linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Kuppuswamy, Sathyanarayanan"  <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Jay Vosburgh <jay.vosburgh@canonical.com>, linux-pci@vger.kernel.org
Cc: Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH] PCI/ERR: Resolve regression in pcie_do_recovery
Date: Wed, 29 Apr 2020 18:15:33 -0700	[thread overview]
Message-ID: <18897ceb-2263-1101-ae43-918a66794e14@linux.intel.com> (raw)
In-Reply-To: <12115.1588207324@famine>



On 4/29/20 5:42 PM, Jay Vosburgh wrote:
> 	Commit 6d2c89441571 ("PCI/ERR: Update error status after
> reset_link()"), introduced a regression, as pcie_do_recovery will
> discard the status result from report_frozen_detected.  This can cause a
> failure to recover if _NEED_RESET is returned by report_frozen_detected
> and report_slot_reset is not invoked.
> 
> 	Such an event can be induced for testing purposes by reducing
> the Max_Payload_Size of a PCIe bridge to less than that of a device
> downstream from the bridge, and then initating I/O through the device,
> resulting in oversize transactions.  In the presence of DPC, this
> results in a containment event and attempted reset and recovery via
> pcie_do_recovery.  After 6d2c89441571 report_slot_reset is not invoked,
> and the device does not recover.

I think this issue is related to the issue discussed in following
thread (DPC non-hotplug support).

https://lkml.org/lkml/2020/3/28/328

If my assumption is correct, you are dealing with devices which are
not hotplug capable. If the devices are hotplug capable then you don't
need to proceed to report_slot_reset(), since hotplug handler will
remove/re-enumerate the devices correctly.

> 
> 	Inspection shows a similar path is plausible for a return of
> _CAN_RECOVER and the invocation of report_mmio_enabled.
> 
> 	Resolve this by preserving the result of report_frozen_detected if
> reset_link does not return _DISCONNECT.
> 
> Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
> Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
> 
> ---
>   drivers/pci/pcie/err.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index 14bb8f54723e..e4274562f3a0 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -164,10 +164,17 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>   
>   	pci_dbg(dev, "broadcast error_detected message\n");
>   	if (state == pci_channel_io_frozen) {
> +		pci_ers_result_t status2;
> +
>   		pci_walk_bus(bus, report_frozen_detected, &status);
> -		status = reset_link(dev);
> -		if (status != PCI_ERS_RESULT_RECOVERED) {
> +		/* preserve status from report_frozen_detected to
> +		 * insure report_mmio_enabled or report_slot_reset are
> +		 * invoked even if reset_link returns _RECOVERED.
> +		 */
> +		status2 = reset_link(dev);
> +		if (status2 != PCI_ERS_RESULT_RECOVERED) {
>   			pci_warn(dev, "link reset failed\n");
> +			status = status2;
>   			goto failed;
>   		}
>   	} else {
> 

  reply	other threads:[~2020-04-30  1:15 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-30  0:42 [PATCH] PCI/ERR: Resolve regression in pcie_do_recovery Jay Vosburgh
2020-04-30  1:15 ` Kuppuswamy, Sathyanarayanan [this message]
2020-04-30 19:35   ` Kuppuswamy, Sathyanarayanan
2020-04-30 20:41     ` Jay Vosburgh
2020-05-06 18:08       ` Jay Vosburgh
2020-05-09  6:35       ` Yicong Yang
2020-05-09 17:55         ` Kuppuswamy, Sathyanarayanan
2020-05-09  8:34 ` Yicong Yang
     [not found] <20200506203249.GA453633@bjorn-Precision-5520>
2020-05-07  0:56 ` Jay Vosburgh

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=18897ceb-2263-1101-ae43-918a66794e14@linux.intel.com \
    --to=sathyanarayanan.kuppuswamy@linux.intel.com \
    --cc=bhelgaas@google.com \
    --cc=jay.vosburgh@canonical.com \
    --cc=linux-pci@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).