linux-kernel - Re: [PATCH V2 7/9] x86, amd: Factor out number of nodes calculation

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Date:	Wed, 3 Jun 2015 10:49:54 -0500
From:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
To:	Borislav Petkov <bp@...en8.de>
CC:	<dougthompson@...ssion.com>, <mchehab@....samsung.com>,
	<linux-edac@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
	Jacob Shin <jacob.w.shin@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	"Paolo Bonzini" <pbonzini@...hat.com>
Subject: Re: [PATCH V2 7/9] x86, amd: Factor out number of nodes calculation

On 6/3/2015 3:58 AM, Borislav Petkov wrote:
> On Tue, Jun 02, 2015 at 03:36:00PM -0500, Aravind Gopalakrishnan wrote:
>
>
>> +static void amd_set_num_nodes(void)
>> +{
>> +	if (cpu_has_topoext) {
>> +		u32 ecx;
>> +
>> +		ecx = cpuid_ecx(0x8000001e);
>> +		nodes_per_processor = ((ecx >> 8) & 7) + 1;
>> +	} else if (static_cpu_has(X86_FEATURE_NODEID_MSR)) {
>> +		u64 value;
>> +
>> +		rdmsrl(MSR_FAM10H_NODE_ID, value);
>> +		nodes_per_processor = ((value >> 3) & 7) + 1;
>> +	}
>> +}
>> +
>>   /*
>>    * Fixup core topology information for
>>    * (1) AMD multi-node processors
>>    *     Assumption: Number of cores in each internal node is the same.
>>    * (2) AMD processors supporting compute units
>>    */
>> -#ifdef CONFIG_X86_HT
>>   static void amd_get_topology(struct cpuinfo_x86 *c)
>>   {
>> -	u32 nodes, cores_per_cu = 1;
>> +	u32 cores_per_cu = 1;
>>   	u8 node_id;
>>   	int cpu = smp_processor_id();
>>   
>> +	amd_set_num_nodes();
> When I said, you like to complicate stuff, I wasn't joking. :-)
>
> See below for what I actually meant. Diff is ontop of the X86_HT removal
> patch from today:

*facepalm*

Sorry about that.

Thanks for fixing it.
-Aravind.

> ---
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 5bd3a99dc20b..bdca795743e8 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -19,6 +19,8 @@
>   
>   #include "cpu.h"
>   
> +static u32 nodes_per_processor = 1;
> +
>   static inline int rdmsrl_amd_safe(unsigned msr, unsigned long long *p)
>   {
>   	u32 gprs[8] = { 0 };
> @@ -291,7 +293,7 @@ static int nearby_node(int apicid)
>   #ifdef CONFIG_SMP
>   static void amd_get_topology(struct cpuinfo_x86 *c)
>   {
> -	u32 nodes, cores_per_cu = 1;
> +	u32 cores_per_cu = 1;
>   	u8 node_id;
>   	int cpu = smp_processor_id();
>   
> @@ -300,7 +302,7 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
>   		u32 eax, ebx, ecx, edx;
>   
>   		cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
> -		nodes = ((ecx >> 8) & 7) + 1;
> +		nodes_per_processor = ((ecx >> 8) & 7) + 1;
>   		node_id = ecx & 7;
>   
>   		/* get compute unit information */
> @@ -311,18 +313,18 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
>   		u64 value;
>   
>   		rdmsrl(MSR_FAM10H_NODE_ID, value);
> -		nodes = ((value >> 3) & 7) + 1;
> +		nodes_per_processor = ((value >> 3) & 7) + 1;
>   		node_id = value & 7;
>   	} else
>   		return;
>   
>   	/* fixup multi-node processor information */
> -	if (nodes > 1) {
> +	if (nodes_per_processor > 1) {
>   		u32 cores_per_node;
>   		u32 cus_per_node;
>   
>   		set_cpu_cap(c, X86_FEATURE_AMD_DCM);
> -		cores_per_node = c->x86_max_cores / nodes;
> +		cores_per_node = c->x86_max_cores / nodes_per_processor;
>   		cus_per_node = cores_per_node / cores_per_cu;
>   
>   		/* store NodeID, use llc_shared_map to store sibling info */

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