Hi,
On 22 Jun 2020, at 4:44, Jonathan Cameron wrote:
Was previously: PCI/AER: Add partial initial supprot for RCiEPs using
RCEC or
firmware first.
Currently the kernel does not handle AER errors for Root Complex
integrated
End Points (RCiEPs)[0]. These devices sit on a root bus within the
Root Complex
(RC). AER handling is performed by a Root Complex Event Collector
(RCEC) [1]
which is a effectively a type of RCiEP on the same root bus.
This code will only perform the correct reset flow for the case where
there
is no need to take any actions on the RCEC because the firmware is
responsible for them. This is true where APEI [2] is used to report
the AER
errors via a GHES[v2] HEST entry [3] and relevant AER CPER record [4]
and Firmware
First handling is in use.
Right, in the case of the RCEC one identifies the RCiEPs by the RCiEP
bitmap as a part of the RCEC Associated Endpoint Extended Capabilities.
This ‘search’ so to speak would make use also of the RCEC Associated
Bus Numbers Register to associate the devices with an RCEC when not on
the same bus.
As there is no current RCEC driver support, it should not be possible
to get
to this code via any routes other than the one above. Hence
appropriate RCEC
handling can be added when the RCEC driver support is ready.
The error handling is different from a normal PCIe End Point because:
1) There is no downstream port above an RCiEP as these devices sit on
a root
bus.
2) In general, it makes little sense to reset other devices on on the
same
root bus. For error handling outside the of the root complex (RC)
an AER
error will indicate that all the topology below the physical link,
which
the error is related to, will need to be reset as they share a
common
path to the host. For an RCiEP there is no such defined shared
path
relationship with other elements on the root bus.
A new walk function, similar to pci_bus_walk is provided that takes a
pci_dev
instead of a bus. If that dev corresponds to a downstream port it
will walk
the subordinate bus of that downstream port. If the dev does not then
it
will call the function on that device alone. This function allows us
to
avoid adding special cases to the majority of the error handling.
Then in that case the callback could add the additional checks specific
to identifying the associated RCiEPs.
Open questions:
1. Are we better protecting against link reset for an RCiEP in here or
should we put the check in the link reset functions?
2. If we were to get a stupid firmware record with the relevant reset
flag
set to trigger a link reset, what is the correct response? For now
I
try to report that we haven't done anything and print a warning.
3. Naming of pci_walk_below_dev is rather unsatisfying. Any better
ideas?
4. pci_walk_below_dev is perhaps not of general utility. Shall I make
it local
in err.c? If not would a precursor patch for that be preferred?’
It depends. Is it intended as a drop in replacement where needed for
pci_walk_bus()? So in that case you are now passing the dev structure
and do the check for subordinate or is it intended as being specific to
say RCEC? With AER, one could either first check for RC_EC type before
using this one. Or one could just drop in replace (passing the dev
structure instead) and the call back performs the RCEC specific checks
when a device is encountered.
Testing has been performed via error injection on a QEMU platform as
that lets
me create a wide range of topologies and report errors at any chosen
location.
Currently I have no plans to upstream this injection support, but am
happy to
share if useful to others.
I’m experimenting with it in my RCEC code in AER and will give you
additional feedback.
Thanks,
Sean
[0] ACPI PCI Express Base Specification 4.0 1.3.2.3 Root Complex
Integrated
Endpoint Rules.
[1] ACPI PCI Express Base Specification 4.0 6.2 Error Signalling and
Logging
[2] ACPI Specification 6.3 Chapter 18 ACPI Platform Error Interface
(APEI)
[3] ACPI Sepcification 6.3 18.2.3.7 Generic Hardware Error Source
[4] UEFI Specification 2.8, N.2.7 PCI Express Error Section
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
Changes since v1:
* Separated from the largely unrelated fix so the two can move
forwards separately.
* Instead of separate path for RCiEP handling use the method suggested
by Bjorn
and Sathyanarayanan with an adjusted pci_bus_walk.
Thanks all for reviews of V1.
drivers/pci/bus.c | 28 ++++++++++++++++++++++++++++
drivers/pci/pcie/err.c | 29 +++++++++++++++++++----------
include/linux/pci.h | 2 ++
3 files changed, 49 insertions(+), 10 deletions(-)
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 8e40b3e6da77..7cbe1ed2db3d 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -411,6 +411,34 @@ void pci_walk_bus(struct pci_bus *top, int
(*cb)(struct pci_dev *, void *),
}
EXPORT_SYMBOL_GPL(pci_walk_bus);
+/** pci_walk_below_dev - walk devices below (or on) another device
+ * @dev device for which we should walk below, include device
when not a port.
