Re: [PATCH 2/5] cpu: add generic support for CPU feature based module autoloading

From: Ard Biesheuvel
Date: Mon Feb 03 2014 - 12:14:02 EST

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Hello Greg,

Would you care to comment on this patch?

It adds some Kconfig clutter, but this is removed again in the next patch
(http://marc.info/?l=linux-arm-kernel&m=139101443708663&w=2),
which has already been acked by hpa here:
http://marc.info/?l=linux-arm-kernel&m=139101589509168&w=2

Example enabling it for arm64:
http://marc.info/?l=linux-arm-kernel&m=139101486308822&w=2

Example using it (optional AES instructions on arm64):
http://marc.info/?l=linux-arm-kernel&m=139101446008665&w=2

Best regards,
Ard.

On 29 January 2014 17:50, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> This patch adds support for advertising optional CPU features over udev using
> the modalias, and for declaring compatibility with/dependency upon such a
> feature in a module.
>
> This feature can be enabled by setting CONFIG_GENERIC_CPU_AUTOPROBE for the
> architecture, and supplying a file <asm/cpufeature.h> which defines how the
> numbers used in the modalias string map to actual CPU features.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> drivers/base/Kconfig | 8 ++++++
> drivers/base/cpu.c | 39 +++++++++++++++++++++----
> include/linux/cpufeature.h | 60 +++++++++++++++++++++++++++++++++++++++
> include/linux/mod_devicetable.h | 9 ++++++
> scripts/mod/devicetable-offsets.c | 3 ++
> scripts/mod/file2alias.c | 10 +++++++
> 6 files changed, 123 insertions(+), 6 deletions(-)
> create mode 100644 include/linux/cpufeature.h
>
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index ec36e7772e57..3f0d3732df7f 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -185,6 +185,14 @@ config GENERIC_CPU_DEVICES
> bool
> default n
>
> +config HAVE_CPU_AUTOPROBE
> + def_bool ARCH_HAS_CPU_AUTOPROBE
> +
> +config GENERIC_CPU_AUTOPROBE
> + bool
> + depends on !ARCH_HAS_CPU_AUTOPROBE
> + select HAVE_CPU_AUTOPROBE
> +
> config SOC_BUS
> bool
>
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 270649012e64..8a38bf8c792f 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -15,6 +15,7 @@
> #include <linux/percpu.h>
> #include <linux/acpi.h>
> #include <linux/of.h>
> +#include <linux/cpufeature.h>
>
> #include "base.h"
>
> @@ -286,12 +287,38 @@ static void cpu_device_release(struct device *dev)
> */
> }
>
> -#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
> +#ifdef CONFIG_HAVE_CPU_AUTOPROBE
> +#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
> +static ssize_t print_cpu_modalias(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + ssize_t n;
> + u32 i;
> +
> + n = sprintf(buf, "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
> + CPU_FEATURE_TYPEVAL);
> +
> + for (i = 0; i < MAX_CPU_FEATURES; i++)
> + if (cpu_have_feature(i)) {
> + if (PAGE_SIZE < n + sizeof(",XXXX\n")) {
> + WARN(1, "CPU features overflow page\n");
> + break;
> + }
> + n += sprintf(&buf[n], ",%04X", i);
> + }
> + buf[n++] = '\n';
> + return n;
> +}
> +#else
> +#define print_cpu_modalias arch_print_cpu_modalias
> +#endif
> +
> static int cpu_uevent(struct device *dev, struct kobj_uevent_env *env)
> {
> char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> if (buf) {
> - arch_print_cpu_modalias(NULL, NULL, buf);
> + print_cpu_modalias(NULL, NULL, buf);
> add_uevent_var(env, "MODALIAS=%s", buf);
> kfree(buf);
> }
> @@ -319,7 +346,7 @@ int register_cpu(struct cpu *cpu, int num)
> cpu->dev.offline_disabled = !cpu->hotpluggable;
> cpu->dev.offline = !cpu_online(num);
> cpu->dev.of_node = of_get_cpu_node(num, NULL);
> -#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
> +#ifdef CONFIG_HAVE_CPU_AUTOPROBE
> cpu->dev.bus->uevent = cpu_uevent;
> #endif
> cpu->dev.groups = common_cpu_attr_groups;
> @@ -343,8 +370,8 @@ struct device *get_cpu_device(unsigned cpu)
> }
> EXPORT_SYMBOL_GPL(get_cpu_device);
>
> -#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
> -static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
> +#ifdef CONFIG_HAVE_CPU_AUTOPROBE
> +static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
> #endif
>
> static struct attribute *cpu_root_attrs[] = {
> @@ -357,7 +384,7 @@ static struct attribute *cpu_root_attrs[] = {
