On Thu, Jun 21, 2018 at 11:48 AM, Bjorn Helgaas [off-list ref] wrote:

[+cc Tyler for AER dmesg decoding]

I really like this idea a lot; thanks for putting it together!

On Wed, Jun 20, 2018 at 04:41:45PM -0700, Rajat Jain wrote:

quoted

Add sysfs attributes to provide breakdown of the AERs seen,
into different type of correctable or uncorrectable errors:

dev_breakdown_correctable
dev_breakdown_uncorrectable

- Can you include a more complete sysfs path here in the commit log,
  as well as a snippet of the contents?  From the doc patch, I think
  it is currently:

    /sys/bus/pci/devices/<dev>/aer_stats/dev_breakdown_correctable
    /sys/bus/pci/devices/<dev>/aer_stats/dev_breakdown_uncorrectable

- I'm not sure it's worth making a new subdirectory.  What if you
  simply added these?

Its your call. We're going to be creating 6 files for aer_stats (I'll
be following your suggestion below), and I think it may clutter the
directory. In my next patch, I'm going to remove the sub directory,
but we can add that later if you feel so.

    /sys/bus/pci/devices/<dev>/aer_correctable
    /sys/bus/pci/devices/<dev>/aer_uncorrectable

  or perhaps, since you split the "total" files into
  cor/nonfatal/fatal, these could match?

    /sys/bus/pci/devices/<dev>/aer_correctable
    /sys/bus/pci/devices/<dev>/aer_nonfatal
    /sys/bus/pci/devices/<dev>/aer_fatal

This sounds like a better idea.

  I think the nonfatal/fatal distinction might be worth exposing
  because some of those are configurable and the kernel handling is
  significantly different.  So I think it would make this more
  approachable if the "remove/re-enumerate" situations that will be
  obvious in dmesg logs were clearly connected with "aer_fatal"
  statistics, as opposed to being connected to some subset of what's
  in "aer_uncorrectable".

Agree, however note that theoretically, the classification of
uncorrectable errors into fatal or non fatal can be programmed /
changed (by who?), so it is possible that some of the same types of
errors may show up such that some instances in counted in fatal and
some in non-fatal (depending on whether those bits were set while
handling ERR_FATAL or ERR_NONFATAL respectively). Not that I think
there is something wrong with this, just thought I will mention.

- Possibly the totals that you currently have in dev_total_cor_errs
  could even be added to the bottom of these?  Not sure what direction
  would be best, and as you say, there's the potential for confusion
  because the individual items won't add up to the totals.  If they
  were in the same file, maybe that could be addressed in the label.

Agree, this also sounds good.

- Can you include the related doc update in the same patch?  That way
  the doc update is more likely to be backported along with the patch.

Will do.

- I was going to ask whether these should all be in a single file or
  whether they should be split up so there's a separate file for each
  type or error, each containing a single number.  But
  Documentation/filesystems/sysfs.txt says either is OK and
  /sys/devices/system/node/node0/vmstat is an example of a similar
  situation in an existing file, so I think what you did is perfect.

Thank you, I initially thought of having a different file for each
error, but then it looked like we're be having much more files - at
least large enough for the number of files to overwhelm the user
space.


Thanks,

Rajat

quoted

Signed-off-by: Rajat Jain <redacted>
---
v5: Fix the signature
v4: use "%llu" in place of "%llx"
v3: Merge everything in aer.c

 drivers/pci/pcie/aer.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index ce0d675d7bd3..c989bb5bb6f1 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c

@@ -587,10 +587,38 @@ aer_stats_aggregate_attr(dev_total_cor_errs);
 aer_stats_aggregate_attr(dev_total_fatal_errs);
 aer_stats_aggregate_attr(dev_total_nonfatal_errs);

+#define aer_stats_breakdown_attr(field, stats_array, strings_array)  \
+     static ssize_t                                                  \
+     field##_show(struct device *dev, struct device_attribute *attr, \
+                  char *buf)                                         \
+{                                                                    \
+     unsigned int i;                                                 \
+     char *str = buf;                                                \
+     struct pci_dev *pdev = to_pci_dev(dev);                         \
+     u64 *stats = pdev->aer_stats->stats_array;                      \

Nit: add a blank line here.

Will do.

quoted

+     for (i = 0; i < ARRAY_SIZE(strings_array); i++) {               \
+             if (strings_array[i])                                   \
+                     str += sprintf(str, "%s = 0x%llu\n",            \
+                                    strings_array[i], stats[i]);     \
+             else if (stats[i])                                      \
+                     str += sprintf(str, #stats_array "bit[%d] = 0x%llu\n",\
+                                    i, stats[i]);                    \

- I like the way this uses the same text as used in dmesg
  (aer_correctable_error_string[] and
  aer_uncorrectable_error_string[]).

- I think this incorrectly prints a "0x" prefix for a decimal number
  (probably an artifact of your v4 change).

Will do.

- Tyler posted a patch [1] to update those dmesg strings so they match
  the way lspci decodes them.  I really liked that update, but we
  never quite finished it.  If we're going to do that, it would be
  nice to do it first, so we don't publish new sysfs files, then
  immediately change the labels used in them.

Sure, I guess you can push them in the right order.

- IIRC, Tyler's patch had the nice property of changing the strings so
  each error name had no spaces, which would make it a little easier
  to parse this sysfs file: each line would be a single identifier
  followed by a single number (I would probably remove the "=" from
  the middle).

Will do.

[1] https://lkml.kernel.org/r/1518034285-3543-1-git-send-email-tbaicar@codeaurora.org

quoted

+     }                                                               \
+     return str-buf;                                                 \
+}                                                                    \
+static DEVICE_ATTR_RO(field)
+
+aer_stats_breakdown_attr(dev_breakdown_correctable, dev_cor_errs,
+                      aer_correctable_error_string);
+aer_stats_breakdown_attr(dev_breakdown_uncorrectable, dev_uncor_errs,
+                      aer_uncorrectable_error_string);
+
 static struct attribute *aer_stats_attrs[] __ro_after_init = {
      &dev_attr_dev_total_cor_errs.attr,
      &dev_attr_dev_total_fatal_errs.attr,
      &dev_attr_dev_total_nonfatal_errs.attr,
+     &dev_attr_dev_breakdown_correctable.attr,
+     &dev_attr_dev_breakdown_uncorrectable.attr,
      NULL
 };

--
2.18.0.rc1.244.gcf134e6275-goog

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