From: "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Yicong Yang <yangyicong@hisilicon.com>, bhelgaas@google.com
Cc: jay.vosburgh@canonical.com, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org, ashok.raj@intel.com
Subject: Re: [PATCH v1 1/1] PCI/ERR: Handle fatal error recovery for non-hotplug capable devices
Date: Thu, 21 May 2020 12:31:33 -0700 [thread overview]
Message-ID: <d59e5312-9f0b-f6b2-042a-363022989b8f@linux.intel.com> (raw)
In-Reply-To: <8dd2233c-a636-59fa-4c6e-5da08556d09e@hisilicon.com>
On 5/21/20 3:58 AM, Yicong Yang wrote:
> On 2020/5/21 1:04, Kuppuswamy, Sathyanarayanan wrote:
>>
>>
>> On 5/20/20 1:28 AM, Yicong Yang wrote:
>>> On 2020/5/7 11:32, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>>
>>>> If there are non-hotplug capable devices connected to a given
>>>> port, then during the fatal error recovery(triggered by DPC or
>>>> AER), after calling reset_link() function, we cannot rely on
>>>> hotplug handler to detach and re-enumerate the device drivers
>>>> in the affected bus. Instead, we will have to let the error
>>>> recovery handler call report_slot_reset() for all devices in
>>>> the bus to notify about the reset operation. Although this is
>>>> only required for non hot-plug capable devices, doing it for
>>>> hotplug capable devices should not affect the functionality.
>>>>
>>>> Along with above issue, this fix also applicable to following
>>>> issue.
>>>>
>>>> Commit 6d2c89441571 ("PCI/ERR: Update error status after
>>>> reset_link()") added support to store status of reset_link()
>>>> call. Although this fixed the error recovery issue observed if
>>>> the initial value of error status is PCI_ERS_RESULT_DISCONNECT
>>>> or PCI_ERS_RESULT_NO_AER_DRIVER, it also discarded 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 initiating 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.
>>>>
>>>> [original patch is from jay.vosburgh@canonical.com]
>>>> [original patch link https://lore.kernel.org/linux-pci/18609.1588812972@famine/]
>>>> Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
>>>> Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
>>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>> ---
>>>> drivers/pci/pcie/err.c | 19 +++++++++++++++----
>>>> 1 file changed, 15 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>>>> index 14bb8f54723e..db80e1ecb2dc 100644
>>>> --- a/drivers/pci/pcie/err.c
>>>> +++ b/drivers/pci/pcie/err.c
>>>> @@ -165,13 +165,24 @@ 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_walk_bus(bus, report_frozen_detected, &status);
>>>> - status = reset_link(dev);
>>>> - if (status != PCI_ERS_RESULT_RECOVERED) {
>>>> + status = PCI_ERS_RESULT_NEED_RESET;
>>>> + } else {
>>>> + pci_walk_bus(bus, report_normal_detected, &status);
>>>> + }
>>>> +
>>>> + if (status == PCI_ERS_RESULT_NEED_RESET) {
>>>> + if (reset_link) {
>>>> + if (reset_link(dev) != PCI_ERS_RESULT_RECOVERED)
>>>
>>> we'll call reset_link() only if link is frozen. so it may have problem here.
>> you mean before this change right?
>> After this change, reset_link() will be called as long as status is
>> PCI_ERS_RESULT_NEED_RESET.
>
> Yes. I think we should reset the link only if the io is blocked as before. There's
> no reason to reset a normal link.
Currently, only AER and DPC driver uses pcie_do_recovery() call. So the
possible reset_link options are dpc_reset_link() and aer_root_reset().
In dpc_reset_link() case, the link is already disabled and hence we
don't need to do another reset. In case of aer_root_reset() it
uses pci_bus_error_reset() to reset the slot.
>
> Furthermore, PCI_ERS_RESULT_NEED_RESET means device driver requires a slot reset rather
> than a link reset, so it maybe improper to use it to judge whether a link reset is needed.
> We decide whether to do a link reset only by the io state.
>
> Thanks,
> Yicong
>
>
>>>
>>> Thanks,
>>> Yicong
>>>
>>>
>>>> + status = PCI_ERS_RESULT_DISCONNECT;
>>>> + } else {
>>>> + if (pci_bus_error_reset(dev))
>>>> + status = PCI_ERS_RESULT_DISCONNECT;
>>>> + }
>>>> +
>>>> + if (status == PCI_ERS_RESULT_DISCONNECT) {
>>>> pci_warn(dev, "link reset failed\n");
>>>> goto failed;
>>>> }
>>>> - } else {
>>>> - pci_walk_bus(bus, report_normal_detected, &status);
>>>> }
>>>> if (status == PCI_ERS_RESULT_CAN_RECOVER) {
>>>
>> .
>>
>
next prev parent reply other threads:[~2020-05-21 19:31 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200506203249.GA453633@bjorn-Precision-5520>
2020-05-07 0:56 ` [PATCH] PCI/ERR: Resolve regression in pcie_do_recovery Jay Vosburgh
2020-05-07 3:32 ` [PATCH v1 1/1] PCI/ERR: Handle fatal error recovery for non-hotplug capable devices sathyanarayanan.kuppuswamy
2020-05-12 19:20 ` Jay Vosburgh
2020-05-13 1:50 ` Yicong Yang
2020-05-13 22:44 ` Bjorn Helgaas
2020-05-14 20:36 ` Kuppuswamy, Sathyanarayanan
2020-05-20 8:28 ` Yicong Yang
2020-05-20 17:04 ` Kuppuswamy, Sathyanarayanan
2020-05-21 10:58 ` Yicong Yang
2020-05-21 19:31 ` Kuppuswamy, Sathyanarayanan [this message]
2020-05-22 2:56 ` Yicong Yang
2020-05-27 1:31 ` Kuppuswamy, Sathyanarayanan
2020-05-27 3:00 ` Oliver O'Halloran
2020-05-27 3:06 ` Kuppuswamy, Sathyanarayanan
2020-05-27 3:35 ` Oliver O'Halloran
2020-05-27 3:50 ` Yicong Yang
2020-05-27 4:04 ` Kuppuswamy, Sathyanarayanan
2020-05-27 6:41 ` Yicong Yang
2020-05-28 3:57 ` Kuppuswamy, Sathyanarayanan
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=d59e5312-9f0b-f6b2-042a-363022989b8f@linux.intel.com \
--to=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=ashok.raj@intel.com \
--cc=bhelgaas@google.com \
--cc=jay.vosburgh@canonical.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=yangyicong@hisilicon.com \
/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).