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

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Date:   Tue, 05 May 2020 17:05:52 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     kajoljain <kjain@...ux.ibm.com>, 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

kajoljain <kjain@...ux.ibm.com> writes:
> 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

It should be an empty static inline. So more like:

#ifdef CONFIG_HV_PERF_CTRS
void read_sys_info_pseries(void);
#else
static inline void read_sys_info_pseries(void) { }
#endif

cheers