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SubjectRe: [PATCH v8 11/14] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR
Date
On 9 Oct 2020, at 11:34, Sean V Kelley wrote:

> On 9 Oct 2020, at 11:26, Sean V Kelley wrote:
>
>> 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
>
> Thinking more on this, you could still pass dev->rcec to the callback
> (eventually aer_root_reset()), but you won’t have the ability to
> handle the FLR there without the pointer to the RC_END. That’s why I
> suggested passing the RC_END and checking for its RC_EC in
> aer_root_reset() if you want to also handle FLR there too from below.

Where you get into trouble is that you don’t want to do anything in
the non-native case and shouldn’t be going to the callback. So this
would add complexity to aer_root_reset() for checking on dev->rcec ==
NULL…where before you never would have invoked
reset_subordinate_devices() in the non-native case.


>
> 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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