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Message-ID: <b986eb03-0887-4eb2-a7a7-50ef63e51096@oss.qualcomm.com>
Date: Thu, 8 Jan 2026 15:36:45 -0700
From: Zack McKevitt <zachary.mckevitt@....qualcomm.com>
To: Rodrigo Vivi <rodrigo.vivi@...el.com>,
Riana Tauro
<riana.tauro@...el.com>, Jakub Kicinski <kuba@...nel.org>
Cc: intel-xe@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
aravind.iddamsetty@...ux.intel.com, anshuman.gupta@...el.com,
joonas.lahtinen@...ux.intel.com, lukas@...ner.de,
simona.vetter@...ll.ch, airlied@...il.com, pratik.bari@...el.com,
joshua.santosh.ranjan@...el.com, ashwin.kumar.kulkarni@...el.com,
shubham.kumar@...el.com, Lijo Lazar <lijo.lazar@....com>,
Hawking Zhang <Hawking.Zhang@....com>,
"David S. Miller" <davem@...emloft.net>,
Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>,
netdev@...r.kernel.org
Subject: Re: [PATCH v3 1/4] drm/ras: Introduce the DRM RAS infrastructure over
generic netlink
On 12/9/2025 2:35 PM, Rodrigo Vivi wrote:
Apologies for the delay getting back to this. We are still supportive of
this functionality making it into the DRM subsystem but have a couple of
questions.
> On Fri, Dec 05, 2025 at 02:09:33PM +0530, Riana Tauro wrote:
>> From: Rodrigo Vivi <rodrigo.vivi@...el.com>
>>
>> Introduces the DRM RAS infrastructure over generic netlink.
>>
>> The new interface allows drivers to expose RAS nodes and their
>> associated error counters to userspace in a structured and extensible
>> way. Each drm_ras node can register its own set of error counters, which
>> are then discoverable and queryable through netlink operations. This
>> lays the groundwork for reporting and managing hardware error states
>> in a unified manner across different DRM drivers.
>>
>> Currently is only supports error-counter nodes. But it can be
>> extended later.
>>
>> The registration is also no tied to any drm node, so it can be
>> used by accel devices as well.
Thank you for including the userspace reference implementation. I have
begun prototyping an extension for our qaic accel driver to incorporate
telemetry functionality by adding a new node type to drm_ras. Overall,
extending the interface is intuitive.
>>
>> It uses the new and mandatory YAML description format stored in
>> Documentation/netlink/specs/. This forces a single generic netlink
>> family namespace for the entire drm: "drm-ras".
>> But multiple-endpoints are supported within the single family.
>>
>> Any modification to this API needs to be applied to
>> Documentation/netlink/specs/drm_ras.yaml before regenerating the
>> code:
>>
>> $ tools/net/ynl/pyynl/ynl_gen_c.py --spec \
>> Documentation/netlink/specs/drm_ras.yaml --mode uapi --header \
>> > include/uapi/drm/drm_ras.h
>>
>> $ tools/net/ynl/pyynl/ynl_gen_c.py --spec \
>> Documentation/netlink/specs/drm_ras.yaml --mode kernel --header \
>> > include/drm/drm_ras_nl.h
>>
>> $ tools/net/ynl/pyynl/ynl_gen_c.py --spec \
>> Documentation/netlink/specs/drm_ras.yaml --mode kernel --source \
>> > drivers/gpu/drm/drm_ras_nl.c
>>
>> Cc: Zack McKevitt <zachary.mckevitt@....qualcomm.com>
>> Cc: Lukas Wunner <lukas@...ner.de>
>> Cc: Lijo Lazar <lijo.lazar@....com>
>> Cc: Hawking Zhang <Hawking.Zhang@....com>
>> Cc: Jakub Kicinski <kuba@...nel.org>
>> Cc: David S. Miller <davem@...emloft.net>
>> Cc: Paolo Abeni <pabeni@...hat.com>
>> Cc: Eric Dumazet <edumazet@...gle.com>
>> Cc: netdev@...r.kernel.org
>> Co-developed-by: Aravind Iddamsetty <aravind.iddamsetty@...ux.intel.com>
>> Signed-off-by: Aravind Iddamsetty <aravind.iddamsetty@...ux.intel.com>
>> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
>> Signed-off-by: Riana Tauro <riana.tauro@...el.com>
>> ---
>> v2: fix doc and memory leak
>> use xe_for_each_start
>> use standard genlmsg_iput (Jakub Kicinski)
>>
>> v3: add documentation to index
>> modify documentation to mention uAPI requirements (Rodrigo)
>> ---
>> Documentation/gpu/drm-ras.rst | 109 +++++++
>> Documentation/gpu/index.rst | 1 +
>> Documentation/netlink/specs/drm_ras.yaml | 130 +++++++++
>> drivers/gpu/drm/Kconfig | 9 +
>> drivers/gpu/drm/Makefile | 1 +
>> drivers/gpu/drm/drm_drv.c | 6 +
>> drivers/gpu/drm/drm_ras.c | 351 +++++++++++++++++++++++
>> drivers/gpu/drm/drm_ras_genl_family.c | 42 +++
>> drivers/gpu/drm/drm_ras_nl.c | 54 ++++
>> include/drm/drm_ras.h | 76 +++++
>> include/drm/drm_ras_genl_family.h | 17 ++
>> include/drm/drm_ras_nl.h | 24 ++
>> include/uapi/drm/drm_ras.h | 49 ++++
>> 13 files changed, 869 insertions(+)
>> create mode 100644 Documentation/gpu/drm-ras.rst
>> create mode 100644 Documentation/netlink/specs/drm_ras.yaml
>> create mode 100644 drivers/gpu/drm/drm_ras.c
>> create mode 100644 drivers/gpu/drm/drm_ras_genl_family.c
>> create mode 100644 drivers/gpu/drm/drm_ras_nl.c
>> create mode 100644 include/drm/drm_ras.h
>> create mode 100644 include/drm/drm_ras_genl_family.h
>> create mode 100644 include/drm/drm_ras_nl.h
>> create mode 100644 include/uapi/drm/drm_ras.h
>>
>> diff --git a/Documentation/gpu/drm-ras.rst b/Documentation/gpu/drm-ras.rst
>> new file mode 100644
>> index 000000000000..cec60cf5d17d
>> --- /dev/null
>> +++ b/Documentation/gpu/drm-ras.rst
>> @@ -0,0 +1,109 @@
>> +.. SPDX-License-Identifier: GPL-2.0+
>> +
>> +============================
>> +DRM RAS over Generic Netlink
>> +============================
>> +
>> +The DRM RAS (Reliability, Availability, Serviceability) interface provides a
>> +standardized way for GPU/accelerator drivers to expose error counters and
>> +other reliability nodes to user space via Generic Netlink. This allows
>> +diagnostic tools, monitoring daemons, or test infrastructure to query hardware
>> +health in a uniform way across different DRM drivers.
