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Date: Fri, 09 Oct 2020 11:34:01 -0700
From: "Sean V Kelley" <sean.v.kelley@...el.com>
To: "Bjorn Helgaas" <helgaas@...nel.org>
Cc: "Sean V Kelley" <seanvk.dev@...gontracks.org>, bhelgaas@...gle.com,
Jonathan.Cameron@...wei.com, rafael.j.wysocki@...el.com,
ashok.raj@...el.com, tony.luck@...el.com,
sathyanarayanan.kuppuswamy@...el.com, qiuxu.zhuo@...el.com,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 11/14] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR
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@...el.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@...el.com>
>>> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
>>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.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, ®32);
>>> 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, ®32);
>>> 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.
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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