Date:   Fri, 4 Dec 2020 17:17:58 +0000
From:   "Kelley, Sean V" <sean.v.kelley@...el.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "xerces.zhao@...il.com" <xerces.zhao@...il.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@...el.com>,
        "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        "Linux List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 12/15] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR

Hi Bjorn,

> On Dec 3, 2020, at 4:01 PM, Bjorn Helgaas <helgaas@...nel.org> wrote:
> 
> On Thu, Dec 03, 2020 at 12:51:40AM +0000, Kelley, Sean V wrote:
>>> On Dec 2, 2020, at 3:44 PM, Bjorn Helgaas <helgaas@...nel.org> wrote:
>>> On Fri, Nov 20, 2020 at 04:10:33PM -0800, 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.
>>>> 
>>>> 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>
>>>> Link: https://lore.kernel.org/r/20201002184735.1229220-12-seanvk.dev@oregontracks.org
>>>> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
>>>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>>>> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
>>>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>>>> ---
>>>> drivers/pci/pcie/aer.c | 46 +++++++++++++++++++++++++++++++-----------
>>>> drivers/pci/pcie/err.c | 20 +++++++++---------
>>>> 2 files changed, 44 insertions(+), 22 deletions(-)
>>>> 
>>>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>>>> index 0ba0b47ae751..51389a6ee4ca 100644
>>>> --- a/drivers/pci/pcie/aer.c
>>>> +++ b/drivers/pci/pcie/aer.c
>>>> @@ -1358,29 +1358,51 @@ 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;
>>>> -	int rc;
>>>> 
>>>> -	if (pcie_aer_is_native(dev)) {
>>>> +	if (type == PCI_EXP_TYPE_RC_END)
>>>> +		/*
>>>> +		 * The reset should only clear the Root Error Status
>>>> +		 * of the RCEC. Only perform this for the
>>>> +		 * native case, i.e., an RCEC is present.
>>>> +		 */
>>>> +		root = dev->rcec;
>>>> +	else
>>>> +		root = dev;
>>>> +
>>>> +	if (root)
>>>> +		aer = dev->aer_cap;
>>>> +
>>>> +	if ((aer) && pcie_aer_is_native(dev)) {
>>>> 		/* Disable Root's interrupt in response to error messages */
>>>> -		pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
>>>> +		pci_read_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, &reg32);
>>>> 		reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
>>>> -		pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
>>>> +		pci_write_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, reg32);
>>>> 	}
>>>> 
>>>> -	rc = pci_bus_error_reset(dev);
>>>> -	pci_info(dev, "Root Port link has been reset (%d)\n", rc);
>>>> +	if (type == PCI_EXP_TYPE_RC_EC || type == PCI_EXP_TYPE_RC_END) {
>>>> +		if (pcie_has_flr(dev)) {
>>>> +			rc = pcie_flr(dev);
>>>> +			pci_info(dev, "has been reset (%d)\n", rc);
>>> 
>>> Maybe:
>>> 
>>> +             } else {
>>> +                     rc = -ENOTTY;
>>> +                     pci_info(dev, "not reset (no FLR support)\n");
>>> 
>>> Or do we want to pretend the device was reset and return
>>> PCI_ERS_RESULT_RECOVERED?
>> 
>> We are currently doing the latter now with the default of rc = 0
>> above and so  I’m not sure the extra detail here on the absence of
>> FLR support is of value.
> 
> So to make sure I understand the proposal here, for RCECs and RCiEPs
> that don't support FLR, you're saying you want to continue silently
> and return PCI_ERS_RESULT_RECOVERED and let the drivers assume their
> device was reset when it was not?

The setting of the  ‘rc’  on the FLR support is  fine to add to the else condition.
I had simply recalled in earlier discussion that pcie_has_flr() was needed due to quirky
behavior in some hardware and so was not sure that detail of having or not having flr was in fact
consitent/accurate.