>> +
>> +Key Goals:
>> +
>> +* Provide a standardized RAS solution for GPU and accelerator drivers, enabling
>> + data center monitoring and reliability operations.
>> +* Implement a single drm-ras Generic Netlink family to meet modern Netlink YAML
>> + specifications and centralize all RAS-related communication in one namespace.
>> +* Support a basic error counter interface, addressing the immediate, essential
>> + monitoring needs.
>> +* Offer a flexible, future-proof interface that can be extended to support
>> + additional types of RAS data in the future.
>> +* Allow multiple nodes per driver, enabling drivers to register separate
>> + nodes for different IP blocks, sub-blocks, or other logical subdivisions
>> + as applicable.
>> +
>> +Nodes
>> +=====
>> +
>> +Nodes are logical abstractions representing an error source or block within
>> +the device. Currently, only error counter nodes is supported.
>> +
>> +Drivers are responsible for registering and unregistering nodes via the
>> +`drm_ras_node_register()` and `drm_ras_node_unregister()` APIs.
>> +
>> +Node Management
>> +-------------------
>> +
>> +.. kernel-doc:: drivers/gpu/drm/drm_ras.c
>> + :doc: DRM RAS Node Management
>> +.. kernel-doc:: drivers/gpu/drm/drm_ras.c
>> + :internal:
>> +
>> +Generic Netlink Usage
>> +=====================
>> +
>> +The interface is implemented as a Generic Netlink family named ``drm-ras``.
>> +User space tools can:
>> +
>> +* List registered nodes with the ``get-nodes`` command.
>> +* List all error counters in an node with the ``get-error-counters`` command.
>> +* Query error counters using the ``query-error-counter`` command.
>> +
>> +YAML-based Interface
>> +--------------------
>> +
>> +The interface is described in a YAML specification:
>> +
>> +:ref:`Documentation/netlink/specs/drm_ras.yaml`
>> +
>> +This YAML is used to auto-generate user space bindings via
>> +``tools/net/ynl/pyynl/ynl_gen_c.py``, and drives the structure of netlink
>> +attributes and operations.
>> +
>> +Usage Notes
>> +-----------
>> +
>> +* User space must first enumerate nodes to obtain their IDs.
>> +* Node IDs or Node names can be used for all further queries, such as error counters.
>> +* Error counters can be queried by either the Error ID or Error name.
>> +* Query Parameters should be defined as part of the uAPI to ensure user interface stability.
>> +* The interface supports future extension by adding new node types and
>> + additional attributes.
>> +
>> +Example: List nodes using ynl
>> +
>> +.. code-block:: bash
>> +
>> + sudo ynl --family drm_ras --dump list-nodes
>> + [{'device-name': '0000:03:00.0',
>> + 'node-id': 0,
>> + 'node-name': 'correctable-errors',
>> + 'node-type': 'error-counter'},
>> + {'device-name': '0000:03:00.0',
>> + 'node-id': 1,
>> + 'node-name': 'nonfatal-errors',
>> + 'node-type': 'error-counter'},
>> + {'device-name': '0000:03:00.0',
>> + 'node-id': 2,
>> + 'node-name': 'fatal-errors',
>> + 'node-type': 'error-counter'}]
>> +
>> +Example: List all error counters using ynl
>> +
>> +.. code-block:: bash
>> +
>> +
>> + sudo ynl --family drm_ras --dump get-error-counters --json '{"node-id":1}'
>> + [{'error-id': 1, 'error-name': 'error_name_1', 'error-value': 0},
>> + {'error-id': 2, 'error-name': 'error_name_2', 'error-value': 0}]
>> +
>> +
>> +Example: Query an error counter for a given node
>> +
>> +.. code-block:: bash
>> +
>> + sudo ynl --family drm_ras --do query-error-counter --json '{"node-id":2, "error-id":1}'
>> + {'error-id': 1, 'error-name': 'error_name_1', 'error-value': 0}
>> +
>> diff --git a/Documentation/gpu/index.rst b/Documentation/gpu/index.rst
>> index 7dcb15850afd..60c73fdcfeed 100644
>> --- a/Documentation/gpu/index.rst
>> +++ b/Documentation/gpu/index.rst
>> @@ -9,6 +9,7 @@ GPU Driver Developer's Guide
>> drm-mm
>> drm-kms
>> drm-kms-helpers
>> + drm-ras
>> drm-uapi
>> drm-usage-stats
>> driver-uapi
>> diff --git a/Documentation/netlink/specs/drm_ras.yaml b/Documentation/netlink/specs/drm_ras.yaml
>> new file mode 100644
>> index 000000000000..be0e379c5bc9
>> --- /dev/null
>> +++ b/Documentation/netlink/specs/drm_ras.yaml
>> @@ -0,0 +1,130 @@
>> +# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
>> +---
>> +name: drm-ras
>> +protocol: genetlink
>> +uapi-header: drm/drm_ras.h
>> +
>> +doc: >-
>> + DRM RAS (Reliability, Availability, Serviceability) over Generic Netlink.
