Re: [PATCH V2 0/9] Add RCEC handling to PCI/AER

From: Sean V Kelley
Date: Wed Aug 05 2020 - 14:21:43 EST

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In reply to: Bjorn Helgaas: "Re: [PATCH V2 0/9] Add RCEC handling to PCI/AER"
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On 5 Aug 2020, at 11:00, Bjorn Helgaas wrote:

On Tue, Aug 04, 2020 at 12:40:43PM -0700, Sean V Kelley wrote:

From: Sean V Kelley <sean.v.kelley@xxxxxxxxxxxxxxx>

On the use of FLR on RCiEPs for the fatal case, still interested in more
feedback from the earlier discussion here [1]:

[1] https://lore.kernel.org/linux-pci/C21C050B-48B1-4429-B019-C81F3AB8E843@xxxxxxxxx/

There is also the question of the absence of an FLR for non-fatal error.
If the device driver tells us that it needs "PCI_ERS_RESULT_NEED_RESET" by
the callback report_normal_detected() then we should try FLR on the device
as well.

On the use of variables with RP centric names such as the attributes
dev_attr_aer_rootport_total_err_..., one concern is the ripple effect on code
churn due to renaming. Open to suggestions, but trying to co-habitate so to
speak RCECs with RPs in the same drivers has trade-offs.

Changes since v1 [2]:

- Make PME capability of RCEC discoverable in get_port_device_capability().
- Replace the check on bnr with <= lastbusn in pcie_walk_rcec().
- Fix comment header for pcie_walk_rcec().
- Fix comment header for pci_walk_dev_affected().
- Fix spurious newline.
- Add sanity checks on dev->rcec.
- Use pci_dbg() in place of pci_info() for discovered RCiEPs.
- Remove AER RCEC AP FOUND message (accidently left in previously).
- Remove the check for RC_END from set_device_error_reporting() since
only Ports and RCECs are being passed.
(Jonathan Cameron)
- Fix the return type for flr_on_rciep().
(reported by lkp on DEC Alpha arch.)

[1] https://lore.kernel.org/linux-pci/20200724172223.145608-1-sean.v.kelley@xxxxxxxxx/

Root Complex Event Collectors (RCEC) provide support for terminating error
and PME messages from Root Complex Integrated Endpoints (RCiEPs). An RCEC
resides on a Bus in the Root Complex. Multiple RCECs can in fact reside on
a single bus. An RCEC will explicitly declare supported RCiEPs through the
Root Complex Endpoint Association Extended Capability.

(See PCIe 5.0-1, sections 1.3.2.3 (RCiEP), and 7.9.10 (RCEC Ext. Cap.))

The kernel lacks handling for these RCECs and the error messages received
from their respective associated RCiEPs. More recently, a new CPU
interconnect, Compute eXpress Link (CXL) depends on RCEC capabilities for
purposes of error messaging from CXL 1.1 supported RCiEP devices.

DocLink: https://www.computeexpresslink.org/

This use case is not limited to CXL. Existing hardware today includes
support for RCECs, such as the Denverton microserver product
family. Future hardware will be forthcoming.

(See Intel Document, Order number: 33061-003US)

So services such as AER or PME could be associated with an RCEC driver.
In the case of CXL, if an RCiEP (i.e., CXL 1.1 device) is associated with a
platform's RCEC it shall signal PME and AER error conditions through that
RCEC.

Towards the above use cases, add the missing RCEC class and extend the
PCIe Root Port and service drivers to allow association of RCiEPs to their
respective parent RCEC and facilitate handling of terminating error and PME
messages.

AER Test Results:
1) Inject a correctable error to the RCiEP 0000:e9:00.0
Run ./aer_inject <a parameter file as below>:
AER
PCI_ID 0000:e9:00.0
COR_STATUS BAD_TLP
HEADER_LOG 0 1 2 3

Log:
[ 76.155963] pcieport 0000:e8:00.4: aer_inject: Injecting errors 00000040/00000000 into device 0000:e9:00.0
[ 76.166966] pcieport 0000:e8:00.4: AER: Corrected error received: 0000:e9:00.0
[ 76.175253] pci 0000:e9:00.0: PCIe Bus Error: severity=Corrected, type=Data Link Layer, (Receiver ID)
[ 76.185633] pci 0000:e9:00.0: device [8086:4940] error status/mask=00000040/00002000
[ 76.194604] pci 0000:e9:00.0: [ 6] BadTLP

If you remove the timestamps, there will be less distraction here. As
I'm sure you know, the 0/n cover letter text doesn't really go
anywhere except the email archives. If this is potentially useful in
the future, it should be in the actual patch commit logs.

