Re: [PATCH v2 09/10] PM: EM: Implement em_notify_pd_created/updated().

Re: [PATCH v2 09/10] PM: EM: Implement em_notify_pd_created/updated().

[kernel test robot]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20250613094428.267791-10-changwoo@igalia.com>
References: <20250613094428.267791-10-changwoo@igalia.com>
TO: Changwoo Min <changwoo@igalia.com>
TO: lukasz.luba@arm.com
TO: rafael@kernel.org
TO: len.brown@intel.com
TO: pavel@kernel.org
CC: christian.loehle@arm.com
CC: tj@kernel.org
CC: kernel-dev@igalia.com
CC: linux-pm@vger.kernel.org
CC: sched-ext@lists.linux.dev
CC: linux-kernel@vger.kernel.org
CC: Changwoo Min <changwoo@igalia.com>

Hi Changwoo,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.16-rc2 next-20250618]
[cannot apply to amd-pstate/linux-next amd-pstate/bleeding-edge]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Changwoo-Min/PM-EM-Add-em-yaml-and-autogen-files/20250613-174859
base:   linus/master
patch link:    https://lore.kernel.org/r/20250613094428.267791-10-changwoo%40igalia.com
patch subject: [PATCH v2 09/10] PM: EM: Implement em_notify_pd_created/updated().
:::::: branch date: 5 days ago
:::::: commit date: 5 days ago
config: x86_64-randconfig-161-20250618 (https://download.01.org/0day-ci/archive/20250618/202506181708.P4eRyPUC-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202506181708.P4eRyPUC-lkp@intel.com/

smatch warnings:
kernel/power/em_netlink.c:249 __em_notify_pd_table() error: uninitialized symbol 'ret'.

vim +/ret +249 kernel/power/em_netlink.c

24b309699bc739 Changwoo Min 2025-06-13  215  
b0668476cf48ef Changwoo Min 2025-06-13  216  
b0668476cf48ef Changwoo Min 2025-06-13  217  /**************************** Event encoding *********************************/
76ab710f256a78 Changwoo Min 2025-06-13  218  static int __em_notify_pd_table(const struct em_perf_domain *pd, int ntf_type)
76ab710f256a78 Changwoo Min 2025-06-13  219  {
76ab710f256a78 Changwoo Min 2025-06-13  220  	struct sk_buff *msg;
76ab710f256a78 Changwoo Min 2025-06-13  221  	int msg_sz, ret;
76ab710f256a78 Changwoo Min 2025-06-13  222  	void *hdr;
76ab710f256a78 Changwoo Min 2025-06-13  223  
76ab710f256a78 Changwoo Min 2025-06-13  224  	if (!genl_has_listeners(&em_nl_family, &init_net, EM_NLGRP_EVENT))
76ab710f256a78 Changwoo Min 2025-06-13  225  		return 0;
76ab710f256a78 Changwoo Min 2025-06-13  226  
76ab710f256a78 Changwoo Min 2025-06-13  227  	msg_sz = __em_nl_get_pd_table_size(pd);
76ab710f256a78 Changwoo Min 2025-06-13  228  
76ab710f256a78 Changwoo Min 2025-06-13  229  	msg = genlmsg_new(msg_sz, GFP_KERNEL);
76ab710f256a78 Changwoo Min 2025-06-13  230  	if (!msg)
76ab710f256a78 Changwoo Min 2025-06-13  231  		return -ENOMEM;
76ab710f256a78 Changwoo Min 2025-06-13  232  
76ab710f256a78 Changwoo Min 2025-06-13  233  	hdr = genlmsg_put(msg, 0, 0, &em_nl_family, 0, ntf_type);
76ab710f256a78 Changwoo Min 2025-06-13  234  	if (!hdr)
76ab710f256a78 Changwoo Min 2025-06-13  235  		goto out_free_msg;
76ab710f256a78 Changwoo Min 2025-06-13  236  
76ab710f256a78 Changwoo Min 2025-06-13  237  	ret = __em_nl_get_pd_table(msg, pd);
76ab710f256a78 Changwoo Min 2025-06-13  238  	if (ret)
76ab710f256a78 Changwoo Min 2025-06-13  239  		goto out_free_msg;
76ab710f256a78 Changwoo Min 2025-06-13  240  
76ab710f256a78 Changwoo Min 2025-06-13  241  	genlmsg_end(msg, hdr);
76ab710f256a78 Changwoo Min 2025-06-13  242  
76ab710f256a78 Changwoo Min 2025-06-13  243  	genlmsg_multicast(&em_nl_family, msg, 0, EM_NLGRP_EVENT, GFP_KERNEL);
76ab710f256a78 Changwoo Min 2025-06-13  244  
76ab710f256a78 Changwoo Min 2025-06-13  245  	return 0;
76ab710f256a78 Changwoo Min 2025-06-13  246  
76ab710f256a78 Changwoo Min 2025-06-13  247  out_free_msg:
76ab710f256a78 Changwoo Min 2025-06-13  248  	nlmsg_free(msg);
76ab710f256a78 Changwoo Min 2025-06-13 @249  	return ret;
76ab710f256a78 Changwoo Min 2025-06-13  250  }
76ab710f256a78 Changwoo Min 2025-06-13  251  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[PATCH v2 00/10] PM: EM: Add netlink support for the energy model.