> &cpu_attrs[2].attr.attr,
> &dev_attr_kernel_max.attr,
> &dev_attr_offline.attr,
> -#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
> +#ifdef CONFIG_HAVE_CPU_AUTOPROBE
> &dev_attr_modalias.attr,
> #endif
> NULL
> diff --git a/include/linux/cpufeature.h b/include/linux/cpufeature.h
> new file mode 100644
> index 000000000000..c4d4eb8ac9fe
> --- /dev/null
> +++ b/include/linux/cpufeature.h
> @@ -0,0 +1,60 @@
> +/*
> + * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@xxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef __LINUX_CPUFEATURE_H
> +#define __LINUX_CPUFEATURE_H
> +
> +#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
> +
> +#include <linux/mod_devicetable.h>
> +#include <asm/cpufeature.h>
> +
> +/*
> + * Macros imported from <asm/cpufeature.h>:
> + * - cpu_feature(x) ordinal value of feature called 'x'
> + * - cpu_have_feature(u32 n) whether feature #n is available
> + * - MAX_CPU_FEATURES upper bound for feature ordinal values
> + * Optional:
> + * - CPU_FEATURE_TYPEFMT format string fragment for printing the cpu type
> + * - CPU_FEATURE_TYPEVAL set of values matching the format string above
> + */
> +
> +#ifndef CPU_FEATURE_TYPEFMT
> +#define CPU_FEATURE_TYPEFMT "%s"
> +#endif
> +
> +#ifndef CPU_FEATURE_TYPEVAL
> +#define CPU_FEATURE_TYPEVAL ELF_PLATFORM
> +#endif
> +
> +/*
> + * Use module_cpu_feature_match(feature, module_init_function) to
> + * declare that
> + * a) the module shall be probed upon discovery of CPU feature 'feature'
> + * (typically at boot time using udev)
> + * b) the module must not be loaded if CPU feature 'feature' is not present
> + * (not even by manual insmod).
> + *
> + * For a list of legal values for 'feature', please consult the file
> + * 'asm/cpufeature.h' of your favorite architecture.
> + */
> +#define module_cpu_feature_match(x, __init) \
> +static struct cpu_feature const cpu_feature_match_ ## x[] = \
> + { { .feature = cpu_feature(x) }, { } }; \
> +MODULE_DEVICE_TABLE(cpu, cpu_feature_match_ ## x); \
> + \
> +static int cpu_feature_match_ ## x ## _init(void) \
> +{ \
> + if (!cpu_have_feature(cpu_feature(x))) \
> + return -ENODEV; \
> + return __init(); \
> +} \
> +module_init(cpu_feature_match_ ## x ## _init)
> +
> +#endif
> +#endif
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index 45e921401b06..f2ac87c613a5 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -564,6 +564,15 @@ struct x86_cpu_id {
> #define X86_MODEL_ANY 0
> #define X86_FEATURE_ANY 0 /* Same as FPU, you can't test for that */
>
> +/*
> + * Generic table type for matching CPU features.
> + * @feature: the bit number of the feature (0 - 65535)
> + */
> +
> +struct cpu_feature {
> + __u16 feature;
> +};
> +
> #define IPACK_ANY_FORMAT 0xff
> #define IPACK_ANY_ID (~0)
> struct ipack_device_id {
> diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
> index bb5d115ca671..f282516acc7b 100644
> --- a/scripts/mod/devicetable-offsets.c
> +++ b/scripts/mod/devicetable-offsets.c
> @@ -174,6 +174,9 @@ int main(void)
> DEVID_FIELD(x86_cpu_id, model);
> DEVID_FIELD(x86_cpu_id, vendor);
>
> + DEVID(cpu_feature);
> + DEVID_FIELD(cpu_feature, feature);
> +
> DEVID(mei_cl_device_id);
> DEVID_FIELD(mei_cl_device_id, name);
>
> diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> index 23708636b05c..8a69005228d8 100644
> --- a/scripts/mod/file2alias.c
> +++ b/scripts/mod/file2alias.c
> @@ -1135,6 +1135,16 @@ static int do_x86cpu_entry(const char *filename, void *symval,
> }
> ADD_TO_DEVTABLE("x86cpu", x86_cpu_id, do_x86cpu_entry);
>
> +/* LOOKS like cpu:type:*:feature:*FEAT* */
> +static int do_cpu_entry(const char *filename, void *symval, char *alias)
> +{
> + DEF_FIELD(symval, cpu_feature, feature);
> +
> + sprintf(alias, "cpu:type:*:feature:*%04X*", feature);
> + return 1;
> +}
> +ADD_TO_DEVTABLE("cpu", cpu_feature, do_cpu_entry);
> +
> /* Looks like: mei:S */
> static int do_mei_entry(const char *filename, void *symval,
> char *alias)
> --
> 1.8.3.2
>
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Next message: Alex Thorlton: "Re: [PATCH 1/3] Revert "thp: make MADV_HUGEPAGE check formm->def_flags""
Previous message: boris brezillon: "Re: [PATCH] at91: pmc: Fixed irq's name allocation for programmableclocks"
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