[1/5] ARM: wire up HWCAP2 feature bits to the CPU modalias

Message ID 1476787939-21889-2-git-send-email-ard.biesheuvel@linaro.org
State New
Headers show

Commit Message

Ard Biesheuvel Oct. 18, 2016, 10:52 a.m.
Wire up the generic support for exposing CPU feature bits via the
modalias in /sys/device/system/cpu. This allows udev to automatically
load modules for things like crypto algorithms that are implemented
using optional instructions.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

---
 arch/arm/Kconfig                  |  1 +
 arch/arm/include/asm/cpufeature.h | 32 ++++++++++++++++++++
 2 files changed, 33 insertions(+)

-- 
2.7.4

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Comments

Ard Biesheuvel Oct. 29, 2016, 10:08 a.m. | #1
On 18 October 2016 at 11:52, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> Wire up the generic support for exposing CPU feature bits via the

> modalias in /sys/device/system/cpu. This allows udev to automatically

> load modules for things like crypto algorithms that are implemented

> using optional instructions.

>

> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---

>  arch/arm/Kconfig                  |  1 +

>  arch/arm/include/asm/cpufeature.h | 32 ++++++++++++++++++++

>  2 files changed, 33 insertions(+)

>


Russell,

do you have any concerns regarding this patch? If not, I will drop it
into the patch system.

Herbert,

I will resend the followup patches in this series to linux-crypto@
once this prerequisite is in place

Thanks,
Ard.


> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig

> index b5d529fdffab..1a0c6a486a9c 100644

> --- a/arch/arm/Kconfig

> +++ b/arch/arm/Kconfig

> @@ -21,6 +21,7 @@ config ARM

>         select GENERIC_ALLOCATOR

>         select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)

>         select GENERIC_CLOCKEVENTS_BROADCAST if SMP

> +       select GENERIC_CPU_AUTOPROBE

>         select GENERIC_EARLY_IOREMAP

>         select GENERIC_IDLE_POLL_SETUP

>         select GENERIC_IRQ_PROBE

> diff --git a/arch/arm/include/asm/cpufeature.h b/arch/arm/include/asm/cpufeature.h

> new file mode 100644

> index 000000000000..19c3dddd901a

> --- /dev/null

> +++ b/arch/arm/include/asm/cpufeature.h

> @@ -0,0 +1,32 @@

> +/*

> + * Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.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 __ASM_CPUFEATURE_H

> +#define __ASM_CPUFEATURE_H

> +

> +#include <asm/hwcap.h>

> +

> +/*

> + * Due to the fact that ELF_HWCAP is a 32-bit type on ARM, and given the number

> + * of optional CPU features it defines, ARM's CPU capability bits have been

> + * divided across separate elf_hwcap and elf_hwcap2 variables, each of which

> + * covers a subset of the available CPU features.

> + *

> + * Currently, only a few of those are suitable for automatic module loading

> + * (which is the primary use case of this facility) and those happen to be all

> + * covered by HWCAP2. So let's only expose those via the CPU modalias for now.

> + */

> +#define MAX_CPU_FEATURES       (8 * sizeof(elf_hwcap2))

> +#define cpu_feature(x)         ilog2(HWCAP2_ ## x)

> +

> +static inline bool cpu_have_feature(unsigned int num)

> +{

> +       return elf_hwcap2 & (1UL << num);

> +}

> +

> +#endif

> --

> 2.7.4

>

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Russell King - ARM Linux Oct. 31, 2016, 4:13 p.m. | #2
On Sat, Oct 29, 2016 at 11:08:36AM +0100, Ard Biesheuvel wrote:
> On 18 October 2016 at 11:52, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> > Wire up the generic support for exposing CPU feature bits via the

> > modalias in /sys/device/system/cpu. This allows udev to automatically

> > load modules for things like crypto algorithms that are implemented

> > using optional instructions.

> >

> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> > ---

> >  arch/arm/Kconfig                  |  1 +

> >  arch/arm/include/asm/cpufeature.h | 32 ++++++++++++++++++++

> >  2 files changed, 33 insertions(+)

> >

> 

> Russell,

> 

> do you have any concerns regarding this patch? If not, I will drop it

> into the patch system.


It's still something I need to look at... I've been offline last week,
and sort-of offline the previous week, so I'm catching up.

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Russell King - ARM Linux Jan. 2, 2017, 11:40 p.m. | #3
On Mon, Jan 02, 2017 at 09:06:04PM +0000, Ard Biesheuvel wrote:
> On 31 October 2016 at 16:13, Russell King - ARM Linux

> <linux@armlinux.org.uk> wrote:

> > On Sat, Oct 29, 2016 at 11:08:36AM +0100, Ard Biesheuvel wrote:

> >> On 18 October 2016 at 11:52, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> >> > Wire up the generic support for exposing CPU feature bits via the

> >> > modalias in /sys/device/system/cpu. This allows udev to automatically

> >> > load modules for things like crypto algorithms that are implemented

> >> > using optional instructions.

