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

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Message-ID: <57dc908d-c158-9019-b86e-3c051b951d17@linux.intel.com>
Date: Tue, 20 May 2025 17:20:36 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Bjorn Helgaas <helgaas@...nel.org>
cc: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>, 
    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>, 
    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>, LKML <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 Tue, 20 May 2025, Bjorn Helgaas wrote:

> 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.

Instead of macros, it might be worth adding a printf specifier for this. 
Together with some flags, it should be possible to cover also the 
variations that print less than the full BDF format.

> > > +			 (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));
> 

-- 
 i.