Subject: Re: [PATCH v3 6/6] PCI/AER: Unmask RCEC internal errors to enable RCH downstream port error handling

From: Jonathan Cameron <[email-masked]>
Date: Thu, 13 Apr 2023 18:01:22 +0100

On Wed, 12 Apr 2023 16:29:01 -0500
Bjorn Helgaas <[email-masked]> wrote:

> On Tue, Apr 11, 2023 at 01:03:02PM -0500, Terry Bowman wrote:
> > From: Robert Richter <[email-masked]>
> > 
> > RCEC AER corrected and uncorrectable internal errors (CIE/UIE) are
> > disabled by default.  
> 
> "Disabled by default" just means "the power-up state of CIE/UIC is
> that they are masked", right?  It doesn't mean that Linux normally
> masks them.
> 
> > [1][2] Enable them to receive CXL downstream port
> > errors of a Restricted CXL Host (RCH).
> > 
> > [1] CXL 3.0 Spec, 12.2.1.1 - RCH Downstream Port Detected Errors
> > [2] PCIe Base Spec 6.0, 7.8.4.3 Uncorrectable Error Mask Register,
> >     7.8.4.6 Correctable Error Mask Register
> > 
> > Co-developed-by: Terry Bowman <[email-masked]>
> > Signed-off-by: Robert Richter <[email-masked]>
> > Signed-off-by: Terry Bowman <[email-masked]>
> > Cc: "Oliver O'Halloran" <[email-masked]>
> > Cc: Bjorn Helgaas <[email-masked]>
> > Cc: Mahesh J Salgaonkar <[email-masked]>
> > Cc: [email-masked]
> > Cc: [email-masked]
> > ---
> >  drivers/pci/pcie/aer.c | 73 ++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 73 insertions(+)
> > 
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index 171a08fd8ebd..3973c731e11d 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -1000,7 +1000,79 @@ static void cxl_handle_error(struct pci_dev *dev, struct aer_err_info *info)
> >  		pcie_walk_rcec(dev, cxl_handle_error_iter, info);
> >  }
> >  
> > +static bool cxl_error_is_native(struct pci_dev *dev)
> > +{
> > +	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
> > +
> > +	if (pcie_ports_native)
> > +		return true;
> > +
> > +	return host->native_aer && host->native_cxl_error;
> > +}
> > +
> > +static int handles_cxl_error_iter(struct pci_dev *dev, void *data)
> > +{
> > +	int *handles_cxl = data;
> > +
> > +	*handles_cxl = is_cxl_mem_dev(dev) && cxl_error_is_native(dev);
> > +
> > +	return *handles_cxl;
> > +}
> > +
> > +static bool handles_cxl_errors(struct pci_dev *rcec)
> > +{
> > +	int handles_cxl = 0;
> > +
> > +	if (!rcec->aer_cap)
> > +		return false;
> > +
> > +	if (pci_pcie_type(rcec) == PCI_EXP_TYPE_RC_EC)
> > +		pcie_walk_rcec(rcec, handles_cxl_error_iter, &handles_cxl);
> > +
> > +	return !!handles_cxl;
> > +}
> > +
> > +static int __cxl_unmask_internal_errors(struct pci_dev *rcec)
> > +{
> > +	int aer, rc;
> > +	u32 mask;
> > +
> > +	/*
> > +	 * Internal errors are masked by default, unmask RCEC's here
> > +	 * PCI6.0 7.8.4.3 Uncorrectable Error Mask Register (Offset 08h)
> > +	 * PCI6.0 7.8.4.6 Correctable Error Mask Register (Offset 14h)
> > +	 */  
> 
> Unmasking internal errors doesn't have anything specific to do with
> CXL, so I don't think it should have "cxl" in the function name.
> Maybe something like "pci_aer_unmask_internal_errors()".

This reminds me.  Not sure we resolved earlier discussion on changing
the system wide policy to turn these on 
https://lore.kernel.org/linux-cxl/20221229172731.GA611562@bhelgaas/
which needs pretty much the same thing.

Ira, I think you were picking this one up?
https://lore.kernel.org/linux-cxl/[email-masked]/

Thanks,

Jonathan

> 
> This also has nothing special to do with RCECs, so I think we should
> refer to the device as "dev" as is typical in this file.
> 
> I think this needs to check pcie_aer_is_native() as is done by
> pci_aer_clear_nonfatal_status() and other functions that write the AER
> Capability.
> 
> With the exception of this function, this patch looks like all CXL
> code that maybe could be with other CXL code.  Would require making
> pcie_walk_rcec() available outside drivers/pci, I guess.
> 
> > +	aer = rcec->aer_cap;
> > +	rc = pci_read_config_dword(rcec, aer + PCI_ERR_UNCOR_MASK, &mask);
> > +	if (rc)
> > +		return rc;
> > +	mask &= ~PCI_ERR_UNC_INTN;
> > +	rc = pci_write_config_dword(rcec, aer + PCI_ERR_UNCOR_MASK, mask);
> > +	if (rc)
> > +		return rc;
> > +
> > +	rc = pci_read_config_dword(rcec, aer + PCI_ERR_COR_MASK, &mask);
> > +	if (rc)
> > +		return rc;
> > +	mask &= ~PCI_ERR_COR_INTERNAL;
> > +	rc = pci_write_config_dword(rcec, aer + PCI_ERR_COR_MASK, mask);
> > +
> > +	return rc;
> > +}
> > +
> > +static void cxl_unmask_internal_errors(struct pci_dev *rcec)
> > +{
> > +	if (!handles_cxl_errors(rcec))
> > +		return;
> > +
> > +	if (__cxl_unmask_internal_errors(rcec))
> > +		dev_err(&rcec->dev, "cxl: Failed to unmask internal errors");
> > +	else
> > +		dev_dbg(&rcec->dev, "cxl: Internal errors unmasked");
> > +}
> > +
> >  #else
> > +static inline void cxl_unmask_internal_errors(struct pci_dev *dev) { }
> >  static inline void cxl_handle_error(struct pci_dev *dev,
> >  				    struct aer_err_info *info) { }
> >  #endif
> > @@ -1397,6 +1469,7 @@ static int aer_probe(struct pcie_device *dev)
> >  		return status;
> >  	}
> >  
> > +	cxl_unmask_internal_errors(port);
> >  	aer_enable_rootport(rpc);
> >  	pci_info(port, "enabled with IRQ %d\n", dev->irq);
> >  	return 0;
> > -- 
> > 2.34.1
> >