>> + Provides a standardized mechanism for DRM drivers to register "nodes"
>> + representing hardware/software components capable of reporting error counters.
>> + Userspace tools can query the list of nodes or individual error counters
>> + via the Generic Netlink interface.
>> +
>> +definitions:
>> + -
>> + type: enum
>> + name: node-type
>> + value-start: 1
>> + entries: [error-counter]
>> + doc: >-
>> + Type of the node. Currently, only error-counter nodes are
>> + supported, which expose reliability counters for a hardware/software
>> + component.
>> +
>> +attribute-sets:
>> + -
>> + name: node-attrs
>> + attributes:
>> + -
>> + name: node-id
>> + type: u32
>> + doc: >-
>> + Unique identifier for the node.
>> + Assigned dynamically by the DRM RAS core upon registration.
>> + -
>> + name: device-name
>> + type: string
>> + doc: >-
>> + Device name chosen by the driver at registration.
>> + Can be a PCI BDF, UUID, or module name if unique.
>> + -
>> + name: node-name
>> + type: string
>> + doc: >-
>> + Node name chosen by the driver at registration.
>> + Can be an IP block name, or any name that identifies the
>> + RAS node inside the device.
>> + -
>> + name: node-type
>> + type: u32
>> + doc: Type of this node, identifying its function.
>> + enum: node-type
>> + -
>> + name: error-counter-attrs
>> + attributes:
>> + -
>> + name: node-id
>> + type: u32
>> + doc: Node ID targeted by this error counter operation.
>> + -
>> + name: error-id
>> + type: u32
>> + doc: Unique identifier for a specific error counter within an node.
>> + -
>> + name: error-name
>> + type: string
>> + doc: Name of the error.
>> + -
>> + name: error-value
>> + type: u32
>> + doc: Current value of the requested error counter.
>> +
>> +operations:
>> + list:
>> + -
>> + name: list-nodes
>> + doc: >-
>> + Retrieve the full list of currently registered DRM RAS nodes.
>> + Each node includes its dynamically assigned ID, name, and type.
>> + **Important:** User space must call this operation first to obtain
>> + the node IDs. These IDs are required for all subsequent
>> + operations on nodes, such as querying error counters.
I am curious about security implications of this design. If the complete
list of RAS nodes is visible for any process on the system (and one
wants to avoid requiring CAP_NET_ADMIN), there should be some way to
enforce permission checks when performing these operations if desired.
For example, this might be implemented in the driver's definition of
callback functions like query_error_counter; some drivers may want to
ensure that the process can in fact open the file descriptor
corresponding to the queried device before serving a netlink request. Is
it enough for a driver to simply return -EPERM in this case? Any driver
that doesnt wish to protect its RAS nodes need not implement checks in
their callbacks.
I dont see any such permissions checks in your driver implementation
which is understandable given that it may not be necessary for your use
cases. However, this would be a concern for our driver if we were to
adopt this interface.
>> + attribute-set: node-attrs
>> + flags: [admin-perm]
>> + dump:
>> + reply:
>> + attributes:
>> + - node-id
>> + - device-name
>> + - node-name
>> + - node-type
>> + -
>> + name: get-error-counters
>> + doc: >-
>> + Retrieve the full list of error counters for a given node.
>> + The response include the id, the name, and even the current
>> + value of each counter.
>> + attribute-set: error-counter-attrs
>> + flags: [admin-perm]
>> + dump:
>> + request:
>> + attributes:
>> + - node-id
>> + reply:
>> + attributes:
>> + - error-id
>> + - error-name
>> + - error-value
>> + -
>> + name: query-error-counter
>> + doc: >-
>> + Query the information of a specific error counter for a given node.
>> + Users must provide the node ID and the error counter ID.
>> + The response contains the id, the name, and the current value
>> + of the counter.
>> + attribute-set: error-counter-attrs
>> + flags: [admin-perm]
>> + do:
>> + request:
>> + attributes:
>> + - node-id
>> + - error-id
>> + reply:
>> + attributes:
>> + - error-id
>> + - error-name
>> + - error-value
>> +
>> +kernel-family:
>> + headers: ["drm/drm_ras_nl.h"]
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 7e6bc0b3a589..5cfb23b80441 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -130,6 +130,15 @@ config DRM_PANIC_SCREEN_QR_VERSION
>> Smaller QR code are easier to read, but will contain less debugging
>> data. Default is 40.
>>
>> +config DRM_RAS
>> + bool "DRM RAS support"
>> + depends on DRM
>> + help
>> + Enables the DRM RAS (Reliability, Availability and Serviceability)
>> + support for DRM drivers. This provides a Generic Netlink interface
>> + for error reporting and queries.
>> + If in doubt, say "N".
