Re: [PATCHv2 pci-next 2/2] PCI/AER: Rate limit the reporting of the correctable errors

Grant Grundler
2023-05-18T05:58:38Z

[-- Attachment #1: Type: text/plain, Size: 3007 bytes --]

On Wed, May 17, 2023 at 9:03 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Fri, Apr 07, 2023 at 04:46:03PM -0700, Grant Grundler wrote:
> > On Fri, Apr 7, 2023 at 12:46 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > On Fri, Apr 07, 2023 at 11:53:27AM -0700, Grant Grundler wrote:
> > > > On Thu, Apr 6, 2023 at 12:50 PM Bjorn Helgaas <helgaas@kernel.org>
> > > wrote:
> > > > > On Fri, Mar 17, 2023 at 10:51:09AM -0700, Grant Grundler wrote:
> > > > > > From: Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
> > > > > >
> > > > > > There are many instances where correctable errors tend to inundate
> > > > > > the message buffer. We observe such instances during thunderbolt PCIe
> > > > > > tunneling.
> > > > ...
> > >
> > > > > > if (info->severity == AER_CORRECTABLE)
> > > > > > - pci_info(dev, " [%2d] %-22s%s\n", i, errmsg,
> > > > > > - info->first_error == i ? " (First)" :
> > > "");
> > > > > > + pci_info_ratelimited(dev, " [%2d]
> > > %-22s%s\n", i, errmsg,
> > > > > > + info->first_error == i ?
> > > " (First)" : "");
> > > > >
> > > > > I don't think this is going to reliably work the way we want. We have
> > > > > a bunch of pci_info_ratelimited() calls, and each caller has its own
> > > > > ratelimit_state data. Unless we call pci_info_ratelimited() exactly
> > > > > the same number of times for each error, the ratelimit counters will
> > > > > get out of sync and we'll end up printing fragments from error A mixed
> > > > > with fragments from error B.

Despite consolidating the error output, my impression is this is still
possible. :(

...
> > > Rate-limiting is per call location, so yes, if we only have one call
> > > location, that would solve it. It would also have the nice property
> > > that all the output would be atomic so it wouldn't get mixed with
> > > other stuff, and it might encourage us to be a little less wordy in
> > > the output.

Unfortunately, I think this needs further surgery.

> > +1 to all of those reasons. Especially reducing the number of lines output.
> >
> > I'm going to be out for the next week. If someone else (Rajat Kendalwal
> > maybe?) wants to rework this to use one call location it should be fairly
> > straight forward. If not, I'll tackle this when I'm back (in 2 weeks
> > essentially).
>
> Ping? Really hoping to merge this for v6.5.

I've appended what I have now... but there are still two issues:
1) we still end up with two "pci_info_ratelimited" call locations: one
in aer_print_err() and another in __aer_print_err().
2) I just noticed both functions output info->status and info->mask
(so this ends up getting printed twice in different formats).

and that's not really even looking carefully at the other call site:
cper_print_aer()

If this is "good enough" for now, I can repost as v3.

cheers,
grant

[-- Attachment #2: 0001-PCI-AER-correctable-error-message-as-KERN_INFO.patch --]
[-- Type: text/x-patch, Size: 2935 bytes --]

From 5ee8c86ce0496be66784eff94e0b165be33f83f4 Mon Sep 17 00:00:00 2001
From: Grant Grundler <grundler@chromium.org>
Date: Tue, 28 Feb 2023 22:04:53 -0800
Subject: [PATCH 1/2] PCI/AER: correctable error message as KERN_INFO

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@chromium.org>
---
drivers/pci/pcie/aer.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index f6c24ded134c..d7bfc6070ddb 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],
@@ -797,14 +797,22 @@ void cper_print_aer(struct pci_dev *dev, int aer_severity,
info.mask = mask;
info.first_error = PCI_ERR_CAP_FEP(aer->cap_control);

- pci_err(dev, "aer_status: 0x%08x, aer_mask: 0x%08x\n", status, mask);
+ if (aer_severity == AER_CORRECTABLE)
+ pci_info(dev, "aer_status: 0x%08x, aer_mask: 0x%08x\n", status, mask);
+ else
+ pci_err(dev, "aer_status: 0x%08x, aer_mask: 0x%08x\n", status, mask);
+
__aer_print_error(dev, &info);
- pci_err(dev, "aer_layer=%s, aer_agent=%s\n",
- aer_error_layer[layer], aer_agent_string[agent]);

