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

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Date:   Mon, 27 Jul 2020 17:11:04 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Sean V Kelley <sean.v.kelley@...el.com>
CC:     <bhelgaas@...gle.com>, <rjw@...ysocki.net>, <ashok.raj@...nel.org>,
        <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 Mon, 27 Jul 2020 12:23:58 +0100
Jonathan Cameron <Jonathan.Cameron@...wei.com> 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
> 
> > ---
> >  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);
> 
> 
> >  			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);
This needs updating as well to match current approach in Bjorn's tree

(reworked version of my fix for this in th !is_native case)

> > +		pci_aer_clear_nonfatal_status(dev->rcec);  
> 
> These may be safe as in my both now have protections for !pcie_aer_is_native.
Except I'm wrong.  That function performs a local check based
on the pci_dev passed in, so blows up anyway.

So this whole block needs an if(dev->rcec), or potentially protect it with
a call to pci_aer_is_native(dev) on the basis we shouldn't be able to get
here unless we are not doing native aer or we have an rcec.

Jonathan

> 
> >  	}
> > +
> >  	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!
> 
> > +
> > +	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 */  
>