linux-kernel - Re: [PATCH v8 07/10] powerpc/perf: PMU functions for Core IMC and hotplugging

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Message-Id: <87wp9fdifx.fsf@linux.vnet.ibm.com>
Date:   Wed, 17 May 2017 17:57:22 +1000
From:   Stewart Smith <stewart@...ux.vnet.ibm.com>
To:     Anju T Sudhakar <anju@...ux.vnet.ibm.com>, mpe@...erman.id.au
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        ego@...ux.vnet.ibm.com, bsingharora@...il.com, anton@...ba.org,
        sukadev@...ux.vnet.ibm.com, mikey@...ling.org, dja@...ens.net,
        eranian@...gle.com, hemant@...ux.vnet.ibm.com,
        maddy@...ux.vnet.ibm.com, anju@...ux.vnet.ibm.com
Subject: Re: [PATCH v8 07/10] powerpc/perf: PMU functions for Core IMC and hotplugging

Anju T Sudhakar <anju@...ux.vnet.ibm.com> writes:
> --- a/arch/powerpc/include/asm/imc-pmu.h
> +++ b/arch/powerpc/include/asm/imc-pmu.h
> @@ -24,6 +24,7 @@
>   */
>  #define IMC_MAX_CHIPS			32
>  #define IMC_MAX_PMUS			32
> +#define IMC_MAX_CORES			32
>
>  /*
>   * This macro is used for memory buffer allocation of
> @@ -38,6 +39,11 @@
>  #define IMC_NEST_MAX_PAGES		64
>
>  /*
> + * IMC Core engine expects 8K bytes of memory for counter collection.
> + */
> +#define IMC_CORE_COUNTER_MEM		8192

Any reason for this not to be in the device tree?

This is the size of memory that Linux needs to give OPAL, so the size of
that should probably come from OPAL rather than Linux.

Otherwise, if in the future, we had a counter with an offset greater
than 8192 in, we'd have no way to detect that and we'd fail silently by
overwriting memory.

-- 
Stewart Smith
OPAL Architect, IBM.