- if (aer_severity != AER_CORRECTABLE)
+ if (aer_severity == AER_CORRECTABLE) {
+ pci_info(dev, "aer_layer=%s, aer_agent=%s\n",
+ aer_error_layer[layer], aer_agent_string[agent]);
+ } else {
+ pci_err(dev, "aer_layer=%s, aer_agent=%s\n",
+ aer_error_layer[layer], aer_agent_string[agent]);
pci_err(dev, "aer_uncor_severity: 0x%08x\n",
aer->uncor_severity);
+ }

if (tlp_header_valid)
__print_tlp_header(dev, &aer->header_log);
--
2.40.1.606.ga4b1b128d6-goog

[-- Attachment #3: 0002-PCI-AER-Rate-limit-the-reporting-of-the-correctable-.patch --]
[-- Type: text/x-patch, Size: 6811 bytes --]

From 70821bbf58a9ff1ea33dcdf8be17023f2437d4eb Mon Sep 17 00:00:00 2001
From: Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
Date: Tue, 3 Jan 2023 22:25:48 +0530
Subject: [PATCH 2/2] PCI/AER: Rate limit the reporting of the correctable
errors

There are many instances where correctable errors tend to inundate
the message buffer. We observe such instances during thunderbolt PCIe
tunneling.

It's true that they are mitigated by the hardware and are non-fatal
but we shouldn't be spamming the logs with such correctable errors as it
confuses other kernel developers less familiar with PCI errors, support
staff, and users who happen to look at the logs, hence rate limit them.

A typical example log inside an HP TBT4 dock:
[54912.661142] pcieport 0000:00:07.0: AER: Multiple Corrected error received: 0000:2b:00.0
[54912.661194] igc 0000:2b:00.0: PCIe Bus Error: severity=Corrected, type=Data Link Layer, (Transmitter ID)
[54912.661203] igc 0000:2b:00.0: device [8086:5502] error status/mask=00001100/00002000
[54912.661211] igc 0000:2b:00.0: [ 8] Rollover
[54912.661219] igc 0000:2b:00.0: [12] Timeout
[54982.838760] pcieport 0000:00:07.0: AER: Corrected error received: 0000:2b:00.0
[54982.838798] igc 0000:2b:00.0: PCIe Bus Error: severity=Corrected, type=Data Link Layer, (Transmitter ID)
[54982.838808] igc 0000:2b:00.0: device [8086:5502] error status/mask=00001000/00002000
[54982.838817] igc 0000:2b:00.0: [12] Timeout

This gets repeated continuously, thus inundating the buffer.

Signed-off-by: Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
Signed-off-by: Grant Grundler <grundler@chromium.org>
---
drivers/pci/pcie/aer.c | 80 +++++++++++++++++++++++++++---------------
1 file changed, 51 insertions(+), 29 deletions(-)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index d7bfc6070ddb..830f5a1261c9 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -686,26 +686,36 @@ static void __aer_print_error(struct pci_dev *dev,
struct aer_err_info *info)
{
const char **strings;
+ char aer_msg[512];
unsigned long status = info->status & ~info->mask;
- const char *level, *errmsg;
int i;

- if (info->severity == AER_CORRECTABLE) {
- strings = aer_correctable_error_string;
- level = KERN_INFO;
- } else {
- strings = aer_uncorrectable_error_string;
- level = KERN_ERR;
- }
+ memset(aer_msg, 0, sizeof(*aer_msg));
+ snprintf(aer_msg, sizeof(*aer_msg), "aer_status: 0x%08x, aer_mask: 0x%08x\n",
+ info->status, info->mask);
+
+ strings = (info->severity == AER_CORRECTABLE) ?
+ aer_correctable_error_string : aer_uncorrectable_error_string;

for_each_set_bit(i, &status, 32) {
- errmsg = strings[i];
+ const char *errmsg = strings[i];
+ char bitmsg[64];
+ memset(bitmsg, 0, sizeof(*bitmsg));
+
if (!errmsg)
errmsg = "Unknown Error Bit";

- pci_printk(level, dev, " [%2d] %-22s%s\n", i, errmsg,
- info->first_error == i ? " (First)" : "");
+ snprintf(bitmsg, sizeof(*bitmsg), " [%2d] %-22s%s\n", i, errmsg,
+ info->first_error == i ? " (First)" : "");
+
+ strlcat(aer_msg, bitmsg, sizeof(*aer_msg));
}
+
+ if (info->severity == AER_CORRECTABLE)
+ pci_info_ratelimited(dev, "%s", aer_msg);
+ else
+ pci_err(dev, "%s", aer_msg):
+
pci_dev_aer_stats_incr(dev, info);
}

