Re: [PATCH v3 7/8] PCI/AER: Add sysfs attributes for log ratelimits

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Wed, 19 Mar 2025, Jon Pan-Doh wrote:

> Allow userspace to read/write log ratelimits per device (including
> enable/disable). Create aer/ sysfs directory to store them and any
> future aer configs.
> 
> Tested using aer-inject[1]. Configured correctable log ratelimit to 5.
> Sent 6 AER errors. Observed 5 errors logged while AER stats
> (cat /sys/bus/pci/devices/<dev>/aer_dev_correctable) shows 6.
> 
> Disabled ratelimiting and sent 6 more AER errors. Observed all 6 errors
> logged and accounted in AER stats (12 total errors).
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/gong.chen/aer-inject.git
> 
> Signed-off-by: Karolina Stolarek <karolina.stolarek@oracle.com>
> Signed-off-by: Jon Pan-Doh <pandoh@google.com>
> ---
>  .../testing/sysfs-bus-pci-devices-aer_stats   | 34 +++++++
>  Documentation/PCI/pcieaer-howto.rst           |  3 +
>  drivers/pci/pci-sysfs.c                       |  1 +
>  drivers/pci/pci.h                             |  1 +
>  drivers/pci/pcie/aer.c                        | 93 +++++++++++++++++++
>  5 files changed, 132 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
> index d1f67bb81d5d..4561653fdbde 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
> +++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
> @@ -117,3 +117,37 @@ Date:		July 2018
>  KernelVersion:	4.19.0
>  Contact:	linux-pci@vger.kernel.org, rajatja@google.com
>  Description:	Total number of ERR_NONFATAL messages reported to rootport.
> +
> +PCIe AER ratelimits
> +-------------------
> +
> +These attributes show up under all the devices that are AER capable.
> +They represent configurable ratelimits of logs per error type.
> +
> +See Documentation/PCI/pcieaer-howto.rst for more info on ratelimits.
> +
> +What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_log_enable
> +Date:		March 2025
> +KernelVersion:	6.15.0
> +Contact:	linux-pci@vger.kernel.org, pandoh@google.com
> +Description:	Writing 1/0 enables/disables AER log ratelimiting. Reading
> +		gets whether or not AER is currently enabled. Enabled by
> +		default.
> +
> +What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_in_5secs_cor_log
> +Date:		March 2025
> +KernelVersion:	6.15.0
> +Contact:	linux-pci@vger.kernel.org, pandoh@google.com
> +Description:	Ratelimit burst for correctable error logs. Writing a value
> +		changes the number of errors (burst) allowed per interval
> +		(5 second window) before ratelimiting. Reading gets the
> +		current ratelimit burst.
> +
> +What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_in_5secs_uncor_log
> +Date:		March 2025
> +KernelVersion:	6.15.0
> +Contact:	linux-pci@vger.kernel.org, pandoh@google.com
> +Description:	Ratelimit burst for uncorrectable error logs. Writing a
> +		value changes the number of errors (burst) allowed per
> +		interval (5 second window) before ratelimiting. Reading
> +		gets the current ratelimit burst.
> diff --git a/Documentation/PCI/pcieaer-howto.rst b/Documentation/PCI/pcieaer-howto.rst
> index 896d2a232a90..b45a2e18d1cf 100644
> --- a/Documentation/PCI/pcieaer-howto.rst
> +++ b/Documentation/PCI/pcieaer-howto.rst
> @@ -96,6 +96,9 @@ type (correctable vs. uncorrectable).
>  AER uses the default ratelimit of DEFAULT_RATELIMIT_BURST (10 events) over
>  DEFAULT_RATELIMIT_INTERVAL (5 seconds).
>  
> +Ratelimits are exposed in the form of sysfs attributes and configurable.
> +See Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats.

Why does the next patch immediately modify this? A patch series should try 
to avoid back and forth changes like that.

-- 
 i.

