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Message-ID: <f6e5dcda-76a0-10f5-a370-2d27b0ed76b6@linux.intel.com>
Date: Wed, 7 Aug 2024 11:09:57 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Alistair Francis <alistair23@...il.com>
cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
Jonathan.Cameron@...wei.com, Lukas Wunner <lukas@...ner.de>,
alex.williamson@...hat.com, christian.koenig@....com, kch@...dia.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, logang@...tatee.com,
LKML <linux-kernel@...r.kernel.org>, chaitanyak@...dia.com,
rdunlap@...radead.org, Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v15 3/4] PCI/DOE: Expose the DOE features via sysfs
On Wed, 7 Aug 2024, Alistair Francis wrote:
> The PCIe 6 specification added support for the Data Object
> Exchange (DOE).
> When DOE is supported the DOE Discovery Feature must be implemented per
> PCIe r6.1 sec 6.30.1.1. The protocol allows a requester to obtain
> information about the other DOE features supported by the device.
>
> The kernel is already querying the DOE features supported and cacheing
> the values. Expose the values in sysfs to allow user space to
> determine which DOE features are supported by the PCIe device.
>
> By exposing the information to userspace tools like lspci can relay the
> information to users. By listing all of the supported features we can
> allow userspace to parse the list, which might include
> vendor specific features as well as yet to be supported features.
>
> As the DOE Discovery feature must always be supported we treat it as a
> special named attribute case. This allows the usual PCI attribute_group
> handling to correctly create the doe_features directory when registering
> pci_doe_sysfs_group (otherwise it doesn't and sysfs_add_file_to_group()
> will seg fault).
>
> After this patch is supported you can see something like this when
> attaching a DOE device
>
> $ ls /sys/devices/pci0000:00/0000:00:02.0//doe*
> 0001:01 0001:02 doe_discovery
>
> Signed-off-by: Alistair Francis <alistair.francis@....com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
> Using dev->groups and device_add() path as discussed earlier [1]
> doesn't work nicley as the pci_doe_sysfs_group is global.
>
> We end up needing to create a per device instance of dev->groups
> that is dynamically modified at init and appended to pci_dev_attr_groups.
>
> Something similar to:
> https://elixir.bootlin.com/linux/latest/source/drivers/iio/industrialio-core.c#L2029
> except in this case groups is already assigned.
>
> It's complex and doesn't provide any advantages compared to the approach
> in this patch, where we can just use sysfs_add_file_to_group() to add
> the sysfs attributes. This aligns with other PCIe DOE related sysfs
> patches, such as [2]
>
> 1: https://lore.kernel.org/all/20231019165829.GA1381099@bhelgaas/
> 2: https://lore.kernel.org/all/77f549685f994981c010aebb1e9057aa3555b18a.1719771133.git.lukas@wunner.de/
>
> v15:
> - Move init/teardown from pci_{create,remove}_resource_files()
> - Remove `if (IS_ENABLED(CONFIG_PCI_DOE))` checks
> v14:
> - Revert back to v12 with extra pci_remove_resource_files() call
> v13:
> - Drop pci_doe_sysfs_init() and use pci_doe_sysfs_group
> - As discussed in https://lore.kernel.org/all/20231019165829.GA1381099@bhelgaas/
> we can just modify pci_doe_sysfs_group at the DOE init and let
> device_add() handle the sysfs attributes.
> v12:
> - Drop pci_doe_features_sysfs_attr_visible()
> v11:
> - Gracefully handle multiple entried of same feature
> - Minor fixes and code cleanups
> v10:
> - Rebase to use DEFINE_SYSFS_GROUP_VISIBLE and remove
> special setup function
> v9:
> - Add a teardown function
> - Rename functions to be clearer
> - Tidy up the commit message
> - Remove #ifdef from header
> v8:
> - Inlucde an example in the docs
> - Fixup removing a file that wasn't added
> - Remove a blank line
> v7:
> - Fixup the #ifdefs to keep the test robot happy
> v6:
> - Use "feature" instead of protocol
> - Don't use any devm_* functions
> - Add two more patches to the series
> v5:
> - Return the file name as the file contents
> - Code cleanups and simplifications
> v4:
> - Fixup typos in the documentation
> - Make it clear that the file names contain the information
> - Small code cleanups
> - Remove most #ifdefs
> - Remove extra NULL assignment
> v3:
> - Expose each DOE feature as a separate file
> v2:
> - Add documentation
> - Code cleanups
>
> Documentation/ABI/testing/sysfs-bus-pci | 28 +++++
> drivers/pci/doe.c | 144 ++++++++++++++++++++++++
> drivers/pci/pci-sysfs.c | 3 +
> drivers/pci/pci.h | 9 ++
> drivers/pci/probe.c | 3 +
> drivers/pci/remove.c | 2 +
> 6 files changed, 189 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index ecf47559f495..65a3238ab701 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -500,3 +500,31 @@ Description:
> console drivers from the device. Raw users of pci-sysfs
> resourceN attributes must be terminated prior to resizing.
