linux-kernel - Re: [PATCH v7 5/5] powerpc/hv-24x7: Update post_mobility

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Date:   Tue, 5 May 2020 12:27:00 +0530
From:   kajoljain <kjain@...ux.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>, acme@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, sukadev@...ux.vnet.ibm.com
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        anju@...ux.vnet.ibm.com, maddy@...ux.vnet.ibm.com,
        ravi.bangoria@...ux.ibm.com, peterz@...radead.org,
        yao.jin@...ux.intel.com, ak@...ux.intel.com, jolsa@...nel.org,
        kan.liang@...ux.intel.com, jmario@...hat.com,
        alexander.shishkin@...ux.intel.com, mingo@...nel.org,
        paulus@...abs.org, namhyung@...nel.org, mpetlan@...hat.com,
        gregkh@...uxfoundation.org, benh@...nel.crashing.org,
        mamatha4@...ux.vnet.ibm.com, mark.rutland@....com,
        tglx@...utronix.de
Subject: Re: [PATCH v7 5/5] powerpc/hv-24x7: Update post_mobility_fixup() to
 handle migration



On 4/29/20 5:07 PM, Michael Ellerman wrote:
> Kajol Jain <kjain@...ux.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@...ux.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.
> 

Hi Michael,
	Thanks for reviewing the patch. Is something like this you are suggesting. Please
let me know if my understanding is fine.

+#ifndef CONFIG_HV_PERF_CTRS
+#define read_sys_info_pseries() 
+#endif

Thanks,
Kajol Jain
> cheers
>