> 
>>>> +	} else {
>>>> +		rc = pci_bus_error_reset(dev);
>>>> +		pci_info(dev, "Root Port link has been reset (%d)\n", rc);
>>>> +	}
>>>> 
>>>> -	if (pcie_aer_is_native(dev)) {
>>>> +	if ((aer) && pcie_aer_is_native(dev)) {
>>>> 		/* 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);
>>>> +		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);
>>>> +		pci_read_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, &reg32);
>>>> 		reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
>>>> -		pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
>>>> +		pci_write_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, reg32);
>>>> 	}
>>>> 
>>>> 	return rc ? PCI_ERS_RESULT_DISCONNECT : PCI_ERS_RESULT_RECOVERED;
> 
>>>> @@ -164,8 +164,14 @@ static void pci_walk_bridge(struct pci_dev *bridge,
>>>> 			    int (*cb)(struct pci_dev *, void *),
>>>> 			    void *userdata)
>>>> {
>>>> +	/*
>>>> +	 * In a non-native case where there is no OS-visible reporting
>>>> +	 * device the bridge will be NULL, i.e., no RCEC, no Downstream Port.
>>> 
>>> I don't quite understand this comment.  I see that in the non-native
>>> case, the reporting device may not be OS-visible.  But I don't
>>> understand why the comment is *here*.
>>> 
>>> If "bridge" can be NULL here, we should test that before dereferencing
>>> "bridge->subordinate".
>> 
>> Wrongly worded.  The subordinate may be NULL or the associated RCEC
>> may be NULL, not the “bridge”.  However, per below, we should not be
>> trying to call report_frozen_detected(), report_mmio_enabled() via
>> the associated RCEC’s driver, but rather the CB for the RCiEP
>> itself.
> 
> OK, so if we want a comment here, I assume it would be along the lines
> of:
> 
>  If "bridge" has no subordinate bus, it's an RCEC or an RCiEP.  In
>  either of those cases, we want to call the callback on "bridge"
>  itself.
> 

Correct.

>> Going back to this conversation,
>> 
>> https://lore.kernel.org/linux-pci/20201016172210.GA86168@bjorn-Precision-5520/
>> 
>> "Looks like *this* is the patch where the "no subordinate bus" case
>> becomes possible?  If you agree, I can just move the test here, no
>> need to repost.”
>> 
>> It is actually the case we are only dealing with the absence of a
>> subordinate bus.
>> 
>>>> 	if (bridge->subordinate)
>>>> 		pci_walk_bus(bridge->subordinate, cb, userdata);
>>>> +	else if (bridge->rcec)
>>>> +		cb(bridge->rcec, userdata);
>>> 
>>> And I don't understand what's going on here.  In this case, I *think*
>>> "bridge" is an RCiEP and "bridge->rcec" is the related RCEC, so it
>>> looks like we'll call report_frozen_detected(), report_mmio_enabled(),
>>> etc for the RCEC driver.  I would think we'd want the RCiEP driver.
>> 
>> Indeed, the bridge->rcec here is the dev->rcec in which the dev is
>> the RCiEP.
>> 
>> And we don’t need that conditional here, it should just hit the
>> device driver’s routines.
> 
> So IIUC, the code would be:
> 
>  if (bridge->subordinate)
>    pci_walk_bus(bridge->subordinate, cb, userdata);
>  else
>    cb(bridge, userdata);    /* RCEC or RCiEP */
> 
> Right?

Right, as before.

> 
> I pushed a pci/err branch
> (https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=pci/err)
> with some tweaks in these areas.  Diff from your v12 posting appended
> below.  I split the RCEC/RCiEP error recovery pieces up a little bit
> differently than in your posting.  Let me know if you see anything
> that should be changed.  I dropped one of Jonathan's
> reviewed/tested-by but probably should have dropped others to avoid
> putting words in his mouth.

Thanks very much for doing this update.  It looks good to me.

> 
> Not sure we're completely done, but we'll get there yet.  I definitely
> want to make sure this happens this cycle.

I’ll retest today.

