_ERS_RESULT_NONE;
> -			goto failed;
> -		}
> -
> -		status = reset_subordinate_devices(bridge);
> -		if (status != PCI_ERS_RESULT_RECOVERED) {
> -			pci_warn(dev, "subordinate device 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_subordinate_devices(bridge);
> +			if (status != PCI_ERS_RESULT_RECOVERED) {
> +				pci_warn(dev, "subordinate device reset failed\n");
> +				goto failed;
> +			}
>  		}
>  	} else {
>  		pci_bridge_walk(bridge, report_normal_detected, &status);
> -- 
> 2.28.0
>