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[PATCH v2] MIPS: Expose prid and globalnumber to sysfs

Jiaxun Yang posted 1 patch 3 years, 8 months ago
There is a newer version of this series
.../ABI/testing/sysfs-devices-system-cpu      | 11 +++
arch/mips/kernel/topology.c                   | 96 +++++++++++++++++++
2 files changed, 107 insertions(+)
[PATCH v2] MIPS: Expose prid and globalnumber to sysfs
Posted by Jiaxun Yang 3 years, 8 months ago 
Some application would like to know precise model and rev of processor
to do errata workaround or optimization.

Expose them in sysfs as:
/sys/devices/system/cpu/cpuX/regs/identification/prid
/sys/devices/system/cpu/cpuX/regs/identification/globalnumber

Reusing AArch64 CPU registers directory.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
v2: Drop static qualifier for kobj (gregkh)
---
 .../ABI/testing/sysfs-devices-system-cpu      | 11 +++
 arch/mips/kernel/topology.c                   | 96 +++++++++++++++++++
 2 files changed, 107 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 5bf61881f012..adf855e7bb9b 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -512,6 +512,17 @@ Description:	information about CPUs heterogeneity.
 
 		cpu_capacity: capacity of cpuX.
 
+What:		/sys/devices/system/cpu/cpuX/regs/
+		/sys/devices/system/cpu/cpuX/regs/identification/
+		/sys/devices/system/cpu/cpuX/regs/identification/prid
+		/sys/devices/system/cpu/cpuX/regs/identification/globalnumber
+Date:		Augest 2022
+Contact:	Linux MIPS Kernel Mailing list <linux-mips@vger.kernel.org>
+Description:	MIPS CPU registers
+
+		'identification' directory exposes the Processor ID and Global Number
+		registers for identifying model and revision of the CPU.
+
 What:		/sys/devices/system/cpu/vulnerabilities
 		/sys/devices/system/cpu/vulnerabilities/meltdown
 		/sys/devices/system/cpu/vulnerabilities/spectre_v1
diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
index 9429d85a4703..0e3730f3c00f 100644
--- a/arch/mips/kernel/topology.c
+++ b/arch/mips/kernel/topology.c
@@ -5,6 +5,8 @@
 #include <linux/node.h>
 #include <linux/nodemask.h>
 #include <linux/percpu.h>
+#include <linux/seq_file.h>
+#include <linux/smp.h>
 
 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 
@@ -26,3 +28,97 @@ static int __init topology_init(void)
 }
 
