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SubjectRe: [PATCH v8 11/14] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR
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Hi Bjorn,

On 9 Oct 2020, at 10:57, Bjorn Helgaas wrote:

> On Fri, Oct 02, 2020 at 11:47:32AM -0700, Sean V Kelley wrote:
>> From: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
>>
>> When attempting error recovery for an RCiEP associated with an RCEC
>> device,
>> there needs to be a way to update the Root Error Status, the
>> Uncorrectable
>> Error Status and the Uncorrectable Error Severity of the parent RCEC.
>> In some non-native cases in which there is no OS visible device
>> associated with the RCiEP, there is nothing to act upon as the
>> firmware
>> is acting before the OS. So add handling for the linked 'rcec' in
>> AER/ERR
>> while taking into account non-native cases.
>>
>> Co-developed-by: Sean V Kelley <sean.v.kelley@intel.com>
>> Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> ---
>> drivers/pci/pcie/aer.c | 9 +++++----
>> drivers/pci/pcie/err.c | 39 ++++++++++++++++++++++++++++-----------
>> 2 files changed, 33 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index 65dff5f3457a..dccdba60b5d9 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -1358,17 +1358,18 @@ static int aer_probe(struct pcie_device *dev)
>> static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
>> {
>> int aer = dev->aer_cap;
>> + int rc = 0;
>> u32 reg32;
>> - int rc;
>> -
>>
>> /* Disable Root's interrupt in response to error messages */
>> pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
>> reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
>> pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
>>
>> - rc = pci_bus_error_reset(dev);
>> - pci_info(dev, "Root Port link has been reset\n");
>> + if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC) {
>> + rc = pci_bus_error_reset(dev);
>> + pci_info(dev, "Root Port link has been reset\n");
>> + }
>>
>> /* Clear Root Error Status */
>> pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &reg32);
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index 38abd7984996..956ad4c86d53 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -149,7 +149,8 @@ static int report_resume(struct pci_dev *dev,
>> void *data)
>> /**
>> * pci_walk_bridge - walk bridges potentially AER affected
>> * @bridge bridge which may be an RCEC with associated RCiEPs,
>> - * an RCiEP associated with an RCEC, or a Port.
>> + * or a Port.
>> + * @dev an RCiEP lacking an associated RCEC.
>> * @cb callback to be called for each device found
>> * @userdata arbitrary pointer to be passed to callback.
>> *
>> @@ -160,13 +161,20 @@ static int report_resume(struct pci_dev *dev,
>> void *data)
>> * If the device provided has no subordinate bus, call the provided
>> * callback on the device itself.
>> */
>> -static void pci_walk_bridge(struct pci_dev *bridge, int (*cb)(struct
>> pci_dev *, void *),
>> +static void pci_walk_bridge(struct pci_dev *bridge, struct pci_dev
>> *dev,
>> + int (*cb)(struct pci_dev *, void *),
>> void *userdata)
>> {
>> - if (bridge->subordinate)
>> + /*
>> + * In a non-native case where there is no OS-visible reporting
>> + * device the bridge will be NULL, i.e., no RCEC, no PORT.
>> + */
>> + if (bridge && bridge->subordinate)
>> pci_walk_bus(bridge->subordinate, cb, userdata);
>> - else
>> + else if (bridge)
>> cb(bridge, userdata);
>> + else
>> + cb(dev, userdata);
>> }
>>
>> static pci_ers_result_t flr_on_rciep(struct pci_dev *dev)
>> @@ -196,16 +204,25 @@ pci_ers_result_t pcie_do_recovery(struct
>> pci_dev *dev,
>> type = pci_pcie_type(dev);
>> if (type == PCI_EXP_TYPE_ROOT_PORT ||
>> type == PCI_EXP_TYPE_DOWNSTREAM ||
>> - type == PCI_EXP_TYPE_RC_EC ||
>> - type == PCI_EXP_TYPE_RC_END)
>> + type == PCI_EXP_TYPE_RC_EC)
>> bridge = dev;
>> + else if (type == PCI_EXP_TYPE_RC_END)
>> + bridge = dev->rcec;
>> else
>> bridge = pci_upstream_bridge(dev);
>>
>> pci_dbg(dev, "broadcast error_detected message\n");
>> if (state == pci_channel_io_frozen) {
>> - pci_walk_bridge(bridge, report_frozen_detected, &status);
>> + pci_walk_bridge(bridge, dev, report_frozen_detected, &status);
>> if (type == PCI_EXP_TYPE_RC_END) {
>> + /*
>> + * The callback only clears the Root Error Status
>> + * of the RCEC (see aer.c). Only perform this for the
>> + * native case, i.e., an RCEC is present.
>> + */
>> + if (bridge)
>> + reset_subordinate_devices(bridge);
>
> Help me understand this. There are lots of callbacks in this picture,
> but I guess this "callback only clears Root Error Status" must refer
> to aer_root_reset(), i.e., the reset_subordinate_devices pointer?

