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SubjectRe: [PATCH v6 07/10] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR
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On 27 Sep 2020, at 16:45, Bjorn Helgaas wrote:

> On Tue, Sep 22, 2020 at 02:38:56PM -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>
>> ---
>> drivers/pci/pcie/aer.c | 9 +++++----
>> drivers/pci/pcie/err.c | 38 ++++++++++++++++++++++++--------------
>> 2 files changed, 29 insertions(+), 18 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 5380ecc41506..a61a2518163a 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_bridge_walk - 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 +161,16 @@ 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_bridge_walk(struct pci_dev *bridge, int (*cb)(struct
>> pci_dev *, void *),
>> +static void pci_bridge_walk(struct pci_dev *bridge, struct pci_dev
>> *dev,
>> + int (*cb)(struct pci_dev *, void *),
>> void *userdata)
>> {
>> - if (bridge->subordinate)
>> + if (bridge && bridge->subordinate)
>
> I *guess* this means there's a possibility that bridge is NULL? And I
> guess that case is when pci_upstream_bridge(dev) in pcie_do_recovery()
> was NULL?
>
> I can't figure out what that means in practice. Oh, wait, I bet I
> know -- this is the non-native case where there's no OS-visible
> reporting device.

Yes, this is for the non-native case.

>
> We need some sort of comment because this is really not a top-of-mind
> situation unless you happen to be working on one of the few systems
> like that.

Will do.

>
> Not too sure this scenario is really a good fit for the
> pci_bridge_walk() model, but I think it's OK for now with a hint so we
> can remember this no RCEC, no Root Port model.

Understood.

>
>> 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 +200,24 @@ 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_bridge_walk(bridge, report_frozen_detected, &status);
>> + pci_bridge_walk(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).
>> + */
>> + if (bridge)
>> + reset_subordinate_devices(bridge);
>
> It's unfortunate to add yet another special case in this code, and I'm
> not thrilled about the one in aer_root_reset() either. It's just not
> obvious why they should be there. I'm sure if I spent 30 minutes
> decoding things, it would all make sense. Guess I'm just griping
> because I don't have a better suggestion.

I could also add some more detail here referencing the non-native case
where there may not even exist an RCEC. Aside from comments, I could
employ a descriptive flag such as “native_bridge”.

Thanks,

Sean

>
>> status = flr_on_rciep(dev);
>> if (status != PCI_ERS_RESULT_RECOVERED) {
>> pci_warn(dev, "function level reset failed\n");
>> @@ -219,13 +231,13 @@ pci_ers_result_t pcie_do_recovery(struct
>> pci_dev *dev,
>> }
>> }
>> } else {
>> - pci_bridge_walk(bridge, report_normal_detected, &status);
>> + pci_bridge_walk(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_bridge_walk(bridge, report_mmio_enabled, &status);
>> + pci_bridge_walk(bridge, dev, report_mmio_enabled, &status);
>> }
>>
>> if (status == PCI_ERS_RESULT_NEED_RESET) {
>> @@ -236,18 +248,16 @@ 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_bridge_walk(bridge, report_slot_reset, &status);
>> + pci_bridge_walk(bridge, dev, report_slot_reset, &status);
>> }
>>
>> if (status != PCI_ERS_RESULT_RECOVERED)
>> goto failed;
>>
>> pci_dbg(dev, "broadcast resume message\n");
>> - pci_bridge_walk(bridge, report_resume, &status);
>> + pci_bridge_walk(bridge, dev, report_resume, &status);
>>
>> - if (type == PCI_EXP_TYPE_ROOT_PORT ||
>> - type == PCI_EXP_TYPE_DOWNSTREAM ||
>> - type == PCI_EXP_TYPE_RC_EC) {
>> + if (bridge) {
>> if (pcie_aer_is_native(bridge))
>> pcie_clear_device_status(bridge);
>> pci_aer_clear_nonfatal_status(bridge);
>> --
>> 2.28.0
>>

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