Thanks,

Sean


> 
> Bjorn
> 
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index b86a92494345..4aa118edde35 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1366,33 +1366,38 @@ static int aer_probe(struct pcie_device *dev)
> }
> 
> /**
> - * aer_root_reset - reset link on Root Port
> - * @dev: pointer to Root Port's pci_dev data structure
> + * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
> + * @dev: pointer to Root Port, RCEC, or RCiEP
>  *
> - * Invoked by Port Bus driver when performing link reset at Root Port.
> + * Invoked by Port Bus driver when performing reset.
>  */
> static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
> {
> 	int type = pci_pcie_type(dev);
> 	struct pci_dev *root;
> -	int aer = 0;
> -	int rc = 0;
> +	int aer;
> +	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
> 	u32 reg32;
> +	int rc;
> 
> +	/*
> +	 * Only Root Ports and RCECs have AER Root Command and Root Status
> +	 * registers.  If "dev" is an RCiEP, the relevant registers are in
> +	 * the RCEC.
> +	 */
> 	if (type == PCI_EXP_TYPE_RC_END)
> -		/*
> -		 * The reset should only clear the Root Error Status
> -		 * of the RCEC. Only perform this for the
> -		 * native case, i.e., an RCEC is present.
> -		 */
> 		root = dev->rcec;
> 	else
> 		root = dev;
> 
> -	if (root)
> -		aer = dev->aer_cap;
> +	/*
> +	 * If the platform retained control of AER, an RCiEP may not have
> +	 * an RCEC visible to us, so dev->rcec ("root") may be NULL.  In
> +	 * that case, firmware is responsible for these registers.
> +	 */
> +	aer = root ? root->aer_cap : 0;
> 
> -	if ((aer) && pcie_aer_is_native(dev)) {
> +	if ((host->native_aer || pcie_ports_native) && 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;
> @@ -1403,13 +1408,15 @@ static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
> 		if (pcie_has_flr(dev)) {
> 			rc = pcie_flr(dev);
> 			pci_info(dev, "has been reset (%d)\n", rc);
> +		} else {
> +			pci_info(dev, "not reset (no FLR support)\n");
> 		}
> 	} else {
> 		rc = pci_bus_error_reset(dev);
> 		pci_info(dev, "Root Port link has been reset (%d)\n", rc);
> 	}
> 
> -	if ((aer) && pcie_aer_is_native(dev)) {
> +	if ((host->native_aer || pcie_ports_native) && 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);
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index cbc5abfe767b..510f31f0ef6d 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -148,30 +148,23 @@ 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,
> - *           or a Port.
> - * @cb       callback to be called for each device found
> - * @userdata arbitrary pointer to be passed to callback.
> + * @bridge:	bridge which may be a Port, an RCEC, or an RCiEP
> + * @cb:		callback to be called for each device found
> + * @userdata:	arbitrary pointer to be passed to callback
>  *
>  * If the device provided is a bridge, walk the subordinate bus, including
>  * any bridged devices on buses under this bus.  Call the provided callback
>  * on each device found.
>  *
> - * If the device provided has no subordinate bus, call the callback on the
> - * device itself.
> + * If the device provided has no subordinate bus, e.g., an RCEC or RCiEP,
> + * call the callback on the device itself.
>  */
> static void pci_walk_bridge(struct pci_dev *bridge,
> 			    int (*cb)(struct pci_dev *, void *),
> 			    void *userdata)
> {
> -	/*
> -	 * In a non-native case where there is no OS-visible reporting
> -	 * device the bridge will be NULL, i.e., no RCEC, no Downstream Port.
> -	 */
> 	if (bridge->subordinate)
> 		pci_walk_bus(bridge->subordinate, cb, userdata);
> -	else if (bridge->rcec)
> -		cb(bridge->rcec, userdata);
> 	else
> 		cb(bridge, userdata);
> }
> @@ -183,11 +176,16 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> 	int type = pci_pcie_type(dev);
> 	struct pci_dev *bridge;
> 	pci_ers_result_t status = PCI_ERS_RESULT_CAN_RECOVER;
> +	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
> 
> 	/*
> -	 * Error recovery runs on all subordinates of the bridge.  If the
> -	 * bridge detected the error, it is cleared at the end.  For RCiEPs
> -	 * we should reset just the RCiEP itself.
> +	 * If the error was detected by a Root Port, Downstream Port, RCEC,
> +	 * or RCiEP, recovery runs on the device itself.  For Ports, that
> +	 * also includes any subordinate devices.
> +	 *
> +	 * If it was detected by another device (Endpoint, etc), recovery
> +	 * runs on the device and anything else under the same Port, i.e.,
> +	 * everything under "bridge".
> 	 */
> 	if (type == PCI_EXP_TYPE_ROOT_PORT ||
> 	    type == PCI_EXP_TYPE_DOWNSTREAM ||
> @@ -232,11 +230,15 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> 	pci_dbg(bridge, "broadcast resume message\n");
> 	pci_walk_bridge(bridge, report_resume, &status);
> 
> -	if (type == PCI_EXP_TYPE_ROOT_PORT ||
> -	    type == PCI_EXP_TYPE_DOWNSTREAM ||
> -	    type == PCI_EXP_TYPE_RC_EC) {
> -		if (pcie_aer_is_native(bridge))
> -			pcie_clear_device_status(bridge);
> +	/*
> +	 * If we have native control of AER, clear error status in the Root
> +	 * Port or Downstream Port that signaled the error.  If the
> +	 * platform retained control of AER, it is responsible for clearing
> +	 * this status.  In that case, the signaling device may not even be
> +	 * visible to the OS.
> +	 */
> +	if (host->native_aer || pcie_ports_native) {
> +		pcie_clear_device_status(bridge);
> 		pci_aer_clear_nonfatal_status(bridge);
> 	}
> 	pci_info(bridge, "device recovery successful\n");

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