[V2 PATCH] arm64: restore bogomips information in /proc/cpuinfo

[V2 PATCH] arm64: restore bogomips information in /proc/cpuinfo

[Yang Shi]

As what Pavel Machek reported [1], some userspace applications depend on
bogomips showed by /proc/cpuinfo.

Although there is much less legacy impact on aarch64 than arm, but it does
break libvirt.

Basically, this patch reverts commit 326b16db9f69fd0d279be873c6c00f88c0a4aad5
("arm64: delay: don't bother reporting bogomips in /proc/cpuinfo"), but with
some tweak due to context change.

[1] https://lkml.org/lkml/2015/1/4/132

Acked-by: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org> #3.12+
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
V2 --> V1:
* Remove double new line and unnecessary bogomips sum info

 arch/arm64/kernel/cpuinfo.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 706679d..212ae63 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -30,6 +30,7 @@
 #include <linux/seq_file.h>
 #include <linux/sched.h>
 #include <linux/smp.h>
+#include <linux/delay.h>
 
 /*
  * In case the boot CPU is hotpluggable, we record its initial state and
@@ -112,6 +113,10 @@ static int c_show(struct seq_file *m, void *v)
 		 */
 		seq_printf(m, "processor\t: %d\n", i);
 
+		seq_printf(m, "BogoMIPS\t: %lu.%02lu\n",
+			   loops_per_jiffy / (500000UL/HZ),
+			   loops_per_jiffy / (5000UL/HZ) % 100);
+
 		/*
 		 * Dump out the common processor features in a single line.
 		 * Userspace should read the hwcaps with getauxval(AT_HWCAP)
-- 
2.0.2

[V2 PATCH] arm64: restore bogomips information in /proc/cpuinfo

[Catalin Marinas]

On Wed, Nov 18, 2015 at 10:48:55AM -0800, Yang Shi wrote:
> As what Pavel Machek reported [1], some userspace applications depend on
> bogomips showed by /proc/cpuinfo.
> 
> Although there is much less legacy impact on aarch64 than arm, but it does
> break libvirt.
> 
> Basically, this patch reverts commit 326b16db9f69fd0d279be873c6c00f88c0a4aad5
> ("arm64: delay: don't bother reporting bogomips in /proc/cpuinfo"), but with
> some tweak due to context change.
> 
> [1] https://lkml.org/lkml/2015/1/4/132
> 
> Acked-by: Will Deacon <will.deacon@arm.com>
> Cc: <stable@vger.kernel.org> #3.12+
> Signed-off-by: Yang Shi <yang.shi@linaro.org>

Patch applied as a fix for stable, basically returning back to the
pre-3.12 behaviour. If there is a need for some more useful information
here, it can be done as an additional patch, though without cc: stable.

Thanks.

-- 
Catalin

[V2 PATCH] arm64: restore bogomips information in /proc/cpuinfo

[Shi, Yang]

On 11/19/2015 9:59 AM, Catalin Marinas wrote:
> On Wed, Nov 18, 2015 at 10:48:55AM -0800, Yang Shi wrote:
>> As what Pavel Machek reported [1], some userspace applications depend on
>> bogomips showed by /proc/cpuinfo.
>>
>> Although there is much less legacy impact on aarch64 than arm, but it does
>> break libvirt.
>>
>> Basically, this patch reverts commit 326b16db9f69fd0d279be873c6c00f88c0a4aad5
>> ("arm64: delay: don't bother reporting bogomips in /proc/cpuinfo"), but with
>> some tweak due to context change.
>>
>> [1] https://lkml.org/lkml/2015/1/4/132
>>
>> Acked-by: Will Deacon <will.deacon@arm.com>
>> Cc: <stable@vger.kernel.org> #3.12+
>> Signed-off-by: Yang Shi <yang.shi@linaro.org>
>
> Patch applied as a fix for stable, basically returning back to the
> pre-3.12 behaviour. If there is a need for some more useful information
> here, it can be done as an additional patch, though without cc: stable.

Thanks. This approach sounds safer to usersapce.

Yang

>
> Thanks.
>