linux-kernel - Re: [RFC PATCH 6/9] PCI: Add 'rcec' field to pci

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Date:   Mon, 27 Jul 2020 08:39:43 -0700
From:   "Sean V Kelley" <sean.v.kelley@...el.com>
To:     "Jonathan Cameron" <Jonathan.Cameron@...wei.com>
Cc:     bhelgaas@...gle.com, rjw@...ysocki.net,
        "Raj, Ashok" <ashok.raj@...el.com>, tony.luck@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Qiuxu Zhuo" <qiuxu.zhuo@...el.com>
Subject: Re: [RFC PATCH 6/9] PCI: Add 'rcec' field to pci_dev for associated
 RCiEPs

On 27 Jul 2020, at 4:23, Jonathan Cameron wrote:

> On Fri, 24 Jul 2020 10:22:20 -0700
> Sean V Kelley <sean.v.kelley@...el.com> 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.
>> So add the 'rcec' field to the pci_dev structure and provide a hook 
>> for the
>> Root Port Driver to associate RCiEPs with their respective parent 
>> RCEC.
>>
>> Co-developed-by: Sean V Kelley <sean.v.kelley@...el.com>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
>
> I haven't tested yet, but I think there is one path in here that 
> breaks
> my case (no OS visible rcec / all done in firmware GHESv2 / APEI)
>
> Jonathan

Okay, keep me up to date and if there is a way I can reproduce or better 
test for your use case let me know and I will do so.

>
>> ---
>>  drivers/pci/pcie/aer.c         |  9 +++++----
>>  drivers/pci/pcie/err.c         |  9 +++++++++
>>  drivers/pci/pcie/portdrv_pci.c | 15 +++++++++++++++
>>  include/linux/pci.h            |  3 +++
>>  4 files changed, 32 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index 3acf56683915..f1bf06be449e 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -1335,17 +1335,18 @@ 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 9b3ec94bdf1d..0aae7643132e 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -203,6 +203,11 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev 
>> *dev,
>>  		pci_walk_dev_affected(dev, report_frozen_detected, &status);
>>  		if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
>>  			status = flr_on_rciep(dev);
>> +			/*
>> +			 * The callback only clears the Root Error Status
>> +			 * of the RCEC (see aer.c).
>> +			 */
>> +			reset_link(dev->rcec);
>
> This looks dangerous for my case where APEI / GHESv2 is used.  In that 
> case
> we don't expose an RCEC at all.   I don't think the reset_link 
> callback
> is safe to a null pointer here.  Fix may be as simple as
> if (dev->rcec)
> 	reset_link(dev->rcec);

Good catch.  Will look to NULL case as well as walk through code where 
dev->rcec is further referenced (below and elsewhere) to ensure nothing 
falls through. Glad you are pointing these out.

>
>
>>  			if (status != PCI_ERS_RESULT_RECOVERED) {
>>  				pci_warn(dev, "function level reset failed\n");
>>  				goto failed;
>> @@ -246,7 +251,11 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev 
>> *dev,
>>  	     pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)) {
>>  		pci_aer_clear_device_status(dev);
>>  		pci_aer_clear_nonfatal_status(dev);
>> +	} else if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
>> +		pci_aer_clear_device_status(dev->rcec);
>> +		pci_aer_clear_nonfatal_status(dev->rcec);
>
> These may be safe as in my both now have protections for 
> !pcie_aer_is_native.
>
I’ll have a look again for the NULL case

>>  	}
>> +
>>  	pci_info(dev, "device recovery successful\n");
>>  	return status;
>>
>> diff --git a/drivers/pci/pcie/portdrv_pci.c 
>> b/drivers/pci/pcie/portdrv_pci.c
>> index d5b109499b10..f9409a0110c2 100644
>> --- a/drivers/pci/pcie/portdrv_pci.c
>> +++ b/drivers/pci/pcie/portdrv_pci.c
>> @@ -90,6 +90,18 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops 
>> = {
>>  #define PCIE_PORTDRV_PM_OPS	NULL
>>  #endif /* !PM */
>>
>> +static int pcie_hook_rcec(struct pci_dev *pdev, void *data)
>> +{
>> +	struct pci_dev *rcec = (struct pci_dev *)data;
>> +
>> +	pdev->rcec = rcec;
>> +	pci_info(rcec, "RCiEP(under an RCEC) %04x:%02x:%02x.%d\n",
>> +		 pci_domain_nr(pdev->bus), pdev->bus->number,
>> +		 PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn));
>
> We may want to make this debug info at somepoint if we have a way
> of discovering it from userspace.   The PCI boot up is extremely
> verbose already!

I’ve submitted patches to pciutils, which expose this very detail:

https://lore.kernel.org/linux-pci/20200624223940.240463-1-sean.v.kelley@linux.intel.com/

Flexible either way, could remove or make it debug info.

Thanks,

Sean

>
>> +
>> +	return 0;
>> +}
>> +
>>  /*
>>   * pcie_portdrv_probe - Probe PCI-Express port devices
>>   * @dev: PCI-Express port device being probed
>> @@ -110,6 +122,9 @@ static int pcie_portdrv_probe(struct pci_dev 
>> *dev,
>>  	     (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC)))
>>  		return -ENODEV;
>>
>> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
>> +		pcie_walk_rcec(dev, pcie_hook_rcec, dev);
>> +
>>  	status = pcie_port_device_register(dev);
>>  	if (status)
>>  		return status;
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 34c1c4f45288..e920f29df40b 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -326,6 +326,9 @@ struct pci_dev {
>>  #ifdef CONFIG_PCIEAER
>>  	u16		aer_cap;	/* AER capability offset */
>>  	struct aer_stats *aer_stats;	/* AER stats for this device */
>> +#endif
>> +#ifdef CONFIG_PCIEPORTBUS
>> +	struct pci_dev	*rcec;		/* Associated RCEC device */
>>  #endif
>>  	u8		pcie_cap;	/* PCIe capability offset */
>>  	u8		msi_cap;	/* MSI capability offset */