linux-kernel - Re: [PATCH v3 2/2] amd: uncore: Get correct number of cores sharing last level cache

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Date:   Wed, 14 Jun 2017 16:23:51 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Janakarajan Natarajan <Janakarajan.Natarajan@....com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: Re: [PATCH v3 2/2] amd: uncore: Get correct number of cores sharing
 last level cache

On Tue, Jun 13, 2017 at 10:58:28AM -0500, Janakarajan Natarajan wrote:
> In Family 17h, the number of cores sharing a cache level is obtained
> from the Cache Properties CPUID leaf (0x8000001d) by passing in the
> cache level in ECX. In prior families, a cache level of 2 was used to
> determine this information.
> 
> To get the right information, irrespective of Family, iterate over
> the cache levels using CPUID 0x8000001d. The last level cache is the
> last value to return a non-zero value in EAX.
> 
> Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@....com>
> ---
>  arch/x86/events/amd/uncore.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
> index e34f8a6..a0b33de 100644
> --- a/arch/x86/events/amd/uncore.c
> +++ b/arch/x86/events/amd/uncore.c
> @@ -400,11 +400,24 @@ static int amd_uncore_cpu_starting(unsigned int cpu)
>  
>  	if (amd_uncore_llc) {
>  		unsigned int apicid = cpu_data(cpu).apicid;
> -		unsigned int nshared;
> +		unsigned int nshared, subleaf, prev_eax = 0;
>  
>  		uncore = *per_cpu_ptr(amd_uncore_llc, cpu);
> -		cpuid_count(0x8000001d, 2, &eax, &ebx, &ecx, &edx);
> -		nshared = ((eax >> 14) & 0xfff) + 1;
> +		/*
> +		 * Iterate over Cache Topology Definition leaves until no
> +		 * more cache descriptions are available.
> +		 */
> +		for(subleaf = 0; subleaf < 5; subleaf++) {


ERROR: space required before the open parenthesis '('
#51: FILE: arch/x86/events/amd/uncore.c:410:
+               for(subleaf = 0; subleaf < 5; subleaf++) {

Please integrate scripts/checkpatch.pl in your patch creation workflow.
Some of the warnings/errors *actually* make sense.

Thanks.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.