 subsys_initcall(topology_init);
+
+static struct kobj_type cpuregs_kobj_type = {
+	.sysfs_ops = &kobj_sysfs_ops,
+};
+
+struct cpureg {
+	struct kobject kobj;
+	struct cpuinfo_mips *info;
+};
+DEFINE_PER_CPU(struct cpureg, cpuregs);
+
+#define kobj_to_cpureg(kobj)	container_of(kobj, struct cpureg, kobj)
+#define CPUREGS_ATTR_RO(_name, _field)						\
+	static ssize_t _name##_show(struct kobject *kobj,			\
+			struct kobj_attribute *attr, char *buf)			\
+	{									\
+		struct cpuinfo_mips *info = kobj_to_cpureg(kobj)->info;		\
+										\
+		return sprintf(buf, "0x%08x\n", info->_field);	\
+	}									\
+	static struct kobj_attribute cpuregs_attr_##_name = __ATTR_RO(_name)
+
+CPUREGS_ATTR_RO(prid, processor_id);
+CPUREGS_ATTR_RO(globalnumber, globalnumber);
+
+static struct attribute *cpuregs_id_attrs[] = {
+	&cpuregs_attr_prid.attr,
+	&cpuregs_attr_globalnumber.attr,
+	NULL
+};
+
+static const struct attribute_group cpuregs_attr_group = {
+	.attrs = cpuregs_id_attrs,
+	.name = "identification"
+};
+
+static int cpuregs_cpu_online(unsigned int cpu)
+{
+	int rc;
+	struct device *dev;
+	struct cpureg *reg = &per_cpu(cpuregs, cpu);
+
+	dev = get_cpu_device(cpu);
+	if (!dev) {
+		rc = -ENODEV;
+		goto out;
+	}
+	rc = kobject_add(&reg->kobj, &dev->kobj, "regs");
+	if (rc)
+		goto out;
+	rc = sysfs_create_group(&reg->kobj, &cpuregs_attr_group);
+	if (rc)
+		kobject_del(&reg->kobj);
+out:
+	return rc;
+}
+
+static int cpuregs_cpu_offline(unsigned int cpu)
+{
+	struct device *dev;
+	struct cpureg *reg = &per_cpu(cpuregs, cpu);
+
+	dev = get_cpu_device(cpu);
+	if (!dev)
+		return -ENODEV;
+	if (reg->kobj.parent) {
+		sysfs_remove_group(&reg->kobj, &cpuregs_attr_group);
+		kobject_del(&reg->kobj);
+	}
+
+	return 0;
+}
+
+static int __init cpuinfo_regs_init(void)
+{
+	int cpu, ret;
+
+	for_each_possible_cpu(cpu) {
+		struct cpureg *reg = &per_cpu(cpuregs, cpu);
+
+		reg->info = &cpu_data[cpu];
+		kobject_init(&reg->kobj, &cpuregs_kobj_type);
+	}
+
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mips/topology:online",
+				cpuregs_cpu_online, cpuregs_cpu_offline);
+	if (ret < 0) {
+		pr_err("cpuinfo: failed to register hotplug callbacks.\n");
+		return ret;
+	}
+	return 0;
+}
+
+device_initcall(cpuinfo_regs_init);
-- 
2.34.1
Re: [PATCH v2] MIPS: Expose prid and globalnumber to sysfs
Posted by Florian Fainelli 3 years, 8 months ago 

On 8/11/2022 3:12 AM, Jiaxun Yang wrote:
> Some application would like to know precise model and rev of processor
> to do errata workaround or optimization.
> 
> Expose them in sysfs as:
> /sys/devices/system/cpu/cpuX/regs/identification/prid
> /sys/devices/system/cpu/cpuX/regs/identification/globalnumber
> 
> Reusing AArch64 CPU registers directory.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
> v2: Drop static qualifier for kobj (gregkh)
> ---
>   .../ABI/testing/sysfs-devices-system-cpu      | 11 +++
>   arch/mips/kernel/topology.c                   | 96 +++++++++++++++++++
>   2 files changed, 107 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
> index 5bf61881f012..adf855e7bb9b 100644
> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
> @@ -512,6 +512,17 @@ Description:	information about CPUs heterogeneity.
>   
>   		cpu_capacity: capacity of cpuX.
>   
> +What:		/sys/devices/system/cpu/cpuX/regs/
> +		/sys/devices/system/cpu/cpuX/regs/identification/
> +		/sys/devices/system/cpu/cpuX/regs/identification/prid
> +		/sys/devices/system/cpu/cpuX/regs/identification/globalnumber
> +Date:		Augest 2022

typo: August

> +Contact:	Linux MIPS Kernel Mailing list <linux-mips@vger.kernel.org>
> +Description:	MIPS CPU registers
> +
> +		'identification' directory exposes the Processor ID and Global Number
> +		registers for identifying model and revision of the CPU.
> +
>   What:		/sys/devices/system/cpu/vulnerabilities
>   		/sys/devices/system/cpu/vulnerabilities/meltdown
>   		/sys/devices/system/cpu/vulnerabilities/spectre_v1
> diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
> index 9429d85a4703..0e3730f3c00f 100644
> --- a/arch/mips/kernel/topology.c
> +++ b/arch/mips/kernel/topology.c
> @@ -5,6 +5,8 @@
>   #include <linux/node.h>
>   #include <linux/nodemask.h>
>   #include <linux/percpu.h>
> +#include <linux/seq_file.h>
> +#include <linux/smp.h>
>   
>   static DEFINE_PER_CPU(struct cpu, cpu_devices);
>   
> @@ -26,3 +28,97 @@ static int __init topology_init(void)
>   }
>   
>   subsys_initcall(topology_init);
> +
> +static struct kobj_type cpuregs_kobj_type = {
> +	.sysfs_ops = &kobj_sysfs_ops,
> +};
> +
> +struct cpureg {
> +	struct kobject kobj;
> +	struct cpuinfo_mips *info;
> +};
> +DEFINE_PER_CPU(struct cpureg, cpuregs);
> +
> +#define kobj_to_cpureg(kobj)	container_of(kobj, struct cpureg, kobj)
> +#define CPUREGS_ATTR_RO(_name, _field)						\
> +	static ssize_t _name##_show(struct kobject *kobj,			\
> +			struct kobj_attribute *attr, char *buf)			\
> +	{									\
> +		struct cpuinfo_mips *info = kobj_to_cpureg(kobj)->info;		\
> +										\
> +		return sprintf(buf, "0x%08x\n", info->_field);	\

