Date:   Tue, 8 Mar 2022 10:23:26 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Yicong Yang <yangyicong@...ilicon.com>
CC:     <gregkh@...uxfoundation.org>, <helgaas@...nel.org>,
        <alexander.shishkin@...ux.intel.com>, <lorenzo.pieralisi@....com>,
        <will@...nel.org>, <mark.rutland@....com>,
        <mathieu.poirier@...aro.org>, <suzuki.poulose@....com>,
        <mike.leach@...aro.org>, <leo.yan@...aro.org>,
        <daniel.thompson@...aro.org>, <joro@...tes.org>,
        <john.garry@...wei.com>, <shameerali.kolothum.thodi@...wei.com>,
        <robin.murphy@....com>, <peterz@...radead.org>, <mingo@...hat.com>,
        <acme@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <coresight@...ts.linaro.org>, <linux-pci@...r.kernel.org>,
        <linux-perf-users@...r.kernel.org>,
        <iommu@...ts.linux-foundation.org>, <prime.zeng@...wei.com>,
        <liuqi115@...wei.com>, <zhangshaokun@...ilicon.com>,
        <linuxarm@...wei.com>, <song.bao.hua@...ilicon.com>
Subject: Re: [PATCH v5 4/8] hisi_ptt: Add support for dynamically updating
 the filter list

On Tue, 8 Mar 2022 16:49:26 +0800
Yicong Yang <yangyicong@...ilicon.com> wrote:

> The PCIe devices supported by the PTT trace can be removed/rescanned by
> hotplug or through sysfs.  Add support for dynamically updating the
> available filter list by registering a PCI bus notifier block. Then user
> can always get latest information about available tracing filters and
> driver can block the invalid filters of which related devices no longer
> exist in the system.
> 
> Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>
You've made the change I requested in v4 so

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  drivers/hwtracing/ptt/hisi_ptt.c | 157 ++++++++++++++++++++++++++++---
>  drivers/hwtracing/ptt/hisi_ptt.h |  34 +++++++
>  2 files changed, 176 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
> index f06fbbb8a12a..953d36dfcc89 100644
> --- a/drivers/hwtracing/ptt/hisi_ptt.c
> +++ b/drivers/hwtracing/ptt/hisi_ptt.c
> @@ -270,25 +270,118 @@ static int hisi_ptt_register_irq(struct hisi_ptt *hisi_ptt)
>  	return 0;
>  }
>  
> -static int hisi_ptt_init_filters(struct pci_dev *pdev, void *data)
> +static void hisi_ptt_update_filters(struct work_struct *work)
>  {
> +	struct delayed_work *delayed_work = to_delayed_work(work);
> +	struct hisi_ptt_filter_update_info info;
>  	struct hisi_ptt_filter_desc *filter;
> -	struct hisi_ptt *hisi_ptt = data;
>  	struct list_head *target_list;
> +	struct hisi_ptt *hisi_ptt;
>  
> -	target_list = pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT ?
> -		      &hisi_ptt->port_filters : &hisi_ptt->req_filters;
> +	hisi_ptt = container_of(delayed_work, struct hisi_ptt, work);
>  
> -	filter = kzalloc(sizeof(*filter), GFP_KERNEL);
> -	if (!filter)
> -		return -ENOMEM;
> +	if (!mutex_trylock(&hisi_ptt->mutex)) {
> +		schedule_delayed_work(&hisi_ptt->work, HISI_PTT_WORK_DELAY_MS);
> +		return;
> +	}
> +
> +	while (kfifo_get(&hisi_ptt->filter_update_kfifo, &info)) {
> +		bool is_port = pci_pcie_type(info.pdev) == PCI_EXP_TYPE_ROOT_PORT;
> +		u16 val = hisi_ptt_get_filter_val(info.pdev);
> +
> +		target_list = is_port ? &hisi_ptt->port_filters : &hisi_ptt->req_filters;
> +
> +		if (info.is_add) {
> +			filter = kzalloc(sizeof(*filter), GFP_KERNEL);
> +			if (!filter)
> +				continue;
> +
> +			filter->pdev = info.pdev;
> +			list_add_tail(&filter->list, target_list);
> +		} else {
> +			list_for_each_entry(filter, target_list, list)
> +				if (hisi_ptt_get_filter_val(filter->pdev) == val) {
> +					list_del(&filter->list);
> +					kfree(filter);
> +					break;
> +				}
> +		}
>  
> -	filter->pdev = pdev;
> -	list_add_tail(&filter->list, target_list);
> +		/* Update the available port mask */
> +		if (!is_port)
> +			continue;
>  
> -	/* Update the available port mask */
> -	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT)
> -		hisi_ptt->port_mask |= hisi_ptt_get_filter_val(pdev);
> +		if (info.is_add)
> +			hisi_ptt->port_mask |= val;
> +		else
> +			hisi_ptt->port_mask &= ~val;
> +	}
> +
> +	mutex_unlock(&hisi_ptt->mutex);
> +}
> +
> +static void hisi_ptt_update_fifo_in(struct hisi_ptt *hisi_ptt,
> +				    struct hisi_ptt_filter_update_info *info)
> +{
> +	struct pci_dev *root_port = pcie_find_root_port(info->pdev);
> +	u32 port_devid;
> +
> +	if (!root_port)
> +		return;
> +
> +	port_devid = PCI_DEVID(root_port->bus->number, root_port->devfn);
> +	if (port_devid < hisi_ptt->lower ||
> +	    port_devid > hisi_ptt->upper)
> +		return;
> +
> +	if (kfifo_in_spinlocked(&hisi_ptt->filter_update_kfifo, info, 1,
> +				&hisi_ptt->filter_update_lock))
> +		schedule_delayed_work(&hisi_ptt->work, 0);
> +	else
> +		pci_warn(hisi_ptt->pdev,
> +			 "filter update fifo overflow for target %s\n",
> +			 pci_name(info->pdev));
> +}
> +
> +/*
> + * A PCI bus notifier is used here for dynamically updating the filter
> + * list.