The ‘bridge’ in this case will always be dev->rcec, the event
collector for the associated RC_END. And that’s what’s being cleared
in aer.c via aer_root_reset() as the callback. It’s also being checked
for native/non-native here.

>
> Of course, the caller of pcie_do_recovery() supplied that pointer.
> And we can infer that it must be aer_root_reset(), not
> dpc_reset_link(), because RCECs and RCiEPs are not allowed to
> implement DPC.

Correct.

>
> I wish we didn't have either this assumption about what
> reset_subordinate_devices points to, or the assumption about what
> aer_root_reset() does. They both seem a little bit tenuous.

Agree. It’s the relationship between the RC_END and the RC_EC.

>
> We already made aer_root_reset() smart enough to check for RCECs. Can
> we put the FLR there, too? Then we wouldn't have this weird situation
> where reset_subordinate_devices() does a reset and clears error
> status, EXCEPT for this case where it only clears error status and we
> do the reset here?

We could add the smarts to aer_root_reset() to check for an RC_END in
that callback and perform the clear there on its RC_EC. We just
wouldn’t map ‘bridge’ to dev->rcec for RC_END in
pcie_do_recovery() which would simplify things.

Further, the FLR in the case of flr_on_rciep() below is specific to the
RCiEP itself. So it could be performed either in aer_root_reset() or
remain in the pcie_do_recovery().

That should work.

Sean


>
>> status = flr_on_rciep(dev);
>> if (status != PCI_ERS_RESULT_RECOVERED) {
>> pci_warn(dev, "function level reset failed\n");
>> @@ -219,13 +236,13 @@ pci_ers_result_t pcie_do_recovery(struct
>> pci_dev *dev,
>> }
>> }
>> } else {
>> - pci_walk_bridge(bridge, report_normal_detected, &status);
>> + pci_walk_bridge(bridge, 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_bridge(bridge, report_mmio_enabled, &status);
>> + pci_walk_bridge(bridge, dev, report_mmio_enabled, &status);
>> }
>>
>> if (status == PCI_ERS_RESULT_NEED_RESET) {
>> @@ -236,14 +253,14 @@ 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_bridge(bridge, report_slot_reset, &status);
>> + pci_walk_bridge(bridge, dev, report_slot_reset, &status);
>> }
>>
>> if (status != PCI_ERS_RESULT_RECOVERED)
>> goto failed;
>>
>> pci_dbg(dev, "broadcast resume message\n");
>> - pci_walk_bridge(bridge, report_resume, &status);
>> + pci_walk_bridge(bridge, dev, report_resume, &status);
>>
>> if (type == PCI_EXP_TYPE_ROOT_PORT ||
>> type == PCI_EXP_TYPE_DOWNSTREAM ||
>> --
>> 2.28.0
>>

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