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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 14:30, Bjorn Helgaas wrote:

> On Fri, Oct 09, 2020 at 12:57:45PM -0500, 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?
>>
>> 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.
>>
>> 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.
>>
>> 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?
>
> Just as an example to make this concrete. Doesn't even compile.

Okay, I tried something similar. Comments below:

>
>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index d6927e6535e5..e389db7cbba6 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1372,28 +1372,45 @@ 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 type = pci_pcie_type(dev);
> + struct pci_dev *root;
> + int aer = 0;
> int rc = 0;
> u32 reg32;
>
> - /* 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);
> + if (type == PCI_EXP_TYPE_RC_END)
> + root = dev->rcec;
> + else
> + root = dev;
> +
> + if (root)
> + aer = root->aer_cap;

Except here dev->rcec may be NULL for the non-native case. So I had a
goto label to bypass what follows. I left the FLR in err.c.


>
> - if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC) {
> + if (aer) {
> + /* Disable Root's interrupt in response to error messages */
> + pci_read_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, &reg32);
> + reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
> + pci_write_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, reg32);
> + }
> +
> + if (type == PCI_EXP_TYPE_RC_EC || type == PCI_EXP_TYPE_RC_END) {
> + rc = flr_on_rciep(dev);
> + pci_info(dev, "has been reset (%d)\n", rc);
> + } else {
> rc = pci_bus_error_reset(dev);
> - pci_info(dev, "Root Port link has been reset\n");
> + pci_info(dev, "Root Port link has been reset (%d)\n", rc);
> }
>
> - /* Clear Root Error Status */
> - pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &reg32);
> - pci_write_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, reg32);
> + if (aer) {
> + /* Clear Root Error Status */
> + pci_read_config_dword(root, aer + PCI_ERR_ROOT_STATUS, &reg32);
> + pci_write_config_dword(root, aer + PCI_ERR_ROOT_STATUS, reg32);
>
> - /* Enable Root Port'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);
> + /* Enable Root Port's interrupt in response to error messages */
> + pci_read_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, &reg32);
> + reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
> + pci_write_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, reg32);
> + }
>
> return rc ? PCI_ERS_RESULT_DISCONNECT : PCI_ERS_RESULT_RECOVERED;
> }
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index 79ae1356141d..08976034a89c 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -203,36 +203,19 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev
> *dev,
> */
> if (type == PCI_EXP_TYPE_ROOT_PORT ||
> type == PCI_EXP_TYPE_DOWNSTREAM ||
> - type == PCI_EXP_TYPE_RC_EC)
> + type == PCI_EXP_TYPE_RC_EC ||
> + type == PCI_EXP_TYPE_RC_END)
> bridge = dev;
> - else if (type == PCI_EXP_TYPE_RC_END)
> - bridge = dev->rcec;
> else
> bridge = pci_upstream_bridge(dev);
>
> pci_dbg(bridge, "broadcast error_detected message\n");
> if (state == pci_channel_io_frozen) {
> pci_walk_bridge(bridge, dev, report_frozen_detected, &status);

We’d need to walk back the dev addition to the pci_walk_bridge() and
revert to prior to the checks on dev->rcec.

> - 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_subordinates(bridge);
> -
> - status = flr_on_rciep(dev);
> - if (status != PCI_ERS_RESULT_RECOVERED) {
> - pci_warn(dev, "Function Level Reset failed\n");
> - goto failed;
> - }
> - } else {
> - status = reset_subordinates(bridge);
> - if (status != PCI_ERS_RESULT_RECOVERED) {
> - pci_warn(dev, "subordinate device reset failed\n");
> - goto failed;
> - }
> + status = reset_subordinates(bridge);
> + if (status != PCI_ERS_RESULT_RECOVERED) {
> + pci_warn(bridge, "subordinate device reset failed\n");
> + goto failed;
> }
> } else {
> pci_walk_bridge(bridge, dev, report_normal_detected, &status);

So this is what I experimented with for the most part but with the
changes that I highlighted - addressing non-native case in the callback
and also in the bridge walk.

I can test it out.

Thanks,

Sean

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