>> +
>> config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
>> bool "Enable refcount backtrace history in the DP MST helpers"
>> depends on STACKTRACE_SUPPORT
>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
>> index 4b3f3ad5058a..cd19573b2d9f 100644
>> --- a/drivers/gpu/drm/Makefile
>> +++ b/drivers/gpu/drm/Makefile
>> @@ -95,6 +95,7 @@ drm-$(CONFIG_DRM_ACCEL) += ../../accel/drm_accel.o
>> drm-$(CONFIG_DRM_PANIC) += drm_panic.o
>> drm-$(CONFIG_DRM_DRAW) += drm_draw.o
>> drm-$(CONFIG_DRM_PANIC_SCREEN_QR_CODE) += drm_panic_qr.o
>> +drm-$(CONFIG_DRM_RAS) += drm_ras.o drm_ras_nl.o drm_ras_genl_family.o
>> obj-$(CONFIG_DRM) += drm.o
>>
>> obj-$(CONFIG_DRM_PANEL_ORIENTATION_QUIRKS) += drm_panel_orientation_quirks.o
>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>> index 2915118436ce..6b965c3d3307 100644
>> --- a/drivers/gpu/drm/drm_drv.c
>> +++ b/drivers/gpu/drm/drm_drv.c
>> @@ -53,6 +53,7 @@
>> #include <drm/drm_panic.h>
>> #include <drm/drm_print.h>
>> #include <drm/drm_privacy_screen_machine.h>
>> +#include <drm/drm_ras_genl_family.h>
>>
>> #include "drm_crtc_internal.h"
>> #include "drm_internal.h"
>> @@ -1223,6 +1224,7 @@ static const struct file_operations drm_stub_fops = {
>>
>> static void drm_core_exit(void)
>> {
>> + drm_ras_genl_family_unregister();
>> drm_privacy_screen_lookup_exit();
>> drm_panic_exit();
>> accel_core_exit();
>> @@ -1261,6 +1263,10 @@ static int __init drm_core_init(void)
>>
>> drm_privacy_screen_lookup_init();
>>
>> + ret = drm_ras_genl_family_register();
>> + if (ret < 0)
>> + goto error;
>> +
>> drm_core_init_complete = true;
>>
>> DRM_DEBUG("Initialized\n");
>> diff --git a/drivers/gpu/drm/drm_ras.c b/drivers/gpu/drm/drm_ras.c
>> new file mode 100644
>> index 000000000000..32f3897ce580
>> --- /dev/null
>> +++ b/drivers/gpu/drm/drm_ras.c
>> @@ -0,0 +1,351 @@
>> +// SPDX-License-Identifier: MIT
>> +/*
>> + * Copyright © 2025 Intel Corporation
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/kernel.h>
>> +#include <linux/netdevice.h>
>> +#include <linux/xarray.h>
>> +#include <net/genetlink.h>
>> +
>> +#include <drm/drm_ras.h>
>> +
>> +/**
>> + * DOC: DRM RAS Node Management
>> + *
>> + * This module provides the infrastructure to manage RAS (Reliability,
>> + * Availability, and Serviceability) nodes for DRM drivers. Each
>> + * DRM driver may register one or more RAS nodes, which represent
>> + * logical components capable of reporting error counters and other
>> + * reliability metrics.
>> + *
>> + * The nodes are stored in a global xarray `drm_ras_xa` to allow
>> + * efficient lookup by ID. Nodes can be registered or unregistered
>> + * dynamically at runtime.
>> + *
>> + * A Generic Netlink family `drm_ras` exposes two main operations to
>> + * userspace:
Nit: Three main operations.
>> + *
>> + * 1. LIST_NODES: Dump all currently registered RAS nodes.
>> + * The user receives an array of node IDs, names, and types.
>> + *
>> + * 2. GET_ERROR_COUNTERS: Dump all error counters of a given node.
>> + * The user receives an array of error IDs, names, and current value.
>> + *
>> + * 3. QUERY_ERROR_COUNTER: Query a specific error counter for a given node.
>> + * Userspace must provide the node ID and the counter ID, and
>> + * receives the ID, the error name, and its current value.
>> + *
>> + * Node registration:
>> + * - drm_ras_node_register(): Registers a new node and assigns
>> + * it a unique ID in the xarray.
>> + * - drm_ras_node_unregister(): Removes a previously registered
>> + * node from the xarray.
>> + *
>> + * Node type:
>> + * - ERROR_COUNTER:
>> + * + Currently, only error counters are supported.
>> + * + The driver must implement the query_error_counter() callback to provide
>> + * the name and the value of the error counter.
>> + * + The driver must provide a error_counter_range.last value informing the
>> + * last valid error ID.
>> + * + The driver can provide a error_counter_range.first value informing the
>> + * frst valid error ID.
>> + * + The error counters in the driver doesn't need to be contiguous, but the
>> + * driver must return -ENOENT to the query_error_counter as an indication
>> + * that the ID should be skipped and not listed in the netlink API.
>> + *
>> + * Netlink handlers:
>> + * - drm_ras_nl_list_nodes_dumpit(): Implements the LIST_NODES
>> + * operation, iterating over the xarray.
>> + * - drm_ras_nl_get_error_counters_dumpit(): Implements the GET_ERROR_COUNTERS
>> + * operation, iterating over the know valid error_counter_range.
>> + * - drm_ras_nl_query_error_counter_doit(): Implements the QUERY_ERROR_COUNTER
>> + * operation, fetching a counter value from a specific node.
>> + */
>> +
>> +static DEFINE_XARRAY_ALLOC(drm_ras_xa);
>> +
>> +/*
>> + * The netlink callback context carries dump state across multiple dumpit calls
>> + */
>> +struct drm_ras_ctx {
>> + /* Which xarray id to restart the dump from */
>> + unsigned long restart;
>> +};
>> +
>> +/**
>> + * drm_ras_nl_list_nodes_dumpit() - Dump all registered RAS nodes
>> + * @skb: Netlink message buffer
>> + * @cb: Callback context for multi-part dumps
>> + *
>> + * Iterates over all registered RAS nodes in the global xarray and appends
>> + * their attributes (ID, name, type) to the given netlink message buffer.