Right, the intent is to show how it was tested. Understood.

2) Inject a non-fatal error to the RCiEP 0000:e8:01.0
Run ./aer_inject <a parameter file as below>:
AER
PCI_ID 0000:e8:01.0
UNCOR_STATUS COMP_ABORT
HEADER_LOG 0 1 2 3

I think maybe this could be written in a way that could be cut and
pasted?

Good point. Will do.

Log:
[ 117.791854] pcieport 0000:e8:00.4: aer_inject: Injecting errors 00000000/00008000 into device 0000:e8:01.0
[ 117.804244] pcieport 0000:e8:00.4: AER: Uncorrected (Non-Fatal) error received: 0000:e8:01.0
[ 117.814652] igen6_edac 0000:e8:01.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Completer ID)
[ 117.828511] igen6_edac 0000:e8:01.0: device [8086:0b25] error status/mask=00008000/00100000
[ 117.839189] igen6_edac 0000:e8:01.0: [15] CmpltAbrt
[ 117.847365] igen6_edac 0000:e8:01.0: AER: TLP Header: 00000000 00000001 00000002 00000003
[ 117.857775] igen6_edac 0000:e8:01.0: AER: device recovery successful

3) Inject a fatal error to the RCiEP 0000:ed:01.0
Run ./aer_inject <a parameter file as below>:
AER
PCI_ID 0000:ed:01.0
UNCOR_STATUS MALF_TLP
HEADER_LOG 0 1 2 3

Log:
[ 131.511623] pcieport 0000:ed:00.4: aer_inject: Injecting errors 00000000/00040000 into device 0000:ed:01.0
[ 131.523259] pcieport 0000:ed:00.4: AER: Uncorrected (Fatal) error received: 0000:ed:01.0
[ 131.533842] igen6_edac 0000:ed:01.0: AER: PCIe Bus Error: severity=Uncorrected (Fatal), type=Inaccessible, (Unregistered Agent ID)
[ 131.655618] igen6_edac 0000:ed:01.0: AER: device recovery successful

Jonathan Cameron (1):
PCI/AER: Extend AER error handling to RCECs

Qiuxu Zhuo (6):
pci_ids: Add class code and extended capability for RCEC
PCI: Extend Root Port Driver to support RCEC
PCI/portdrv: Add pcie_walk_rcec() to walk RCiEPs associated with RCEC
PCI/AER: Apply function level reset to RCiEP on fatal error
PCI: Add 'rcec' field to pci_dev for associated RCiEPs
PCI/AER: Add RCEC AER error injection support

Sean V Kelley (2):
PCI/AER: Add RCEC AER handling
PCI/PME: Add RCEC PME handling

drivers/pci/pcie/aer.c | 36 +++++++++----
drivers/pci/pcie/aer_inject.c | 5 +-
drivers/pci/pcie/err.c | 90 +++++++++++++++++++++++++++------
drivers/pci/pcie/pme.c | 15 ++++--
drivers/pci/pcie/portdrv.h | 2 +
drivers/pci/pcie/portdrv_core.c | 90 +++++++++++++++++++++++++++++++--
drivers/pci/pcie/portdrv_pci.c | 20 +++++++-
include/linux/pci.h | 3 ++
include/linux/pci_ids.h | 1 +
include/uapi/linux/pci_regs.h | 7 +++
10 files changed, 233 insertions(+), 36 deletions(-)

I always apply patches to topic branches based at my "master" branch
(typically -rc1, so currently v5.8-rc1, but will soon be v5.9-rc1).

If your series doesn't apply there (as this one doesn't), it saves me
time if you tell me where it does apply. I figured out that this
applies cleanly on top of my pci/error branch, which does make sense.

I'd actually *rather* have patches based on "master", even if I have
to resolve conflicts, because that gives me the flexibility to squash
in fixes and re-merge the topic branches.

Okay. Good to know as this time it was put on your pci branch. Will switch back to master.

Thanks,

Sean

Bjorn

Next message: Peilin Ye: "[Linux-kernel-mentees] [PATCH net] Bluetooth: Fix slab-out-of-bounds read in hci_le_direct_adv_report_evt()"
Previous message: Xianting Tian: "[PATCH] aio: use wait_for_completion_io() when waiting for completion of io"
In reply to: Bjorn Helgaas: "Re: [PATCH V2 0/9] Add RCEC handling to PCI/AER"
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