> Success of the resizing operation is not guaranteed.
> +
> +What: /sys/bus/pci/devices/.../doe_features
> +Date: May 2024
> +Contact: Linux PCI developers <linux-pci@...r.kernel.org>
> +Description:
> + This directory contains a list of the supported
> + Data Object Exchange (DOE) features. The features are
> + the file name. The contents of each file is the raw vendor id and
> + data object feature values.
> +
> + The value comes from the device and specifies the vendor and
> + data object type supported. The lower (RHS of the colon) is
> + the data object type in hex. The upper (LHS of the colon)
> + is the vendor ID.
> +
> + As all DOE devices must support the DOE discovery protocol, if
> + DOE is supported you will at least see the doe_discovery file, with
> + this contents
> +
> + # cat doe_features/doe_discovery
> + 0001:00
> +
> + If the device supports other protocols you will see other files
> + as well. For example is CMA/SPDM and secure CMA/SPDM are supported
> + the doe_features directory will look like this
> +
> + # ls doe_features
> + 0001:01 0001:02 doe_discovery
> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> index defc4be81bd4..c0e1ed3bddfb 100644
> --- a/drivers/pci/doe.c
> +++ b/drivers/pci/doe.c
> @@ -14,6 +14,7 @@
>
> #include <linux/bitfield.h>
> #include <linux/delay.h>
> +#include <linux/device.h>
> #include <linux/jiffies.h>
> #include <linux/mutex.h>
> #include <linux/pci.h>
+ #include <linux/sysfs.h>
--
i.
> @@ -47,6 +48,7 @@
> * @wq: Wait queue for work item
> * @work_queue: Queue of pci_doe_work items
> * @flags: Bit array of PCI_DOE_FLAG_* flags
> + * @sysfs_attrs: Array of sysfs device attributes
> */
> struct pci_doe_mb {
> struct pci_dev *pdev;
> @@ -56,6 +58,10 @@ struct pci_doe_mb {
> wait_queue_head_t wq;
> struct workqueue_struct *work_queue;
> unsigned long flags;
> +
> +#ifdef CONFIG_SYSFS
> + struct device_attribute *sysfs_attrs;
> +#endif
> };
>
> struct pci_doe_feature {
> @@ -92,6 +98,144 @@ struct pci_doe_task {
> struct pci_doe_mb *doe_mb;
> };
>
> +#ifdef CONFIG_SYSFS
> +static ssize_t doe_discovery_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + return sysfs_emit(buf, "0001:00\n");
> +}
> +DEVICE_ATTR_RO(doe_discovery);
> +
> +static struct attribute *pci_doe_sysfs_feature_attrs[] = {
> + &dev_attr_doe_discovery.attr,
> + NULL
> +};
> +
> +static bool pci_doe_features_sysfs_group_visible(struct kobject *kobj)
> +{
> + struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
> +
> + return !xa_empty(&pdev->doe_mbs);
> +}
> +DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE(pci_doe_features_sysfs)
> +
> +const struct attribute_group pci_doe_sysfs_group = {
> + .name = "doe_features",
> + .attrs = pci_doe_sysfs_feature_attrs,
> + .is_visible = SYSFS_GROUP_VISIBLE(pci_doe_features_sysfs),
> +};
> +
> +static ssize_t pci_doe_sysfs_feature_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + return sysfs_emit(buf, "%s\n", attr->attr.name);
> +}
> +
> +static void pci_doe_sysfs_feature_remove(struct pci_dev *pdev,
> + struct pci_doe_mb *doe_mb)
> +{
> + struct device_attribute *attrs = doe_mb->sysfs_attrs;
> + struct device *dev = &pdev->dev;
> + unsigned long i;
> + void *entry;
> +
> + if (!attrs)
> + return;
> +
> + doe_mb->sysfs_attrs = NULL;
> + xa_for_each(&doe_mb->feats, i, entry) {
> + if (attrs[i].show)
> + sysfs_remove_file_from_group(&dev->kobj, &attrs[i].attr,
> + pci_doe_sysfs_group.name);
> + kfree(attrs[i].attr.name);
> + }
> + kfree(attrs);
> +}
> +
> +static int pci_doe_sysfs_feature_populate(struct pci_dev *pdev,
> + struct pci_doe_mb *doe_mb)
> +{
> + struct device *dev = &pdev->dev;
> + struct device_attribute *attrs;
> + unsigned long num_features = 0;
> + unsigned long vid, type;
> + unsigned long i;
> + void *entry;
> + int ret;
> +
> + xa_for_each(&doe_mb->feats, i, entry)
> + num_features++;
> +
> + attrs = kcalloc(num_features, sizeof(*attrs), GFP_KERNEL);
> + if (!attrs)