> >> >

> >> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> >> > ---

> >> >  arch/arm/Kconfig                  |  1 +

> >> >  arch/arm/include/asm/cpufeature.h | 32 ++++++++++++++++++++

> >> >  2 files changed, 33 insertions(+)

> >> >

> >>

> >> Russell,

> >>

> >> do you have any concerns regarding this patch? If not, I will drop it

> >> into the patch system.

> >

> > It's still something I need to look at... I've been offline last week,

> > and sort-of offline the previous week, so I'm catching up.

> >

> 

> Hi Russell,

> 

> Any thoughts yet?


None, and the patch is well buried now that it'll take me a while to
find... back in mid-October?  Yea, I'll have to drop everything and
go digging through my mailboxes to find it... and I'm just catching
up (again) after a week and a bit's time offline - yep, it's wonderful
timing.  Sorry, no time to look at it right now, you're not the only
one wanting my attention at the moment.

Please try again in about a week's time - don't leave it a few months,
and please include the patch.

-- 
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FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
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Ard Biesheuvel Jan. 4, 2017, 4:42 p.m. | #4
On 2 January 2017 at 23:40, Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
> On Mon, Jan 02, 2017 at 09:06:04PM +0000, Ard Biesheuvel wrote:

>> On 31 October 2016 at 16:13, Russell King - ARM Linux

>> <linux@armlinux.org.uk> wrote:

>> > On Sat, Oct 29, 2016 at 11:08:36AM +0100, Ard Biesheuvel wrote:

>> >> On 18 October 2016 at 11:52, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

>> >> > Wire up the generic support for exposing CPU feature bits via the

>> >> > modalias in /sys/device/system/cpu. This allows udev to automatically

>> >> > load modules for things like crypto algorithms that are implemented

>> >> > using optional instructions.

>> >> >

>> >> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

>> >> > ---

>> >> >  arch/arm/Kconfig                  |  1 +

>> >> >  arch/arm/include/asm/cpufeature.h | 32 ++++++++++++++++++++

>> >> >  2 files changed, 33 insertions(+)

>> >> >

>> >>

>> >> Russell,

>> >>

>> >> do you have any concerns regarding this patch? If not, I will drop it

>> >> into the patch system.

>> >

>> > It's still something I need to look at... I've been offline last week,

>> > and sort-of offline the previous week, so I'm catching up.

>> >

>>

>> Hi Russell,

>>

>> Any thoughts yet?

>

> None, and the patch is well buried now that it'll take me a while to

> find... back in mid-October?  Yea, I'll have to drop everything and

> go digging through my mailboxes to find it... and I'm just catching

> up (again) after a week and a bit's time offline - yep, it's wonderful

> timing.  Sorry, no time to look at it right now, you're not the only

> one wanting my attention at the moment.

>


No worries. It is not exactly urgent, but it is a useful enhancement
nonetheless.

> Please try again in about a week's time - don't leave it a few months,

> and please include the patch.

>


OK
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Patch hide | download patch | download mbox

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b5d529fdffab..1a0c6a486a9c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -21,6 +21,7 @@  config ARM
 	select GENERIC_ALLOCATOR
 	select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)
 	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
+	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_IDLE_POLL_SETUP
 	select GENERIC_IRQ_PROBE
diff --git a/arch/arm/include/asm/cpufeature.h b/arch/arm/include/asm/cpufeature.h
new file mode 100644
index 000000000000..19c3dddd901a
--- /dev/null
+++ b/arch/arm/include/asm/cpufeature.h
@@ -0,0 +1,32 @@ 
+/*
+ * Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.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 __ASM_CPUFEATURE_H
+#define __ASM_CPUFEATURE_H
+
+#include <asm/hwcap.h>
+
+/*
+ * Due to the fact that ELF_HWCAP is a 32-bit type on ARM, and given the number
+ * of optional CPU features it defines, ARM's CPU capability bits have been
+ * divided across separate elf_hwcap and elf_hwcap2 variables, each of which
+ * covers a subset of the available CPU features.
+ *
+ * Currently, only a few of those are suitable for automatic module loading
+ * (which is the primary use case of this facility) and those happen to be all
+ * covered by HWCAP2. So let's only expose those via the CPU modalias for now.
+ */
+#define MAX_CPU_FEATURES	(8 * sizeof(elf_hwcap2))
+#define cpu_feature(x)		ilog2(HWCAP2_ ## x)
+
+static inline bool cpu_have_feature(unsigned int num)
+{
+	return elf_hwcap2 & (1UL << num);
+}
+
+#endif