linux-kernel - Re: [PATCH v2] PCIe AER: report uncorrectable errors only to the functions that logged the errors

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Message-ID: <20170831200344.GF18250@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 31 Aug 2017 15:03:44 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Gabriele Paoloni <gabriele.paoloni@...wei.com>
Cc:     linuxarm@...wei.com, liudongdong3@...wei.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCIe AER: report uncorrectable errors only to the
 functions that logged the errors

On Fri, Aug 18, 2017 at 12:02:21PM +0100, Gabriele Paoloni wrote:
> Currently if an uncorrectable error is reported by an EP the AER
> driver walks over all the devices connected to the upstream port
> bus and in turns call the report_error_detected() callback.
> If any of the devices connected to the bus does not implement
> dev->driver->err_handler->error_detected() do_recovery() will fail
> leaving all the bus hierarchy devices unrecovered.
> 
> However for non fatal errors the PCIe link should not be considered
> compromised, therefore it makes sense to report the error only to
> all the functions that logged an error.

Can you include a pointer to the relevant part of the spec here?

> This patch implements this new behaviour for non fatal errors.
> 
> Signed-off-by: Gabriele Paoloni <gabriele.paoloni@...wei.com>
> Signed-off-by: Dongdong Liu <liudongdong3@...wei.com>
> ---
> Changes from v1:
>    - now errors are reported only to the fucntions that logged the error
>      instead of all the functions in the same device.
>    - the patch subject has changed to match the new implementation
> ---
>  drivers/pci/pcie/aer/aerdrv_core.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
> index b1303b3..057465ad 100644
> --- a/drivers/pci/pcie/aer/aerdrv_core.c
> +++ b/drivers/pci/pcie/aer/aerdrv_core.c
> @@ -390,7 +390,14 @@ static pci_ers_result_t broadcast_error_message(struct pci_dev *dev,
>  		 * If the error is reported by an end point, we think this
>  		 * error is related to the upstream link of the end point.
>  		 */
> -		pci_walk_bus(dev->bus, cb, &result_data);
> +		if (state == pci_channel_io_normal)
> +			/*
> +			 * the error is non fatal so the bus is ok, just invoke
> +			 * the callback for the function that logged the error.
> +			 */
> +			cb(dev, &result_data);
> +		else
> +			pci_walk_bus(dev->bus, cb, &result_data);

I think the concept of this change makes sense, but I don't like the
implicit connection of PCI_ERR_ROOT_UNCOR_RCV -> AER_NONFATAL ->
pci_channel_io_normal.  That makes it harder than it should be to read
the code.

What would you think of changing the signature of do_recovery() and
broadcast_error_message() so they take the struct aer_err_info pointer
instead of just the severity and pci_channel_state?  Then we could
check directly for AER_NONFATAL here.

Bjorn