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

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Message-ID: <20200727121726.000072a8@Huawei.com>
Date:   Mon, 27 Jul 2020 12:17:26 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Sean V Kelley <sean.v.kelley@...el.com>
CC:     <bhelgaas@...gle.com>, <rjw@...ysocki.net>, <ashok.raj@...nel.org>,
        <tony.luck@...el.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Qiuxu Zhuo <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?

> 
> 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);