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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Kajol Jain <kjain@linux.ibm.com>, acme@kernel.org,
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Subject: Re: [PATCH v7 5/5] powerpc/hv-24x7: Update post_mobility_fixup() to handle migration
In-Reply-To: <20200327063642.26175-6-kjain@linux.ibm.com>
References: <20200327063642.26175-1-kjain@linux.ibm.com> <20200327063642.26175-6-kjain@linux.ibm.com>
Date:   Wed, 29 Apr 2020 21:37:12 +1000
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Kajol Jain <kjain@linux.ibm.com> writes:
> Function 'read_sys_info_pseries()' is added to get system parameter
> values like number of sockets and chips per socket.
> and it gets these details via rtas_call with token
> "PROCESSOR_MODULE_INFO".
>
> Incase lpar migrate from one system to another, system
> parameter details like chips per sockets or number of sockets might
> change. So, it needs to be re-initialized otherwise, these values
> corresponds to previous system values.
> This patch adds a call to 'read_sys_info_pseries()' from
> 'post-mobility_fixup()' to re-init the physsockets and physchips values.
>
> Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/mobility.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
> index b571285f6c14..226accd6218b 100644
> --- a/arch/powerpc/platforms/pseries/mobility.c
> +++ b/arch/powerpc/platforms/pseries/mobility.c
> @@ -371,6 +371,18 @@ void post_mobility_fixup(void)
>  	/* Possibly switch to a new RFI flush type */
>  	pseries_setup_rfi_flush();
>  
> +	/*
> +	 * Incase lpar migrate from one system to another, system

In case an LPAR migrates

> +	 * parameter details like chips per sockets and number of sockets
> +	 * might change. So, it needs to be re-initialized otherwise these
                             ^                                       ^
                             they need                               the
> +	 * values corresponds to previous system.
                  ^
                  will correspond to the

> +	 * Here, adding a call to read_sys_info_pseries() declared in

Adding is the wrong tense in a comment. When someone reads the comment
the code has already been added. Past tense would be right, but really
the comment shouldn't say what you did, it should say why.

> +	 * platforms/pseries/pseries.h to re-init the physsockets and
> +	 * physchips value.

Call read_sys_info_pseries() to reinitialise the values.

> +	 */
> +	if (IS_ENABLED(CONFIG_HV_PERF_CTRS) && IS_ENABLED(CONFIG_PPC_RTAS))
> +		read_sys_info_pseries();

The RTAS check is not needed. pseries always selects RTAS.

You shouldn't need the IS_ENABLED() check here though, do it with an
empty version in the header when CONFIG_HV_PERF_CTRS is not enabled.

cheers