Would not you be able to simplify this greatly with just:

	struct cpuinfo_mips *info = current_cpu_data;

and not have to associate that with struct with the kobject?
-- 
Florian
Re: [PATCH v2] MIPS: Expose prid and globalnumber to sysfs
Posted by Greg KH 3 years, 8 months ago 
On Thu, Aug 11, 2022 at 10:12:36AM +0000, Jiaxun Yang wrote:
> Some application would like to know precise model and rev of processor
> to do errata workaround or optimization.
> 
> Expose them in sysfs as:
> /sys/devices/system/cpu/cpuX/regs/identification/prid
> /sys/devices/system/cpu/cpuX/regs/identification/globalnumber
> 
> Reusing AArch64 CPU registers directory.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
> v2: Drop static qualifier for kobj (gregkh)
> ---
>  .../ABI/testing/sysfs-devices-system-cpu      | 11 +++
>  arch/mips/kernel/topology.c                   | 96 +++++++++++++++++++
>  2 files changed, 107 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
> index 5bf61881f012..adf855e7bb9b 100644
> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
> @@ -512,6 +512,17 @@ Description:	information about CPUs heterogeneity.
>  
>  		cpu_capacity: capacity of cpuX.
>  
> +What:		/sys/devices/system/cpu/cpuX/regs/
> +		/sys/devices/system/cpu/cpuX/regs/identification/
> +		/sys/devices/system/cpu/cpuX/regs/identification/prid
> +		/sys/devices/system/cpu/cpuX/regs/identification/globalnumber
> +Date:		Augest 2022
> +Contact:	Linux MIPS Kernel Mailing list <linux-mips@vger.kernel.org>
> +Description:	MIPS CPU registers
> +
> +		'identification' directory exposes the Processor ID and Global Number
> +		registers for identifying model and revision of the CPU.

You do not document that this is only for MIPS processors.

Actually, why not do this for all chip types?  Why is this only for MIPS
chips?

> +
>  What:		/sys/devices/system/cpu/vulnerabilities
>  		/sys/devices/system/cpu/vulnerabilities/meltdown
>  		/sys/devices/system/cpu/vulnerabilities/spectre_v1
> diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
> index 9429d85a4703..0e3730f3c00f 100644
> --- a/arch/mips/kernel/topology.c
> +++ b/arch/mips/kernel/topology.c
> @@ -5,6 +5,8 @@
>  #include <linux/node.h>
>  #include <linux/nodemask.h>
>  #include <linux/percpu.h>
> +#include <linux/seq_file.h>
> +#include <linux/smp.h>
>  
>  static DEFINE_PER_CPU(struct cpu, cpu_devices);
>  
> @@ -26,3 +28,97 @@ static int __init topology_init(void)
>  }
>  
>  subsys_initcall(topology_init);
> +
> +static struct kobj_type cpuregs_kobj_type = {
> +	.sysfs_ops = &kobj_sysfs_ops,
> +};
> +
> +struct cpureg {
> +	struct kobject kobj;
> +	struct cpuinfo_mips *info;
> +};
> +DEFINE_PER_CPU(struct cpureg, cpuregs);

You still have static kobjects here, nothing changed from your previous
submission :(

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