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Date: Mon, 3 Feb 2014 18:13:52 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc: "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/5] cpu: add generic support for CPU feature based module autoloading
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@...aro.org> 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@...aro.org>
> ---
> 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@...aro.org>
> + *
> + * 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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