>> + * Uses @cb->ctx to track progress in case the message buffer fills up, allowing
>> + * multi-part dump support. On buffer overflow, updates the context to resume
>> + * from the last node on the next invocation.
>> + *
>> + * Return: 0 if all nodes fit in @skb, number of bytes added to @skb if
>> + * the buffer filled up (requires multi-part continuation), or
>> + * a negative error code on failure.
>> + */
>> +int drm_ras_nl_list_nodes_dumpit(struct sk_buff *skb,
>> + struct netlink_callback *cb)
>> +{
>> + const struct genl_info *info = genl_info_dump(cb);
>> + struct drm_ras_ctx *ctx = (void *)cb->ctx;
>> + struct drm_ras_node *node;
>> + struct nlattr *hdr;
>> + unsigned long id;
>> + int ret;
>> +
>> + xa_for_each_start(&drm_ras_xa, id, node, ctx->restart) {
>> + hdr = genlmsg_iput(skb, info);
>> + if (!hdr) {
>> + ret = -EMSGSIZE;
>> + break;
>> + }
>> +
>> + ret = nla_put_u32(skb, DRM_RAS_A_NODE_ATTRS_NODE_ID, node->id);
>> + if (ret) {
>> + genlmsg_cancel(skb, hdr);
>> + break;
>> + }
>> +
>> + ret = nla_put_string(skb, DRM_RAS_A_NODE_ATTRS_DEVICE_NAME,
>> + node->device_name);
>> + if (ret) {
>> + genlmsg_cancel(skb, hdr);
>> + break;
>> + }
>> +
>> + ret = nla_put_string(skb, DRM_RAS_A_NODE_ATTRS_NODE_NAME,
>> + node->node_name);
>> + if (ret) {
>> + genlmsg_cancel(skb, hdr);
>> + break;
>> + }
>> +
>> + ret = nla_put_u32(skb, DRM_RAS_A_NODE_ATTRS_NODE_TYPE,
>> + node->type);
>> + if (ret) {
>> + genlmsg_cancel(skb, hdr);
>> + break;
>> + }
>> +
>> + genlmsg_end(skb, hdr);
>> + }
>> +
>> + if (ret == -EMSGSIZE)
>> + ctx->restart = id;
>
> Jakub had mentioned that we don't need this special handling
> of the -EMSGSIZE, but then I'm not sure what to use in the
> xa_for_each_start, so
>
> Cc: Jakub Kicinski <kuba@...nel.org>
>
> to ensure that we are in the right path here.
>
> Riana, thank you so much for picking up this and addressing all
> the comments. Patch looks good to me.
>
> Thanks,
> Rodrigo.
>
>> +
>> + return ret;
>> +}
>> +
>> +static int get_node_error_counter(u32 node_id, u32 error_id,
>> + const char **name, u32 *value)
>> +{
>> + struct drm_ras_node *node;
>> +
>> + node = xa_load(&drm_ras_xa, node_id);
>> + if (!node || !node->query_error_counter)
>> + return -ENOENT;
>> +
>> + if (error_id < node->error_counter_range.first ||
>> + error_id > node->error_counter_range.last)
>> + return -EINVAL;
>> +
>> + return node->query_error_counter(node, error_id, name, value);
>> +}
Regarding the permission check, node->query_error_counter could be
implemented to return -EPERM in this case by checking driver specified
fields in node->priv. Thoughts?
>> +
>> +static int msg_reply_value(struct sk_buff *msg, u32 error_id,
>> + const char *error_name, u32 value)
>> +{
>> + int ret;
>> +
>> + ret = nla_put_u32(msg, DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_ID, error_id);
>> + if (ret)
>> + return ret;
>> +
>> + ret = nla_put_string(msg, DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_NAME,
>> + error_name);
>> + if (ret)
>> + return ret;
>> +
>> + return nla_put_u32(msg, DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_VALUE,
>> + value);
>> +}
>> +
>> +static int doit_reply_value(struct genl_info *info, u32 node_id,
>> + u32 error_id)
>> +{
>> + struct sk_buff *msg;
>> + struct nlattr *hdr;
>> + const char *error_name;
>> + u32 value;
>> + int ret;
>> +
>> + msg = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
>> + if (!msg)
>> + return -ENOMEM;
>> +
>> + hdr = genlmsg_iput(msg, info);
>> + if (!hdr) {
>> + nlmsg_free(msg);
>> + return -EMSGSIZE;
>> + }
>> +
>> + ret = get_node_error_counter(node_id, error_id,
>> + &error_name, &value);
>> + if (ret)
>> + return ret;
>> +
>> + ret = msg_reply_value(msg, error_id, error_name, value);
>> + if (ret) {
>> + genlmsg_cancel(msg, hdr);
>> + nlmsg_free(msg);
>> + return ret;
>> + }
>> +
>> + genlmsg_end(msg, hdr);
>> +
>> + return genlmsg_reply(msg, info);
>> +}
>> +
>> +/**
>> + * drm_ras_nl_get_error_counters_dumpit() - Dump all Error Counters
>> + * @skb: Netlink message buffer
>> + * @cb: Callback context for multi-part dumps
>> + *
>> + * Iterates over all error counters in a given Node and appends
>> + * their attributes (ID, name, value) to the given netlink message buffer.
>> + * Uses @cb->ctx to track progress in case the message buffer fills up, allowing
>> + * multi-part dump support. On buffer overflow, updates the context to resume
>> + * from the last node on the next invocation.
>> + *
>> + * Return: 0 if all errors fit in @skb, number of bytes added to @skb if
>> + * the buffer filled up (requires multi-part continuation), or
>> + * a negative error code on failure.
