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

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Date:   Tue, 14 Mar 2023 17:24:49 -0700
From:   Grant Grundler <grundler@...omium.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Grant Grundler <grundler@...omium.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 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.

> 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

cheers,
grant

>
> Bjorn