linux-kernel - Re: [PATCH] PCI/AER: correctable error message as KERN

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Message-ID: <CANEJEGt6oNVvPpUgt=Zi8P_gUp09EctKt+uBiRfO0Cx5gsUvPA@mail.gmail.com>
Date:   Fri, 17 Mar 2023 10:57:24 -0700
From:   Grant Grundler <grundler@...omium.org>
To:     Grant Grundler <grundler@...omium.org>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        "Oliver O 'Halloran" <oohall@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rajat Khandelwal <rajat.khandelwal@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Rajat Jain <rajatja@...omium.org>
Subject: Re: [PATCH] PCI/AER: correctable error message as KERN_INFO

On Tue, Mar 14, 2023 at 5:24 PM Grant Grundler <grundler@...omium.org> wrote:
>
> On Tue, Mar 14, 2023 at 12:38 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
> >
> > On Tue, Feb 28, 2023 at 10:04:53PM -0800, Grant Grundler wrote:
> > > Since correctable errors have been corrected (and counted), the dmesg output
> > > should not be reported as a warning, but rather as "informational".
> > >
> > > Otherwise, using a certain well known vendor's PCIe parts in a USB4 docking
> > > station, the dmesg buffer can be spammed with correctable errors, 717 bytes
> > > per instance, potentially many MB per day.
> > >
> > > Given the "WARN" priority, these messages have already confused the typical
> > > user that stumbles across them, support staff (triaging feedback reports),
> > > and more than a few linux kernel devs. Changing to INFO will hide these
> > > messages from most audiences.
> > >
> > > Signed-off-by: Grant Grundler <grundler@...omium.org>
> > > ---
> > > This patch will likely conflict with:
> > >   https://lore.kernel.org/all/20230103165548.570377-1-rajat.khandelwal@linux.intel.com/
> > >
> > > which I'd also like to see upstream. Please let me know to resubmit
> > > mine if Rajat's patch lands first. Or feel free to fix up this one.
> >
> > Yes.  I think it makes sense to separate this into two patches:
> >
> >   1) Log correctable errors as KERN_INFO instead of KERN_WARNING, and
> >   2) Rate-limit correctable error logging.
>
> I'm going to look into your comment below. I'll port Rajat's patch on
> top of mine to follow the order you've listed above.
>
> > >  drivers/pci/pcie/aer.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > > index f6c24ded134c..e4cf3ec40d66 100644
> > > --- a/drivers/pci/pcie/aer.c
> > > +++ b/drivers/pci/pcie/aer.c
> > > @@ -692,7 +692,7 @@ static void __aer_print_error(struct pci_dev *dev,
> > >
> > >       if (info->severity == AER_CORRECTABLE) {
> > >               strings = aer_correctable_error_string;
> > > -             level = KERN_WARNING;
> > > +             level = KERN_INFO;
> > >       } else {
> > >               strings = aer_uncorrectable_error_string;
> > >               level = KERN_ERR;
> > > @@ -724,7 +724,7 @@ void aer_print_error(struct pci_dev *dev, struct aer_err_info *info)
> > >       layer = AER_GET_LAYER_ERROR(info->severity, info->status);
> > >       agent = AER_GET_AGENT(info->severity, info->status);
> > >
> > > -     level = (info->severity == AER_CORRECTABLE) ? KERN_WARNING : KERN_ERR;
> > > +     level = (info->severity == AER_CORRECTABLE) ? KERN_INFO : KERN_ERR;
> > >
> > >       pci_printk(level, dev, "PCIe Bus Error: severity=%s, type=%s, (%s)\n",
> > >                  aer_error_severity_string[info->severity],
> >
> > Shouldn't we do the same in the cper_print_aer() path?  That path
> > currently uses pci_err() and then calls __aer_print_error(), so the
> > initial message will always be KERN_ERR, and the decoding done by
> > __aer_print_error() will be KERN_INFO (for correctable) or KERN_ERR.
>
> I was completely unaware of this since it's not causing me any
> immediate problems. But I agree the message priority should be
> consistent for correctable errors.

I've just posted a V2 which I believe is against "pci-next":

grundler <1607>git remote -v show pci-next
* remote pci-next
  Fetch URL: git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
  Push  URL: git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
  HEAD branch: main
  Remote branches:
    aer                   tracked
    controller/dt         tracked
    controller/kirin      tracked
    controller/layerscape tracked
    controller/rcar       tracked
    for-linus             tracked
    main                  tracked
    next                  tracked
  Local branch configured for 'git pull':
    aer_correctable_info merges with remote next

Please let me know if this is the wrong git tree and branch to track.

> > Seems like a shame to do the same test in three places, but would
> > require a little more refactoring to avoid that.
>
> I don't mind doing the same test in multiple places. If refactoring
> this isn't straight forward, I'll leave the refactoring for someone
> more ambitious. :D

I've moved one of the pci_info lines from cper_print_aer()  to
__aer_print_info() since the status/mask are the same for both paths
that invoke __aer_print_info(). But that's as far as I understand what
each of the paths that calls __aer_print_info() do.  If this is not
OK, I can move it back.

cheers,
grant