> + return -ENOMEM;
> +
> + doe_mb->sysfs_attrs = attrs;
> + xa_for_each(&doe_mb->feats, i, entry) {
> + sysfs_attr_init(&attrs[i].attr);
> + vid = xa_to_value(entry) >> 8;
> + type = xa_to_value(entry) & 0xFF;
> +
> + if (vid == PCI_VENDOR_ID_PCI_SIG && type == PCI_DOE_FEATURE_DISCOVERY) {
> + /* DOE Discovery, manually displayed by `dev_attr_doe_discovery` */
> + continue;
> + }
> +
> + attrs[i].attr.name = kasprintf(GFP_KERNEL,
> + "%04lx:%02lx", vid, type);
> + if (!attrs[i].attr.name) {
> + ret = -ENOMEM;
> + goto fail;
> + }
> +
> + attrs[i].attr.mode = 0444;
> + attrs[i].show = pci_doe_sysfs_feature_show;
> +
> + ret = sysfs_add_file_to_group(&dev->kobj, &attrs[i].attr,
> + pci_doe_sysfs_group.name);
> + if (ret) {
> + attrs[i].show = NULL;
> + if (ret != -EEXIST)
> + goto fail;
> + else
> + kfree(attrs[i].attr.name);
> + }
> + }
> +
> + return 0;
> +
> +fail:
> + pci_doe_sysfs_feature_remove(pdev, doe_mb);
> + return ret;
> +}
> +
> +void pci_doe_sysfs_teardown(struct pci_dev *pdev)
> +{
> + struct pci_doe_mb *doe_mb;
> + unsigned long index;
> +
> + xa_for_each(&pdev->doe_mbs, index, doe_mb)
> + pci_doe_sysfs_feature_remove(pdev, doe_mb);
> +}
> +
> +int pci_doe_sysfs_init(struct pci_dev *pdev)
> +{
> + struct pci_doe_mb *doe_mb;
> + unsigned long index;
> + int ret;
> +
> + xa_for_each(&pdev->doe_mbs, index, doe_mb) {
> + ret = pci_doe_sysfs_feature_populate(pdev, doe_mb);
> + if (ret)
> + return ret;
> + }
> +
> + return 0;
> +}
> +#endif
> +
> static int pci_doe_wait(struct pci_doe_mb *doe_mb, unsigned long timeout)
> {
> if (wait_event_timeout(doe_mb->wq,
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 40cfa716392f..eeda0c650537 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1661,6 +1661,9 @@ const struct attribute_group *pci_dev_attr_groups[] = {
> #endif
> #ifdef CONFIG_PCIEASPM
> &aspm_ctrl_attr_group,
> +#endif
> +#ifdef CONFIG_PCI_DOE
> + &pci_doe_sysfs_group,
> #endif
> NULL,
> };
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 79c8398f3938..abac97efc8fc 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -232,6 +232,7 @@ extern const struct attribute_group *pci_dev_groups[];
> extern const struct attribute_group *pci_dev_attr_groups[];
> extern const struct attribute_group *pcibus_groups[];
> extern const struct attribute_group *pci_bus_groups[];
> +extern const struct attribute_group pci_doe_sysfs_group;
> #else
> static inline int pci_create_sysfs_dev_files(struct pci_dev *pdev) { return 0; }
> static inline void pci_remove_sysfs_dev_files(struct pci_dev *pdev) { }
> @@ -398,6 +399,14 @@ static inline void pci_doe_destroy(struct pci_dev *pdev) { }
> static inline void pci_doe_disconnected(struct pci_dev *pdev) { }
> #endif
>
> +#if defined(CONFIG_PCI_DOE) && defined(CONFIG_SYSFS)
> +int pci_doe_sysfs_init(struct pci_dev *pci_dev);
> +void pci_doe_sysfs_teardown(struct pci_dev *pdev);
> +#else
> +static inline int pci_doe_sysfs_init(struct pci_dev *pdev) { return 0; }
> +static inline void pci_doe_sysfs_teardown(struct pci_dev *pdev) { }
> +#endif
> +
> /**
> * pci_dev_set_io_state - Set the new error state if possible.
> *
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index b14b9876c030..2bdb4fe37dbc 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2593,6 +2593,9 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
> dev->match_driver = false;
> ret = device_add(&dev->dev);
> WARN_ON(ret < 0);
> +
> + ret = pci_doe_sysfs_init(dev);
> + WARN_ON(ret < 0);
> }
>
> struct pci_dev *pci_scan_single_device(struct pci_bus *bus, int devfn)
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index 910387e5bdbf..d1e0bed53acb 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -34,6 +34,8 @@ static void pci_destroy_dev(struct pci_dev *dev)
> if (!dev->dev.kobj.parent)
> return;
>
> + pci_doe_sysfs_teardown(dev);
> +
> device_del(&dev->dev);
>
> down_write(&pci_bus_sem);
>
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