[Changwoo Min]

There is a need to access the energy model from the userspace. One such
example is the sched_ext schedulers [1]. The userspace part of the
sched_ext schedules could feed the (post-processed) energy-model
information to the BPF part of the scheduler.

Currently, debugfs is the only way to read the energy model from userspace;
however, it lacks proper notification mechanisms when a performance domain
and its associated energy model change.

This patch set introduces a generic netlink for the energy model, as
discussed in [2]. It allows a userspace program to read the performance
domain and its energy model. It notifies the userspace program when a
performance domain is created or deleted or its energy model is updated
through a multicast interface.

Specifically, it supports two commands:
  - EM_CMD_GET_PDS: Get the list of information for all performance
    domains.
  - EM_CMD_GET_PD_TABLE: Get the energy model table of a performance
    domain.

Also, it supports three notification events:
  - EM_CMD_PD_CREATED: When a performance domain is created.
  - EM_CMD_PD_DELETED: When a performance domain is deleted.
  - EM_CMD_PD_UPDATED: When the energy model table of a performance domain
    is updated.

This can be tested using the tool, tools/net/ynl/pyynl/cli.py, for example,
with the following commands:

  $> tools/net/ynl/pyynl/cli.py \
     --spec Documentation/netlink/specs/em.yaml \
     --do get-pds
  $> tools/net/ynl/pyynl/cli.py \
     --spec Documentation/netlink/specs/em.yaml \
     --do get-pd-table --json '{"pd-id": 0}'
  $> tools/net/ynl/pyynl/cli.py \
     --spec Documentation/netlink/specs/em.yaml \
     --subscribe event  --sleep 10

[1] https://lwn.net/Articles/922405/
[2] https://lore.kernel.org/lkml/a82423bc-8c38-4d57-93da-c4f20011cc92@arm.com/

ChangeLog v1 -> v2:
  - Use YNL to generate boilerplate code. Overhaul the naming conventions
    (command, event, notification, attribute) to follow the typical
    conventions of other YNL-based netlink implementations.
  - Calculate the exact message size instead of using NLMSG_GOODSIZE
    when allocating a message (genlmsg_new). This avoids the reallocation
    of a message.
  - Remove an unnecessary function, em_netlink_exit(), and initialize the
    netlink (em_netlink_init) at em_netlink.c without touching energy_model.c.

CC: Lukasz Luba <lukasz.luba@arm.com>
CC: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CC: Tejun Heo <tj@kernel.org>
Signed-off-by: Changwoo Min <changwoo@igalia.com>

Changwoo Min (10):
  PM: EM: Add em.yaml and autogen files.
  PM: EM: Add a skeleton code for netlink notification.
  PM: EM: Assign a unique ID when creating a performance domain.
  PM: EM: Expose the ID of a performance domain via debugfs.
  PM: EM: Add an iterator and accessor for the performance domain.
  PM: EM: Implement em_nl_get_pds_doit().
  PM: EM: Implement em_nl_get_pd_table_doit().
  PM: EM: Implement em_notify_pd_deleted().
  PM: EM: Implement em_notify_pd_created/updated().
  PM: EM: Notify an event when the performance domain changes.

 Documentation/netlink/specs/em.yaml | 113 ++++++++++
 MAINTAINERS                         |   3 +
 include/linux/energy_model.h        |  19 ++
 include/uapi/linux/energy_model.h   |  62 ++++++
 kernel/power/Makefile               |   5 +-
 kernel/power/em_netlink.c           | 311 ++++++++++++++++++++++++++++
 kernel/power/em_netlink.h           |  34 +++
 kernel/power/em_netlink_autogen.c   |  48 +++++
 kernel/power/em_netlink_autogen.h   |  23 ++
 kernel/power/energy_model.c         |  83 +++++++-
 10 files changed, 699 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/netlink/specs/em.yaml
 create mode 100644 include/uapi/linux/energy_model.h
 create mode 100644 kernel/power/em_netlink.c
 create mode 100644 kernel/power/em_netlink.h
 create mode 100644 kernel/power/em_netlink_autogen.c
 create mode 100644 kernel/power/em_netlink_autogen.h

-- 
2.49.0

[PATCH v2 09/10] PM: EM: Implement em_notify_pd_created/updated().

[Changwoo Min]

Implement two event notifications when a performance domain is created
(EM_CMD_PD_CREATED) and updated (EM_CMD_PD_UPDATED). The message format
of these two event notifications is the same as EM_CMD_GET_PD_TABLE --
containing the performance domain's ID and its energy model table.