>> + */
>> +int drm_ras_nl_get_error_counters_dumpit(struct sk_buff *skb,
>> + struct netlink_callback *cb)
>> +{
>> + const struct genl_info *info = genl_info_dump(cb);
>> + struct drm_ras_ctx *ctx = (void *)cb->ctx;
>> + struct drm_ras_node *node;
>> + struct nlattr *hdr;
>> + const char *error_name;
>> + u32 node_id, error_id, value;
>> + int ret;
>> +
>> + if (!info->attrs || !info->attrs[DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID])
>> + return -EINVAL;
>> +
>> + node_id = nla_get_u32(info->attrs[DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID]);
>> +
>> + node = xa_load(&drm_ras_xa, node_id);
>> + if (!node)
>> + return -ENOENT;
>> +
>> + for (error_id = max(node->error_counter_range.first, ctx->restart);
>> + error_id <= node->error_counter_range.last;
>> + error_id++) {
>> + ret = get_node_error_counter(node_id, error_id,
>> + &error_name, &value);
>> + /*
>> + * For non-contiguous range, driver return -ENOENT as indication
>> + * to skip this ID when listing all errors.
>> + */
>> + if (ret == -ENOENT)
>> + continue;
>> + if (ret)
>> + return ret;
>> +
>> + hdr = genlmsg_iput(skb, info);
>> +
>> + if (!hdr) {
>> + ret = -EMSGSIZE;
>> + break;
>> + }
>> +
>> + ret = msg_reply_value(skb, error_id, error_name, value);
>> + if (ret) {
>> + genlmsg_cancel(skb, hdr);
>> + break;
>> + }
>> +
>> + genlmsg_end(skb, hdr);
>> + }
>> +
>> + if (ret == -EMSGSIZE)
>> + ctx->restart = error_id;
>> +
>> + return ret;
>> +}
>> +
>> +/**
>> + * drm_ras_nl_query_error_counter_doit() - Query an error counter of an node
>> + * @skb: Netlink message buffer
>> + * @info: Generic Netlink info containing attributes of the request
>> + *
>> + * Extracts the node ID and error ID from the netlink attributes and
>> + * retrieves the current value of the corresponding error counter. Sends the
>> + * result back to the requesting user via the standard Genl reply.
>> + *
>> + * Return: 0 on success, or negative errno on failure.
>> + */
>> +int drm_ras_nl_query_error_counter_doit(struct sk_buff *skb,
>> + struct genl_info *info)
>> +{
>> + u32 node_id, error_id;
>> +
>> + if (!info->attrs ||
>> + !info->attrs[DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID] ||
>> + !info->attrs[DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_ID])
>> + return -EINVAL;
>> +
>> + node_id = nla_get_u32(info->attrs[DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID]);
>> + error_id = nla_get_u32(info->attrs[DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_ID]);
>> +
>> + return doit_reply_value(info, node_id, error_id);
>> +}
>> +
>> +/**
>> + * drm_ras_node_register() - Register a new RAS node
>> + * @node: Node structure to register
>> + *
>> + * Adds the given RAS node to the global node xarray and assigns it
>> + * a unique ID. Both @node->name and @node->type must be valid.
>> + *
>> + * Return: 0 on success, or negative errno on failure:
>> + */
>> +int drm_ras_node_register(struct drm_ras_node *node)
>> +{
>> + if (!node->device_name || !node->node_name)
>> + return -EINVAL;
>> +
>> + /* Currently, only Error Counter Endpoinnts are supported */
>> + if (node->type != DRM_RAS_NODE_TYPE_ERROR_COUNTER)
>> + return -EINVAL;
>> +
>> + /* Mandatorty entries for Error Counter Node */
>> + if (node->type == DRM_RAS_NODE_TYPE_ERROR_COUNTER &&
>> + (!node->error_counter_range.last || !node->query_error_counter))
>> + return -EINVAL;
>> +
>> + return xa_alloc(&drm_ras_xa, &node->id, node, xa_limit_32b, GFP_KERNEL);
>> +}
>> +EXPORT_SYMBOL(drm_ras_node_register);
>> +
>> +/**
>> + * drm_ras_node_unregister() - Unregister a previously registered node
>> + * @node: Node structure to unregister
>> + *
>> + * Removes the given node from the global node xarray using its ID.
>> + */
>> +void drm_ras_node_unregister(struct drm_ras_node *node)
>> +{
>> + xa_erase(&drm_ras_xa, node->id);
>> +}
>> +EXPORT_SYMBOL(drm_ras_node_unregister);
>> diff --git a/drivers/gpu/drm/drm_ras_genl_family.c b/drivers/gpu/drm/drm_ras_genl_family.c
>> new file mode 100644
>> index 000000000000..2d818b8c3808
>> --- /dev/null
>> +++ b/drivers/gpu/drm/drm_ras_genl_family.c
>> @@ -0,0 +1,42 @@
>> +// SPDX-License-Identifier: MIT
>> +/*
>> + * Copyright © 2025 Intel Corporation
>> + */
>> +
>> +#include <drm/drm_ras_genl_family.h>
>> +#include <drm/drm_ras_nl.h>
>> +
>> +/* Track family registration so the drm_exit can be called at any time */
>> +static bool registered;
>> +
>> +/**
>> + * drm_ras_genl_family_register() - Register drm-ras genl family
>> + *
>> + * Only to be called one at drm_drv_init()
>> + */
>> +int drm_ras_genl_family_register(void)
>> +{
>> + int ret;
>> +
>> + registered = false;
>> +
>> + ret = genl_register_family(&drm_ras_nl_family);
>> + if (ret)
>> + return ret;
>> +
>> + registered = true;
>> + return 0;
>> +}
>> +
>> +/**
>> + * drm_ras_genl_family_unregister() - Unregister drm-ras genl family
>> + *
>> + * To be called one at drm_drv_exit() at any moment, but only once.