@@ -713,7 +723,6 @@ void aer_print_error(struct pci_dev *dev, struct aer_err_info *info)
{
int layer, agent;
int id = ((dev->bus->number << 8) | dev->devfn);
- const char *level;

if (!info->status) {
pci_err(dev, "PCIe Bus Error: severity=%s, type=Inaccessible, (Unregistered Agent ID)\n",
@@ -724,14 +733,19 @@ 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_INFO : KERN_ERR;
-
- pci_printk(level, dev, "PCIe Bus Error: severity=%s, type=%s, (%s)\n",
- aer_error_severity_string[info->severity],
- aer_error_layer[layer], aer_agent_string[agent]);
-
- pci_printk(level, dev, " device [%04x:%04x] error status/mask=%08x/%08x\n",
- dev->vendor, dev->device, info->status, info->mask);
+ if (info->severity == AER_CORRECTABLE) {
+ pci_info_ratelimited(dev, "PCIe Bus Error: severity=%s, type=%s, (%s)\n"
+ " device [%04x:%04x] error status/mask=%08x/%08x\n",
+ aer_error_severity_string[info->severity],
+ aer_error_layer[layer], aer_agent_string[agent],
+ dev->vendor, dev->device, info->status, info->mask);
+ } else {
+ pci_err(dev, "PCIe Bus Error: severity=%s, type=%s, (%s)\n",
+ " device [%04x:%04x] error status/mask=%08x/%08x\n",
+ aer_error_severity_string[info->severity],
+ aer_error_layer[layer], aer_agent_string[agent],
+ dev->vendor, dev->device, info->status, info->mask);
+ }

__aer_print_error(dev, info);

@@ -751,11 +765,19 @@ static void aer_print_port_info(struct pci_dev *dev, struct aer_err_info *info)
u8 bus = info->id >> 8;
u8 devfn = info->id & 0xff;

- pci_info(dev, "%s%s error received: %04x:%02x:%02x.%d\n",
- info->multi_error_valid ? "Multiple " : "",
- aer_error_severity_string[info->severity],
- pci_domain_nr(dev->bus), bus, PCI_SLOT(devfn),
- PCI_FUNC(devfn));
+ if (info->severity == AER_CORRECTABLE)
+ pci_info_ratelimited(dev, "%s%s error received: %04x:%02x:%02x.%d\n",
+ info->multi_error_valid ? "Multiple " : "",
+ aer_error_severity_string[info->severity],
+ pci_domain_nr(dev->bus), bus, PCI_SLOT(devfn),
+ PCI_FUNC(devfn));
+ else
+ pci_info(dev, "%s%s error received: %04x:%02x:%02x.%d\n",
+ info->multi_error_valid ? "Multiple " : "",
+ aer_error_severity_string[info->severity],
+ pci_domain_nr(dev->bus), bus, PCI_SLOT(devfn),
+ PCI_FUNC(devfn));
+
}

#ifdef CONFIG_ACPI_APEI_PCIEAER
@@ -798,7 +820,7 @@ void cper_print_aer(struct pci_dev *dev, int aer_severity,
info.first_error = PCI_ERR_CAP_FEP(aer->cap_control);

if (aer_severity == AER_CORRECTABLE)
- pci_info(dev, "aer_status: 0x%08x, aer_mask: 0x%08x\n", status, mask);
+ pci_info_ratelimited(dev, "aer_status: 0x%08x, aer_mask: 0x%08x\n", status, mask);
else
pci_err(dev, "aer_status: 0x%08x, aer_mask: 0x%08x\n", status, mask);

@@ -808,9 +830,9 @@ void cper_print_aer(struct pci_dev *dev, int aer_severity,
pci_info(dev, "aer_layer=%s, aer_agent=%s\n",
aer_error_layer[layer], aer_agent_string[agent]);
} else {
- pci_err(dev, "aer_layer=%s, aer_agent=%s\n",
- aer_error_layer[layer], aer_agent_string[agent]);
- pci_err(dev, "aer_uncor_severity: 0x%08x\n",
+ pci_err(dev, "aer_layer=%s, aer_agent=%s,"
+ " aer_uncor_severity=0x%08x\n",
+ aer_error_layer[layer], aer_agent_string[agent],
aer->uncor_severity);
}

--
2.40.1.606.ga4b1b128d6-goog