linux-kernel - Re: [PATCH v6 02/16] PCI/DPC: Log Error Source ID only when valid

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Message-ID: <20250520140025.GA1291490@bhelgaas>
Date: Tue, 20 May 2025 09:00:25 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: linux-pci@...r.kernel.org, Jon Pan-Doh <pandoh@...gle.com>,
	Karolina Stolarek <karolina.stolarek@...cle.com>,
	Martin Petersen <martin.petersen@...cle.com>,
	Ben Fuller <ben.fuller@...cle.com>,
	Drew Walton <drewwalton@...rosoft.com>,
	Anil Agrawal <anilagrawal@...a.com>,
	Tony Luck <tony.luck@...el.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Lukas Wunner <lukas@...ner.de>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Sargun Dhillon <sargun@...a.com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
	Oliver O'Halloran <oohall@...il.com>,
	Kai-Heng Feng <kaihengf@...dia.com>,
	Keith Busch <kbusch@...nel.org>, Robert Richter <rrichter@....com>,
	Terry Bowman <terry.bowman@....com>,
	Shiju Jose <shiju.jose@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v6 02/16] PCI/DPC: Log Error Source ID only when valid

On Mon, May 19, 2025 at 04:15:56PM -0700, Sathyanarayanan Kuppuswamy wrote:
> On 5/19/25 2:35 PM, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@...gle.com>
> > 
> > DPC Error Source ID is only valid when the DPC Trigger Reason indicates
> > that DPC was triggered due to reception of an ERR_NONFATAL or ERR_FATAL
> > Message (PCIe r6.0, sec 7.9.14.5).
> > 
> > When DPC was triggered by ERR_NONFATAL (PCI_EXP_DPC_STATUS_TRIGGER_RSN_NFE)
> > or ERR_FATAL (PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE) from a downstream device,
> > log the Error Source ID (decoded into domain/bus/device/function).  Don't
> > print the source otherwise, since it's not valid.
> > 
> > For DPC trigger due to reception of ERR_NONFATAL or ERR_FATAL, the dmesg
> > logging changes:
> > 
> >    - pci 0000:00:01.0: DPC: containment event, status:0x000d source:0x0200
> >    - pci 0000:00:01.0: DPC: ERR_FATAL detected
> >    + pci 0000:00:01.0: DPC: containment event, status:0x000d, ERR_FATAL received from 0000:02:00.0
> > 
> > and when DPC triggered for other reasons, where DPC Error Source ID is
> > undefined, e.g., unmasked uncorrectable error:
> > 
> >    - pci 0000:00:01.0: DPC: containment event, status:0x0009 source:0x0200
> >    - pci 0000:00:01.0: DPC: unmasked uncorrectable error detected
> >    + pci 0000:00:01.0: DPC: containment event, status:0x0009: unmasked uncorrectable error detected
> > 
> > Previously the "containment event" message was at KERN_INFO and the
> > "%s detected" message was at KERN_WARNING.  Now the single message is at
> > KERN_WARNING.
> 
> Since we are handling Uncorrectable errors, why not use pci_err?

Sounds reasonable to me.  I would do it in a separate patch because
the point of this one is to avoid logging junk when Error Source ID is
not valid.

> > +		pci_warn(pdev, "containment event, status:%#06x, %s received from %04x:%02x:%02x.%d\n",
> > +			 status,
> 
> I see the BDF extraction and format code in many places in the PCI
> drivers. May be a common macro will make it more readable.

Good idea.  Not sure how to implement it, so I put that on my TODO
list for now.

> > +			 (reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE) ?
> > +				"ERR_FATAL" : "ERR_NONFATAL",
> > +			 pci_domain_nr(pdev->bus), PCI_BUS_NUM(source),
> > +			 PCI_SLOT(source), PCI_FUNC(source));