>> + */
>> +void drm_ras_genl_family_unregister(void)
>> +{
>> + if (registered) {
>> + genl_unregister_family(&drm_ras_nl_family);
>> + registered = false;
>> + }
>> +}
>> diff --git a/drivers/gpu/drm/drm_ras_nl.c b/drivers/gpu/drm/drm_ras_nl.c
>> new file mode 100644
>> index 000000000000..fcd1392410e4
>> --- /dev/null
>> +++ b/drivers/gpu/drm/drm_ras_nl.c
>> @@ -0,0 +1,54 @@
>> +// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
>> +/* Do not edit directly, auto-generated from: */
>> +/* Documentation/netlink/specs/drm_ras.yaml */
>> +/* YNL-GEN kernel source */
>> +
>> +#include <net/netlink.h>
>> +#include <net/genetlink.h>
>> +
>> +#include <uapi/drm/drm_ras.h>
>> +#include <drm/drm_ras_nl.h>
>> +
>> +/* DRM_RAS_CMD_GET_ERROR_COUNTERS - dump */
>> +static const struct nla_policy drm_ras_get_error_counters_nl_policy[DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID + 1] = {
>> + [DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID] = { .type = NLA_U32, },
>> +};
>> +
>> +/* DRM_RAS_CMD_QUERY_ERROR_COUNTER - do */
>> +static const struct nla_policy drm_ras_query_error_counter_nl_policy[DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_ID + 1] = {
>> + [DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID] = { .type = NLA_U32, },
>> + [DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_ID] = { .type = NLA_U32, },
>> +};
>> +
>> +/* Ops table for drm_ras */
>> +static const struct genl_split_ops drm_ras_nl_ops[] = {
>> + {
>> + .cmd = DRM_RAS_CMD_LIST_NODES,
>> + .dumpit = drm_ras_nl_list_nodes_dumpit,
>> + .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP,
>> + },
>> + {
>> + .cmd = DRM_RAS_CMD_GET_ERROR_COUNTERS,
>> + .dumpit = drm_ras_nl_get_error_counters_dumpit,
>> + .policy = drm_ras_get_error_counters_nl_policy,
>> + .maxattr = DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID,
>> + .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP,
>> + },
>> + {
>> + .cmd = DRM_RAS_CMD_QUERY_ERROR_COUNTER,
>> + .doit = drm_ras_nl_query_error_counter_doit,
>> + .policy = drm_ras_query_error_counter_nl_policy,
>> + .maxattr = DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_ID,
>> + .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
>> + },
>> +};
>> +
>> +struct genl_family drm_ras_nl_family __ro_after_init = {
>> + .name = DRM_RAS_FAMILY_NAME,
>> + .version = DRM_RAS_FAMILY_VERSION,
>> + .netnsok = true,
>> + .parallel_ops = true,
>> + .module = THIS_MODULE,
>> + .split_ops = drm_ras_nl_ops,
>> + .n_split_ops = ARRAY_SIZE(drm_ras_nl_ops),
>> +};
>> diff --git a/include/drm/drm_ras.h b/include/drm/drm_ras.h
>> new file mode 100644
>> index 000000000000..bba47a282ef8
>> --- /dev/null
>> +++ b/include/drm/drm_ras.h
>> @@ -0,0 +1,76 @@
>> +/* SPDX-License-Identifier: MIT */
>> +/*
>> + * Copyright © 2025 Intel Corporation
>> + */
>> +
>> +#ifndef __DRM_RAS_H__
>> +#define __DRM_RAS_H__
>> +
>> +#include "drm_ras_nl.h"
>> +
>> +/**
>> + * struct drm_ras_node - A DRM RAS Node
>> + */
>> +struct drm_ras_node {
>> + /** @id: Unique identifier for the node. Dynamically assigned. */
>> + u32 id;
>> + /**
>> + * @device_name: Human-readable name of the device. Given by the driver.
>> + */
>> + const char *device_name;
>> + /** @node_name: Human-readable name of the node. Given by the driver. */
>> + const char *node_name;
>> + /** @type: Type of the node (enum drm_ras_node_type). */
>> + enum drm_ras_node_type type;
>> +
>> + /* Error-Counter Related Callback and Variables */
>> +
>> + /** @error_counter_range: Range of valid Error IDs for this node. */
>> + struct {
>> + /** @first: First valid Error ID. */
>> + u32 first;
>> + /** @last: Last valid Error ID. Mandatory entry. */
>> + u32 last;
>> + } error_counter_range;
>> +
>> + /**
>> + * @query_error_counter:
>> + *
>> + * This callback is used by drm-ras to query a specific error counter.
>> + * counters supported by this node. Used for input check and to
>> + * iterate in all counters.
>> + *
>> + * Driver should expect query_error_counters() to be called with
>> + * error_id from `error_counter_range.first` to
>> + * `error_counter_range.last`.
>> + *
>> + * The @query_error_counter is a mandatory callback for
>> + * error_counter_node.
>> + *
>> + * Returns: 0 on success,
>> + * -ENOENT when error_id is not supported as an indication that
>> + * drm_ras should silently skip this entry. Used for
>> + * supporting non-contiguous error ranges.
>> + * Driver is responsible for maintaining the list of
>> + * supported error IDs in the range of first to last.
>> + * Other negative values on errors that should terminate the
>> + * netlink query.
>> + */
>> + int (*query_error_counter)(struct drm_ras_node *ep, u32 error_id,
>> + const char **name, u32 *val);
>> +
>> + /** @priv: Driver private data */
>> + void *priv;
>> +};
>> +
If new node types are frequently added, this struct may contain many
unused fields. It seems like the necessary members for any given node
type are: id, device_name, node_name, type, and priv. However, since
this functionality is designed specifically for RAS, I think its ok.