> + */
> +static int hisi_ptt_notifier_call(struct notifier_block *nb, unsigned long action,
> +				  void *data)
> +{
> +	struct hisi_ptt *hisi_ptt = container_of(nb, struct hisi_ptt, hisi_ptt_nb);
> +	struct hisi_ptt_filter_update_info info;
> +	struct device *dev = data;
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +
> +	info.pdev = pdev;
> +
> +	switch (action) {
> +	case BUS_NOTIFY_ADD_DEVICE:
> +		info.is_add = true;
> +		break;
> +	case BUS_NOTIFY_DEL_DEVICE:
> +		info.is_add = false;
> +		break;
> +	default:
> +		return 0;
> +	}
> +
> +	hisi_ptt_update_fifo_in(hisi_ptt, &info);
> +
> +	return 0;
> +}
> +
> +static int hisi_ptt_init_filters(struct pci_dev *pdev, void *data)
> +{
> +	struct hisi_ptt_filter_update_info info = {
> +		.pdev = pdev,
> +		.is_add = true,
> +	};
> +	struct hisi_ptt *hisi_ptt = data;
> +
> +	hisi_ptt_update_fifo_in(hisi_ptt, &info);
>  
>  	return 0;
>  }
> @@ -316,6 +409,9 @@ static int hisi_ptt_init_ctrls(struct hisi_ptt *hisi_ptt)
>  	int ret;
>  	u32 reg;
>  
> +	INIT_DELAYED_WORK(&hisi_ptt->work, hisi_ptt_update_filters);
> +	spin_lock_init(&hisi_ptt->filter_update_lock);
> +	INIT_KFIFO(hisi_ptt->filter_update_kfifo);
>  	INIT_LIST_HEAD(&hisi_ptt->port_filters);
>  	INIT_LIST_HEAD(&hisi_ptt->req_filters);
>  
> @@ -333,9 +429,11 @@ static int hisi_ptt_init_ctrls(struct hisi_ptt *hisi_ptt)
>  	hisi_ptt->lower = FIELD_GET(HISI_PTT_DEVICE_RANGE_LOWER, reg);
>  
>  	/*
> -	 * hisi_ptt_init_filters() only fails when the memory allocation failed.
> -	 * We don't check the failure here as it won't fail after adding the
> -	 * support of dynamically updating the filters in the following patch.
> +	 * No need to fail if the bus is NULL here as the device
> +	 * maybe hotplugged after the PTT driver probe, in which
> +	 * case we can detect the event and update the list as
> +	 * we register a bus notifier for dynamically updating
> +	 * the filter list.
