linux-kernel - Re: [PATCH v8 1/2] PCI: pciehp: Ignore link events when there is a fatal error pending

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Date:   Mon, 20 Aug 2018 11:22:38 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Sinan Kaya <okaya@...nel.org>
Cc:     linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Oza Pawandeep <poza@...eaurora.org>,
        Keith Busch <keith.busch@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 1/2] PCI: pciehp: Ignore link events when there is a
 fatal error pending

On Fri, Aug 17, 2018 at 11:51:09PM -0700, Sinan Kaya wrote:
> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -222,9 +222,27 @@ void pciehp_handle_disable_request(struct slot *slot)
>  void pciehp_handle_presence_or_link_change(struct slot *slot, u32 events)
>  {
>  	struct controller *ctrl = slot->ctrl;
> +	struct pci_dev *pdev = ctrl->pcie->port;
>  	bool link_active;
>  	u8 present;
>  
> +	/* If a fatal error is pending, wait for AER or DPC to handle it. */
> +	if (pcie_fatal_error_pending(pdev)) {
> +		bool recovered;
> +
> +		recovered = pcie_wait_fatal_error_clear(pdev);
> +
> +		/* If the fatal error is gone and the link is up, return */
> +		if (recovered && pcie_wait_for_link(pdev, true)) {
> +			ctrl_info(ctrl, "Slot(%s): Ignoring Link event due to successful fatal error recovery\n",
> +				  slot_name(slot));
> +			return;
> +		}
> +
> +		ctrl_info(ctrl, "Slot(%s): Fatal error recovery failed for Link event, trying hotplug reset\n",
> +			  slot_name(slot));
> +	}
> +

This differs from v7 of the patch in that *any* fatal error, not just
a Surprise Link Down, results in pciehp waiting for the error to clear.

I'm wondering if that's safe:  Theoretically, the user might quickly
swap the card in the slot during, say, a Completion Timeout Error,
and with this patch pciehp would carry on as if nothing happened.

Thanks,

Lukas