[v3] Add support for AMD hardware feedback interface

[PATCH v3 03/14] x86/cpufeatures: add X86_FEATURE_WORKLOAD_CLASS feature bit

Posted by Mario Limonciello 4 months, 3 weeks ago

From: Perry Yuan <perry.yuan@amd.com>

Add new feature bit that indicates support for workload based
heuristic feedback to OS for scheduling decisions.
When the bit set, threads are classified during runtime into
enumerated classes. The classes represent thread performance/power
characteristics that may benefit from special scheduling behaviors.

Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/kernel/cpu/scattered.c    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index cea1ed82aeb4..3e8e67b8ec7a 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -474,6 +474,7 @@
 #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* Clear branch history at vmexit using SW loop */
 #define X86_FEATURE_FAST_CPPC		(21*32 + 5) /* AMD Fast CPPC */
 #define X86_FEATURE_HETERO_CORE_TOPOLOGY	(21*32 + 6) /* Heterogeneous Core Topology */
+#define X86_FEATURE_WORKLOAD_CLASS	(21*32 + 7) /* Workload Classification */
 
 /*
  * BUG word(s)
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index 3bba55323163..b6547bab9e23 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -49,6 +49,7 @@ static const struct cpuid_bit cpuid_bits[] = {
 	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
 	{ X86_FEATURE_SMBA,		CPUID_EBX,  2, 0x80000020, 0 },
 	{ X86_FEATURE_BMEC,		CPUID_EBX,  3, 0x80000020, 0 },
+	{ X86_FEATURE_WORKLOAD_CLASS,   CPUID_EAX,  22, 0x80000021, 0 },
 	{ X86_FEATURE_PERFMON_V2,	CPUID_EAX,  0, 0x80000022, 0 },
 	{ X86_FEATURE_AMD_LBR_V2,	CPUID_EAX,  1, 0x80000022, 0 },
 	{ X86_FEATURE_AMD_LBR_PMC_FREEZE,	CPUID_EAX,  2, 0x80000022, 0 },
-- 
2.43.0

Re: [PATCH v3 03/14] x86/cpufeatures: add X86_FEATURE_WORKLOAD_CLASS feature bit

Posted by Borislav Petkov 4 months, 2 weeks ago

On Tue, Oct 15, 2024 at 04:36:34PM -0500, Mario Limonciello wrote:
> From: Perry Yuan <perry.yuan@amd.com>
> 
> Add new feature bit that indicates support for workload based
> heuristic feedback to OS for scheduling decisions.
> When the bit set, threads are classified during runtime into
> enumerated classes. The classes represent thread performance/power
> characteristics that may benefit from special scheduling behaviors.
> 
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/kernel/cpu/scattered.c    | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index cea1ed82aeb4..3e8e67b8ec7a 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -474,6 +474,7 @@
>  #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* Clear branch history at vmexit using SW loop */
>  #define X86_FEATURE_FAST_CPPC		(21*32 + 5) /* AMD Fast CPPC */
>  #define X86_FEATURE_HETERO_CORE_TOPOLOGY	(21*32 + 6) /* Heterogeneous Core Topology */
> +#define X86_FEATURE_WORKLOAD_CLASS	(21*32 + 7) /* Workload Classification */

As already discussed: X86_FEATURE_AMD_WORKLOAD_CLASS

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v3 03/14] x86/cpufeatures: add X86_FEATURE_WORKLOAD_CLASS feature bit

Posted by Mario Limonciello 4 months, 2 weeks ago

On 10/22/2024 07:42, Borislav Petkov wrote:
> On Tue, Oct 15, 2024 at 04:36:34PM -0500, Mario Limonciello wrote:
>> From: Perry Yuan <perry.yuan@amd.com>
>>
>> Add new feature bit that indicates support for workload based
>> heuristic feedback to OS for scheduling decisions.
>> When the bit set, threads are classified during runtime into
>> enumerated classes. The classes represent thread performance/power
>> characteristics that may benefit from special scheduling behaviors.
>>
>> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>>   arch/x86/include/asm/cpufeatures.h | 1 +
>>   arch/x86/kernel/cpu/scattered.c    | 1 +
>>   2 files changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
>> index cea1ed82aeb4..3e8e67b8ec7a 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -474,6 +474,7 @@
>>   #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* Clear branch history at vmexit using SW loop */
>>   #define X86_FEATURE_FAST_CPPC		(21*32 + 5) /* AMD Fast CPPC */
>>   #define X86_FEATURE_HETERO_CORE_TOPOLOGY	(21*32 + 6) /* Heterogeneous Core Topology */
>> +#define X86_FEATURE_WORKLOAD_CLASS	(21*32 + 7) /* Workload Classification */
> 
> As already discussed: X86_FEATURE_AMD_WORKLOAD_CLASS
> 

Yes; v4 does this.

https://lore.kernel.org/linux-pm/20241021180252.3531-4-mario.limonciello@amd.com/T/#u

Re: [PATCH v3 03/14] x86/cpufeatures: add X86_FEATURE_WORKLOAD_CLASS feature bit

Posted by Gautham R. Shenoy 4 months, 3 weeks ago

On Tue, Oct 15, 2024 at 04:36:34PM -0500, Mario Limonciello wrote:
> From: Perry Yuan <perry.yuan@amd.com>
> 
> Add new feature bit that indicates support for workload based
> heuristic feedback to OS for scheduling decisions.
> When the bit set, threads are classified during runtime into
> enumerated classes. The classes represent thread performance/power
> characteristics that may benefit from special scheduling behaviors.
> 
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>


> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/kernel/cpu/scattered.c    | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index cea1ed82aeb4..3e8e67b8ec7a 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -474,6 +474,7 @@
>  #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* Clear branch history at vmexit using SW loop */
>  #define X86_FEATURE_FAST_CPPC		(21*32 + 5) /* AMD Fast CPPC */
>  #define X86_FEATURE_HETERO_CORE_TOPOLOGY	(21*32 + 6) /* Heterogeneous Core Topology */
> +#define X86_FEATURE_WORKLOAD_CLASS	(21*32 + 7) /* Workload Classification */
>  
>  /*
>   * BUG word(s)
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
> index 3bba55323163..b6547bab9e23 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -49,6 +49,7 @@ static const struct cpuid_bit cpuid_bits[] = {
>  	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
>  	{ X86_FEATURE_SMBA,		CPUID_EBX,  2, 0x80000020, 0 },
>  	{ X86_FEATURE_BMEC,		CPUID_EBX,  3, 0x80000020, 0 },
> +	{ X86_FEATURE_WORKLOAD_CLASS,   CPUID_EAX,  22, 0x80000021, 0 },
>  	{ X86_FEATURE_PERFMON_V2,	CPUID_EAX,  0, 0x80000022, 0 },
>  	{ X86_FEATURE_AMD_LBR_V2,	CPUID_EAX,  1, 0x80000022, 0 },
>  	{ X86_FEATURE_AMD_LBR_PMC_FREEZE,	CPUID_EAX,  2, 0x80000022, 0 },
> -- 
> 2.43.0
>