Signed-off-by: Changwoo Min <changwoo@igalia.com>
---
 kernel/power/em_netlink.c | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/kernel/power/em_netlink.c b/kernel/power/em_netlink.c
index 4e34799fd1f8..d42da92d1af4 100644
--- a/kernel/power/em_netlink.c
+++ b/kernel/power/em_netlink.c
@@ -215,14 +215,48 @@ int em_nl_get_pd_table_doit(struct sk_buff *skb, struct genl_info *info)
 
 
 /**************************** Event encoding *********************************/
+static int __em_notify_pd_table(const struct em_perf_domain *pd, int ntf_type)
+{
+	struct sk_buff *msg;
+	int msg_sz, ret;
+	void *hdr;
+
+	if (!genl_has_listeners(&em_nl_family, &init_net, EM_NLGRP_EVENT))
+		return 0;
+
+	msg_sz = __em_nl_get_pd_table_size(pd);
+
+	msg = genlmsg_new(msg_sz, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_put(msg, 0, 0, &em_nl_family, 0, ntf_type);
+	if (!hdr)
+		goto out_free_msg;
+
+	ret = __em_nl_get_pd_table(msg, pd);
+	if (ret)
+		goto out_free_msg;
+
+	genlmsg_end(msg, hdr);
+
+	genlmsg_multicast(&em_nl_family, msg, 0, EM_NLGRP_EVENT, GFP_KERNEL);
+
+	return 0;
+
+out_free_msg:
+	nlmsg_free(msg);
+	return ret;
+}
+
 int em_notify_pd_created(const struct em_perf_domain *pd)
 {
-	return -EOPNOTSUPP;
+	return __em_notify_pd_table(pd, EM_CMD_PD_CREATED);
 }
 
 int em_notify_pd_updated(const struct em_perf_domain *pd)
 {
-	return -EOPNOTSUPP;
+	return __em_notify_pd_table(pd, EM_CMD_PD_UPDATED);
 }
 
 static int __em_notify_pd_deleted_size(const struct em_perf_domain *pd)
-- 
2.49.0

Re: [PATCH v2 09/10] PM: EM: Implement em_notify_pd_created/updated().

[kernel test robot]

Hi Changwoo,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.16-rc1 next-20250613]
[cannot apply to amd-pstate/linux-next amd-pstate/bleeding-edge]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Changwoo-Min/PM-EM-Add-em-yaml-and-autogen-files/20250613-174859
base:   linus/master
patch link:    https://lore.kernel.org/r/20250613094428.267791-10-changwoo%40igalia.com
patch subject: [PATCH v2 09/10] PM: EM: Implement em_notify_pd_created/updated().
config: i386-randconfig-001-20250614 (https://download.01.org/0day-ci/archive/20250614/202506140306.tuIoz8rN-lkp@intel.com/config)
compiler: clang version 20.1.2 (https://github.com/llvm/llvm-project 58df0ef89dd64126512e4ee27b4ac3fd8ddf6247)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250614/202506140306.tuIoz8rN-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202506140306.tuIoz8rN-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/power/em_netlink.c:234:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
     234 |         if (!hdr)
         |             ^~~~
   kernel/power/em_netlink.c:249:9: note: uninitialized use occurs here
     249 |         return ret;
         |                ^~~
   kernel/power/em_netlink.c:234:2: note: remove the 'if' if its condition is always false
     234 |         if (!hdr)
         |         ^~~~~~~~~
     235 |                 goto out_free_msg;
         |                 ~~~~~~~~~~~~~~~~~
   kernel/power/em_netlink.c:221:17: note: initialize the variable 'ret' to silence this warning
     221 |         int msg_sz, ret;
         |                        ^
         |                         = 0
   1 warning generated.


vim +234 kernel/power/em_netlink.c

   215	
   216	
   217	/**************************** Event encoding *********************************/
   218	static int __em_notify_pd_table(const struct em_perf_domain *pd, int ntf_type)
   219	{
   220		struct sk_buff *msg;
   221		int msg_sz, ret;
   222		void *hdr;
   223	
   224		if (!genl_has_listeners(&em_nl_family, &init_net, EM_NLGRP_EVENT))
   225			return 0;
   226	
   227		msg_sz = __em_nl_get_pd_table_size(pd);
   228	
   229		msg = genlmsg_new(msg_sz, GFP_KERNEL);
   230		if (!msg)
   231			return -ENOMEM;
   232	
   233		hdr = genlmsg_put(msg, 0, 0, &em_nl_family, 0, ntf_type);
 > 234		if (!hdr)
   235			goto out_free_msg;
   236	
   237		ret = __em_nl_get_pd_table(msg, pd);
   238		if (ret)
   239			goto out_free_msg;
   240	
   241		genlmsg_end(msg, hdr);
   242	
   243		genlmsg_multicast(&em_nl_family, msg, 0, EM_NLGRP_EVENT, GFP_KERNEL);
   244	
   245		return 0;
   246	
   247	out_free_msg:
   248		nlmsg_free(msg);
   249		return ret;
   250	}
   251	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki