[PATCH] MIPS: elf_hwcap: Export microMIPS and vz

[PATCH] MIPS: elf_hwcap: Export microMIPS and vz

[Jiaxun Yang]

After further discussion with userland library develpoer,
we addressed another two ASEs that can be used runtimely in programs.

Export them in hwcap as well to benefit userspace programs.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: <stable@vger.kernel.org> # 4.4+
---
 arch/mips/include/uapi/asm/hwcap.h | 2 ++
 arch/mips/kernel/cpu-probe.c       | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/mips/include/uapi/asm/hwcap.h b/arch/mips/include/uapi/asm/hwcap.h
index 1ade1daa4921..e1a9bac62149 100644
--- a/arch/mips/include/uapi/asm/hwcap.h
+++ b/arch/mips/include/uapi/asm/hwcap.h
@@ -17,5 +17,7 @@
 #define HWCAP_LOONGSON_MMI  (1 << 11)
 #define HWCAP_LOONGSON_EXT  (1 << 12)
 #define HWCAP_LOONGSON_EXT2 (1 << 13)
+#define HWCAP_MIPS_MICROMIPS (1 << 14)
+#define HWCAP_MIPS_VZ       (1 << 15)
 
 #endif /* _UAPI_ASM_HWCAP_H */
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index f521cbf934e7..11e853d88aae 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -2213,8 +2213,13 @@ void cpu_probe(void)
 	if (cpu_has_loongson_ext2)
 		elf_hwcap |= HWCAP_LOONGSON_EXT2;
 
-	if (cpu_has_vz)
+	if (cpu_has_mmips)
+		elf_hwcap |= HWCAP_MIPS_MICROMIPS;
+
+	if (cpu_has_vz) {
+		elf_hwcap |= HWCAP_MIPS_VZ;
 		cpu_probe_vz(c);
+	}
 
 	cpu_probe_vmbits(c);
 
-- 
2.23.0

Re: [PATCH] MIPS: elf_hwcap: Export microMIPS and vz

[Paul Burton]

Hi Jiaxun,

On Wed, Oct 23, 2019 at 11:25:51PM +0800, Jiaxun Yang wrote:
> After further discussion with userland library develpoer,
> we addressed another two ASEs that can be used runtimely in programs.
> 
> Export them in hwcap as well to benefit userspace programs.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> Cc: <stable@vger.kernel.org> # 4.4+
> ---
>  arch/mips/include/uapi/asm/hwcap.h | 2 ++
>  arch/mips/kernel/cpu-probe.c       | 7 ++++++-
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/mips/include/uapi/asm/hwcap.h b/arch/mips/include/uapi/asm/hwcap.h
> index 1ade1daa4921..e1a9bac62149 100644
> --- a/arch/mips/include/uapi/asm/hwcap.h
> +++ b/arch/mips/include/uapi/asm/hwcap.h
> @@ -17,5 +17,7 @@
>  #define HWCAP_LOONGSON_MMI  (1 << 11)
>  #define HWCAP_LOONGSON_EXT  (1 << 12)
>  #define HWCAP_LOONGSON_EXT2 (1 << 13)
> +#define HWCAP_MIPS_MICROMIPS (1 << 14)
> +#define HWCAP_MIPS_VZ       (1 << 15)

What's the motivation for exposing VZ? Userland can't actually use it
without something like KVM, which already exposes a means of detecting
whether VZ is supported (try the creating a VM of type KVM_VM_MIPS_VZ &
see if it works). I'm not sure what userland would be able to do with
this information in AT_HWCAP.

Thanks,
    Paul

>  #endif /* _UAPI_ASM_HWCAP_H */
> diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
> index f521cbf934e7..11e853d88aae 100644
> --- a/arch/mips/kernel/cpu-probe.c
> +++ b/arch/mips/kernel/cpu-probe.c
> @@ -2213,8 +2213,13 @@ void cpu_probe(void)
>  	if (cpu_has_loongson_ext2)
>  		elf_hwcap |= HWCAP_LOONGSON_EXT2;
>  
> -	if (cpu_has_vz)
> +	if (cpu_has_mmips)
> +		elf_hwcap |= HWCAP_MIPS_MICROMIPS;
> +
> +	if (cpu_has_vz) {
> +		elf_hwcap |= HWCAP_MIPS_VZ;
>  		cpu_probe_vz(c);
> +	}
>  
>  	cpu_probe_vmbits(c);
>  
> -- 
> 2.23.0
> 

Re: [PATCH] MIPS: elf_hwcap: Export microMIPS and vz

[Jiaxun Yang]

于 2019年10月24日 GMT+08:00 下午12:06:24, Paul Burton <paulburton@kernel.org> 写到:
>Hi Jiaxun,
>
>On Wed, Oct 23, 2019 at 11:25:51PM +0800, Jiaxun Yang wrote:
>> After further discussion with userland library develpoer,
>> we addressed another two ASEs that can be used runtimely in programs.
>> 
>> Export them in hwcap as well to benefit userspace programs.
>> 
>> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
>> Cc: <stable@vger.kernel.org> # 4.4+
>> ---
>>  arch/mips/include/uapi/asm/hwcap.h | 2 ++
>>  arch/mips/kernel/cpu-probe.c       | 7 ++++++-
>>  2 files changed, 8 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/mips/include/uapi/asm/hwcap.h
>b/arch/mips/include/uapi/asm/hwcap.h
>> index 1ade1daa4921..e1a9bac62149 100644
>> --- a/arch/mips/include/uapi/asm/hwcap.h
>> +++ b/arch/mips/include/uapi/asm/hwcap.h
>> @@ -17,5 +17,7 @@
>>  #define HWCAP_LOONGSON_MMI  (1 << 11)
>>  #define HWCAP_LOONGSON_EXT  (1 << 12)
>>  #define HWCAP_LOONGSON_EXT2 (1 << 13)
>> +#define HWCAP_MIPS_MICROMIPS (1 << 14)
>> +#define HWCAP_MIPS_VZ       (1 << 15)
>
>What's the motivation for exposing VZ? Userland can't actually use it
>without something like KVM, which already exposes a means of detecting
>whether VZ is supported (try the creating a VM of type KVM_VM_MIPS_VZ &
>see if it works). I'm not sure what userland would be able to do with
>this information in AT_HWCAP

Hi Paul,

Well, that was preposed by a kvm developer from Loongson. They want to use it to implement CPU_AUTOPROBE and load required modules automatically.

As they said they will submit KVM support to mainline later, I'm just occupied a place for them.

Out of tree commit:

http://cgit.loongnix.org/cgit/linux-3.10/commit/?id=4db9301cca3b49358d46fd0da67c01ab2ae4a3e3

-- 
Jiaxun Yang

Re: [PATCH] MIPS: elf_hwcap: Export microMIPS and vz

[Sergei Shtylyov]

Hello!

On 23.10.2019 18:25, Jiaxun Yang wrote:

> After further discussion with userland library develpoer,

    Developer. :-)

> we addressed another two ASEs that can be used runtimely in programs.

    I'm afraid there's no such word "runtimely". It's "at run time" probably...

> Export them in hwcap as well to benefit userspace programs.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> Cc: <stable@vger.kernel.org> # 4.4+
[...]

MBR, Sergei