+ * @cb callback to be called for each device found
+ * @userdata arbitrary pointer to be passed to callback.
+ *
+ * If the device provided is a port,
+ * walk the subordinate bus, including any bridged devices
+ * on buses under this bus. Call the provided callback
+ * on each device found.
+ *
+ * If the device provided hs no subordinate bus, call the provided
+ * callback on the device itself.
+ *
+ */
+void pci_walk_below_dev(struct pci_dev *dev, int (*cb)(struct pci_dev
*, void *),
+ void *userdata)
+{
+ struct pci_bus *bus;
+
+ if (dev->subordinate) {
+ bus = dev->subordinate;
+ pci_walk_bus(bus, cb, userdata);
+ } else {
+ cb(dev, userdata);
+ }
+}
+EXPORT_SYMBOL_GPL(pci_walk_below_dev);
+
struct pci_bus *pci_bus_get(struct pci_bus *bus)
{
if (bus)
diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index 14bb8f54723e..fa08b1cc3d96 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -151,33 +151,39 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev
*dev,
pci_ers_result_t (*reset_link)(struct pci_dev *pdev))
{
pci_ers_result_t status = PCI_ERS_RESULT_CAN_RECOVER;
- struct pci_bus *bus;
/*
* Error recovery runs on all subordinates of the first downstream
port.
* If the downstream port detected the error, it is cleared at the
end.
+ * For RCiEPs we should reset just the RCiEP itself.
*/
if (!(pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
- pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM))
+ pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
+ pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END))
dev = dev->bus->self;
- bus = dev->subordinate;
pci_dbg(dev, "broadcast error_detected message\n");
if (state == pci_channel_io_frozen) {
- pci_walk_bus(bus, report_frozen_detected, &status);
+ pci_walk_below_dev(dev, report_frozen_detected, &status);
+ if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
+ pci_warn(dev, "link reset not possible for RCiEP\n");
+ status = PCI_ERS_RESULT_NONE;
+ goto failed;
+ }
+
status = reset_link(dev);
if (status != PCI_ERS_RESULT_RECOVERED) {
pci_warn(dev, "link reset failed\n");
goto failed;
}
} else {
- pci_walk_bus(bus, report_normal_detected, &status);
+ pci_walk_below_dev(dev, report_normal_detected, &status);
}
if (status == PCI_ERS_RESULT_CAN_RECOVER) {
status = PCI_ERS_RESULT_RECOVERED;
pci_dbg(dev, "broadcast mmio_enabled message\n");
- pci_walk_bus(bus, report_mmio_enabled, &status);
+ pci_walk_below_dev(dev, report_mmio_enabled, &status);
}
if (status == PCI_ERS_RESULT_NEED_RESET) {
@@ -188,17 +194,20 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev
*dev,
*/
status = PCI_ERS_RESULT_RECOVERED;
pci_dbg(dev, "broadcast slot_reset message\n");
- pci_walk_bus(bus, report_slot_reset, &status);
+ pci_walk_below_dev(dev, report_slot_reset, &status);
}
if (status != PCI_ERS_RESULT_RECOVERED)
goto failed;
pci_dbg(dev, "broadcast resume message\n");
- pci_walk_bus(bus, report_resume, &status);
+ pci_walk_below_dev(dev, report_resume, &status);
- pci_aer_clear_device_status(dev);
- pci_aer_clear_nonfatal_status(dev);
+ if ((pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
+ pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM)) {
+ pci_aer_clear_device_status(dev);
+ pci_aer_clear_nonfatal_status(dev);
+ }
pci_info(dev, "device recovery successful\n");
return status;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c79d83304e52..538bf0a76d33 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1411,6 +1411,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct
pci_dev *dev, int max,
void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *,
void *),
void *userdata);
+void pci_walk_below_dev(struct pci_dev *dev, int (*cb)(struct pci_dev
*, void *),
+ void *userdata);
int pci_cfg_space_size(struct pci_dev *dev);
unsigned char pci_bus_max_busnr(struct pci_bus *bus);
void pci_setup_bridge(struct pci_bus *bus);
--
2.19.1