>> +struct drm_device;
>> +
>> +#if IS_ENABLED(CONFIG_DRM_RAS)
>> +int drm_ras_node_register(struct drm_ras_node *ep);
>> +void drm_ras_node_unregister(struct drm_ras_node *ep);
>> +#else
>> +static inline int drm_ras_node_register(struct drm_ras_node *ep) { return 0; }
>> +static inline void drm_ras_node_unregister(struct drm_ras_node *ep) { }
>> +#endif
>> +
>> +#endif
>> diff --git a/include/drm/drm_ras_genl_family.h b/include/drm/drm_ras_genl_family.h
>> new file mode 100644
>> index 000000000000..5931b53429f1
>> --- /dev/null
>> +++ b/include/drm/drm_ras_genl_family.h
>> @@ -0,0 +1,17 @@
>> +/* SPDX-License-Identifier: MIT */
>> +/*
>> + * Copyright © 2025 Intel Corporation
>> + */
>> +
>> +#ifndef __DRM_RAS_GENL_FAMILY_H__
>> +#define __DRM_RAS_GENL_FAMILY_H__
>> +
>> +#if IS_ENABLED(CONFIG_DRM_RAS)
>> +int drm_ras_genl_family_register(void);
>> +void drm_ras_genl_family_unregister(void);
>> +#else
>> +static inline int drm_ras_genl_family_register(void) { return 0; }
>> +static inline void drm_ras_genl_family_unregister(void) { }
>> +#endif
>> +
>> +#endif
>> diff --git a/include/drm/drm_ras_nl.h b/include/drm/drm_ras_nl.h
>> new file mode 100644
>> index 000000000000..9613b7d9ffdb
>> --- /dev/null
>> +++ b/include/drm/drm_ras_nl.h
>> @@ -0,0 +1,24 @@
>> +/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
>> +/* Do not edit directly, auto-generated from: */
>> +/* Documentation/netlink/specs/drm_ras.yaml */
>> +/* YNL-GEN kernel header */
>> +
>> +#ifndef _LINUX_DRM_RAS_GEN_H
>> +#define _LINUX_DRM_RAS_GEN_H
>> +
>> +#include <net/netlink.h>
>> +#include <net/genetlink.h>
>> +
>> +#include <uapi/drm/drm_ras.h>
>> +#include <drm/drm_ras_nl.h>
>> +
>> +int drm_ras_nl_list_nodes_dumpit(struct sk_buff *skb,
>> + struct netlink_callback *cb);
>> +int drm_ras_nl_get_error_counters_dumpit(struct sk_buff *skb,
>> + struct netlink_callback *cb);
>> +int drm_ras_nl_query_error_counter_doit(struct sk_buff *skb,
>> + struct genl_info *info);
>> +
>> +extern struct genl_family drm_ras_nl_family;
>> +
>> +#endif /* _LINUX_DRM_RAS_GEN_H */
>> diff --git a/include/uapi/drm/drm_ras.h b/include/uapi/drm/drm_ras.h
>> new file mode 100644
>> index 000000000000..3415ba345ac8
>> --- /dev/null
>> +++ b/include/uapi/drm/drm_ras.h
>> @@ -0,0 +1,49 @@
>> +/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
>> +/* Do not edit directly, auto-generated from: */
>> +/* Documentation/netlink/specs/drm_ras.yaml */
>> +/* YNL-GEN uapi header */
>> +
>> +#ifndef _UAPI_LINUX_DRM_RAS_H
>> +#define _UAPI_LINUX_DRM_RAS_H
>> +
>> +#define DRM_RAS_FAMILY_NAME "drm-ras"
>> +#define DRM_RAS_FAMILY_VERSION 1
>> +
>> +/*
>> + * Type of the node. Currently, only error-counter nodes are supported, which
>> + * expose reliability counters for a hardware/software component.
>> + */
>> +enum drm_ras_node_type {
>> + DRM_RAS_NODE_TYPE_ERROR_COUNTER = 1,
>> +};
>> +
>> +enum {
>> + DRM_RAS_A_NODE_ATTRS_NODE_ID = 1,
>> + DRM_RAS_A_NODE_ATTRS_DEVICE_NAME,
>> + DRM_RAS_A_NODE_ATTRS_NODE_NAME,
>> + DRM_RAS_A_NODE_ATTRS_NODE_TYPE,
>> +
>> + __DRM_RAS_A_NODE_ATTRS_MAX,
>> + DRM_RAS_A_NODE_ATTRS_MAX = (__DRM_RAS_A_NODE_ATTRS_MAX - 1)
>> +};
>> +
>> +enum {
>> + DRM_RAS_A_ERROR_COUNTER_ATTRS_NODE_ID = 1,
>> + DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_ID,
>> + DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_NAME,
>> + DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_VALUE,
>> +
>> + __DRM_RAS_A_ERROR_COUNTER_ATTRS_MAX,
>> + DRM_RAS_A_ERROR_COUNTER_ATTRS_MAX = (__DRM_RAS_A_ERROR_COUNTER_ATTRS_MAX - 1)
>> +};
>> +
>> +enum {
>> + DRM_RAS_CMD_LIST_NODES = 1,
>> + DRM_RAS_CMD_GET_ERROR_COUNTERS,
>> + DRM_RAS_CMD_QUERY_ERROR_COUNTER,
>> +
>> + __DRM_RAS_CMD_MAX,
>> + DRM_RAS_CMD_MAX = (__DRM_RAS_CMD_MAX - 1)
>> +};
>> +
>> +#endif /* _UAPI_LINUX_DRM_RAS_H */
>> --
>> 2.47.1
>>
Thanks,
Zack
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