>  	 */
>  	bus = pci_find_bus(pci_domain_nr(pdev->bus), PCI_BUS_NUM(hisi_ptt->upper));
>  	if (bus)
> @@ -763,6 +861,31 @@ static int hisi_ptt_register_pmu(struct hisi_ptt *hisi_ptt)
>  	return perf_pmu_register(&hisi_ptt->hisi_ptt_pmu, pmu_name, -1);
>  }
>  
> +static void hisi_ptt_unregister_filter_update_notifier(void *data)
> +{
> +	struct hisi_ptt *hisi_ptt = data;
> +
> +	bus_unregister_notifier(&pci_bus_type, &hisi_ptt->hisi_ptt_nb);
> +
> +	/* Cancel any work that has been queued */
> +	cancel_delayed_work_sync(&hisi_ptt->work);
> +}
> +
> +/* Register the bus notifier for dynamically updating the filter list */
> +static int hisi_ptt_register_filter_update_notifier(struct hisi_ptt *hisi_ptt)
> +{
> +	int ret;
> +
> +	hisi_ptt->hisi_ptt_nb.notifier_call = hisi_ptt_notifier_call;
> +	ret = bus_register_notifier(&pci_bus_type, &hisi_ptt->hisi_ptt_nb);
> +	if (ret)
> +		return ret;
> +
> +	return devm_add_action_or_reset(&hisi_ptt->pdev->dev,
> +					hisi_ptt_unregister_filter_update_notifier,
> +					hisi_ptt);
> +}
> +
>  /*
>   * The DMA of PTT trace can only use direct mapping, due to some
>   * hardware restriction. Check whether there is an IOMMU or the
> @@ -835,6 +958,10 @@ static int hisi_ptt_probe(struct pci_dev *pdev,
>  		return ret;
>  	}
>  
> +	ret = hisi_ptt_register_filter_update_notifier(hisi_ptt);
> +	if (ret)
> +		pci_warn(pdev, "failed to register filter update notifier, ret = %d", ret);
> +
>  	ret = hisi_ptt_register_pmu(hisi_ptt);
>  	if (ret) {
>  		pci_err(pdev, "failed to register pmu device, ret = %d", ret);
> diff --git a/drivers/hwtracing/ptt/hisi_ptt.h b/drivers/hwtracing/ptt/hisi_ptt.h
> index 29b6d6293d6c..53805f6c9bc2 100644
> --- a/drivers/hwtracing/ptt/hisi_ptt.h
> +++ b/drivers/hwtracing/ptt/hisi_ptt.h
> @@ -10,11 +10,15 @@
>  #define _HISI_PTT_H
>  
>  #include <linux/bits.h>
> +#include <linux/kfifo.h>
>  #include <linux/list.h>
>  #include <linux/mutex.h>
> +#include <linux/notifier.h>
>  #include <linux/pci.h>
>  #include <linux/perf_event.h>
> +#include <linux/spinlock.h>
>  #include <linux/types.h>
> +#include <linux/workqueue.h>
>  
>  #define DRV_NAME "hisi_ptt"
>  
> @@ -57,6 +61,12 @@
>  /* Wait time for hardware DMA to reset */
>  #define HISI_PTT_RESET_TIMEOUT_US	10UL
>  #define HISI_PTT_RESET_POLL_INTERVAL_US	1UL
> +/* FIFO size for dynamically updating the PTT trace filter list. */
> +#define HISI_PTT_FILTER_UPDATE_FIFO_SIZE	16
> +/* Delay time for filter updating work */
> +#define HISI_PTT_WORK_DELAY_MS		100UL
> +/* Wait time for DMA hardware to reset */
> +#define HISI_PTT_RESET_WAIT_MS		1000UL
>  /* Poll timeout and interval for waiting hardware work to finish */
>  #define HISI_PTT_WAIT_TRACE_TIMEOUT_US	100UL
>  #define HISI_PTT_WAIT_POLL_INTERVAL_US	10UL
> @@ -112,6 +122,15 @@ struct hisi_ptt_filter_desc {
>  	struct pci_dev *pdev;
>  };
>  
> +/**
> + * struct hisi_ptt_filter_update_info - information for PTT filter updating
> + * @pdev:       the PCI device to update in the filter list
> + * @is_add:     adding to the filter or not
> + */
> +struct hisi_ptt_filter_update_info {
> +	struct pci_dev *pdev;
> +	bool is_add;
> +};
>  
>  /**
>   * struct hisi_ptt_pmu_buf - descriptor of the AUX buffer of PTT trace
> @@ -139,9 +158,13 @@ struct hisi_ptt_pmu_buf {
>   * @port_filters: the filter list of root ports
>   * @req_filters:  the filter list of requester ID
>   * @port_mask:    port mask of the managed root ports
> + * @work:         delayed work for filter updating
> + * @filter_update_lock: spinlock to protect the filter update fifo
> + * @filter_update_fifo: fifo of the filters waiting to update the filter list
>   */
>  struct hisi_ptt {
>  	struct hisi_ptt_trace_ctrl trace_ctrl;
> +	struct notifier_block hisi_ptt_nb;
>  	struct pmu hisi_ptt_pmu;
>  	void __iomem *iobase;
>  	struct pci_dev *pdev;
> @@ -159,6 +182,17 @@ struct hisi_ptt {
>  	struct list_head port_filters;
>  	struct list_head req_filters;
>  	u16 port_mask;
> +
> +	/*
> +	 * We use a delayed work here to avoid indefinitely waiting for
> +	 * the hisi_ptt->mutex which protecting the filter list. The
> +	 * work will be delayed only if the mutex can not be held,
> +	 * otherwise no delay will be applied.
> +	 */
> +	struct delayed_work work;
> +	spinlock_t filter_update_lock;
> +	DECLARE_KFIFO(filter_update_kfifo, struct hisi_ptt_filter_update_info,
> +		      HISI_PTT_FILTER_UPDATE_FIFO_SIZE);
>  };
>  
>  #define to_hisi_ptt(pmu) container_of(pmu, struct hisi_ptt, hisi_ptt_pmu)

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