linux-kernel - Re: [PATCH 2/2] x86/CPU/AMD: Derive CPU topology from CPUID Fn0xB

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Date:   Tue, 27 Mar 2018 19:04:45 +0700
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, bp@...e.de
Subject: Re: [PATCH 2/2] x86/CPU/AMD: Derive CPU topology from CPUID Fn0xB

Hi All,

On 3/26/18 3:05 PM, Suravee Suthikulpanit wrote:
> Derive topology information from Extended Topology Enumeration
> (CPUID Fn0x0000000B) when the information is available.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>   arch/x86/kernel/cpu/amd.c | 16 ++++++++++++----
>   1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 2c1a9f2..2b40144 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -338,10 +338,18 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
>   			c->cu_id = ebx & 0xff;
>   
>   		if (c->x86 >= 0x17) {
> -			c->cpu_core_id = ebx & 0xff;
> +			int err = detect_extended_topology(c);
>   
> -			if (smp_num_siblings > 1)
> -				c->x86_max_cores /= smp_num_siblings;
> +			if (err) {
> +				c->cpu_core_id = ebx & 0xff;
> +
> +				if (smp_num_siblings > 1)
> +					c->x86_max_cores /= smp_num_siblings;
> +			} else {
> +				int bits = get_count_order(c->x86_max_cores);
> +
> +				c->x86_coreid_bits = get_count_order(bits);
> +			}
>   		}

I made a mistake here in the attempt to clean up the code. I'll send out V2 to fix this.

Thanks,
Suravee