>  AER Statistics / Counters
>  -------------------------
>  
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index b46ce1a2c554..16de3093294e 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1801,6 +1801,7 @@ const struct attribute_group *pci_dev_attr_groups[] = {
>  	&pcie_dev_attr_group,
>  #ifdef CONFIG_PCIEAER
>  	&aer_stats_attr_group,
> +	&aer_attr_group,
>  #endif
>  #ifdef CONFIG_PCIEASPM
>  	&aspm_ctrl_attr_group,
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 9d63d32f041c..34633fe12201 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -889,6 +889,7 @@ void pci_no_aer(void);
>  void pci_aer_init(struct pci_dev *dev);
>  void pci_aer_exit(struct pci_dev *dev);
>  extern const struct attribute_group aer_stats_attr_group;
> +extern const struct attribute_group aer_attr_group;
>  void pci_aer_clear_fatal_status(struct pci_dev *dev);
>  int pci_aer_clear_status(struct pci_dev *dev);
>  int pci_aer_raw_clear_status(struct pci_dev *dev);
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 0bd20c4993d4..13227a94c9f9 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -631,6 +631,99 @@ const struct attribute_group aer_stats_attr_group = {
>  	.is_visible = aer_stats_attrs_are_visible,
>  };
>  
> +/*
> + * Ratelimit enable toggle uses interval value of
> + * 0: disabled
> + * DEFAULT_RATELIMIT_INTERVAL: enabled
> + */
> +static ssize_t ratelimit_log_enable_show(struct device *dev,
> +					 struct device_attribute *attr,
> +					 char *buf)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	bool enable = pdev->aer_report->cor_log_ratelimit.interval != 0;
> +
> +	return sysfs_emit(buf, "%d\n", enable);
> +}
> +
> +static ssize_t ratelimit_log_enable_store(struct device *dev,
> +					  struct device_attribute *attr,
> +					  const char *buf, size_t count)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	bool enable;
> +	int interval;
> +
> +	if (kstrtobool(buf, &enable) < 0)
> +		return -EINVAL;
> +
> +	if (enable)
> +		interval = DEFAULT_RATELIMIT_INTERVAL;
> +	else
> +		interval = 0;
> +
> +	pdev->aer_report->cor_log_ratelimit.interval = interval;
> +	pdev->aer_report->uncor_log_ratelimit.interval = interval;
> +	return count;
> +}
> +static DEVICE_ATTR_RW(ratelimit_log_enable);
> +
> +/*
> + * Ratelimits are doubled as a given error produces 2 logs (root port
> + * and endpoint) that should be under same ratelimit.
> + */
> +#define aer_ratelimit_burst_attr(name, ratelimit)			\
> +	static ssize_t							\
> +	name##_show(struct device *dev, struct device_attribute *attr,	\
> +		    char *buf)						\
> +{									\
> +	struct pci_dev *pdev = to_pci_dev(dev);				\
> +	return sysfs_emit(buf, "%d\n",					\
> +			  pdev->aer_report->ratelimit.burst / 2);	\
> +}									\
> +									\
> +	static ssize_t							\
> +	name##_store(struct device *dev, struct device_attribute *attr,	\
> +		     const char *buf, size_t count)			\
> +{									\
> +	struct pci_dev *pdev = to_pci_dev(dev);				\
> +	int burst;							\
> +									\
> +	if (kstrtoint(buf, 0, &burst) < 0)				\
> +		return -EINVAL;						\
> +									\
> +	pdev->aer_report->ratelimit.burst = burst * 2;			\
> +	return count;							\
> +}									\
> +static DEVICE_ATTR_RW(name)
> +
> +aer_ratelimit_burst_attr(ratelimit_in_5secs_cor_log, cor_log_ratelimit);
> +aer_ratelimit_burst_attr(ratelimit_in_5secs_uncor_log, uncor_log_ratelimit);
> +
> +static struct attribute *aer_attrs[] = {
> +	&dev_attr_ratelimit_log_enable.attr,
> +	&dev_attr_ratelimit_in_5secs_cor_log.attr,
> +	&dev_attr_ratelimit_in_5secs_uncor_log.attr,
> +	NULL
> +};
> +
> +static umode_t aer_attrs_are_visible(struct kobject *kobj,
> +				     struct attribute *a, int n)
> +{
> +	struct device *dev = kobj_to_dev(kobj);
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +
> +	if (!pdev->aer_report)
> +		return 0;
> +	return a->mode;
> +}
> +
> +const struct attribute_group aer_attr_group = {
> +	.name = "aer",
> +	.attrs = aer_attrs,
> +	.is_visible = aer_attrs_are_visible,
> +};
> +
>  void pci_dev_aer_stats_incr(struct pci_dev *pdev, struct aer_err_info *info)
>  {
>  	unsigned long status = info->status & ~info->mask;
>