linux-kernel - Re: [PATCH] x86/resctrl: Fix unneeded variable warning reported by kernel test robot

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Message-ID: <6635c607-cab2-45f4-a0fe-ff4f53b36849@intel.com>
Date: Wed, 24 Jan 2024 12:04:31 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Borislav Petkov <bp@...en8.de>
CC: Babu Moger <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
	<seanjc@...gle.com>, <jmattson@...gle.com>, <leitao@...ian.org>,
	<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
	<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>
Subject: Re: [PATCH] x86/resctrl: Fix unneeded variable warning reported by
 kernel test robot

Hi Boris,

On 1/24/2024 11:14 AM, Borislav Petkov wrote:
> On Wed, Jan 24, 2024 at 10:51:49AM -0800, Reinette Chatre wrote:
>> Thank you very much. For what it is worth, I do agree with the actual fix
>> and you can add:
>> Acked-by: Reinette Chatre <reinette.chatre@...el.com>
> 
> Ok, have a look at the below, pls, and lemme know if that's ok too.
> 
> mbm_config_write_domain() only returns 0 so it can be void. So the
> callsite doesn't need to check retval either.

Thank you very much for looking further and catching this.

You may already have taken care of this after sending this version, but I
just have a couple of nitpick comments intended to help this patch in case it
requires a clean slate from some checks. 

> 
> Thx.
> 
> ---
> From: Babu Moger <babu.moger@....com>
> Date: Wed, 24 Jan 2024 11:52:56 -0600
> Subject: [PATCH] x86/resctrl: Remove redundant variable in
>  mbm_config_write_domain()
> 
> The kernel test robot reported the following warning after
> 
>   54e35eb8611c ("x86/resctrl: Read supported bandwidth sources from CPUID").

I think a "commit" prefix is required here and below.

> 
> even though the issue is present even in the original patch which added
> this function
> 
>   92bd5a139033 ("x86/resctrl: Add interface to write mbm_total_bytes_config")
> 
>   $ make C=1 CHECK=scripts/coccicheck arch/x86/kernel/cpu/resctrl/rdtgroup.o
>   ...
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c:1621:5-8: Unneeded variable: "ret". Return "0" on line 1655
> 
> Remove the local variable 'ret'.
> 
>   [ bp: Massage commit message, make mbm_config_write_domain() void. ]
> 
> Fixes: 92bd5a139033 ("x86/resctrl: Add interface to write mbm_total_bytes_config")
> Closes: https://lore.kernel.org/oe-kbuild-all/202401241810.jbd8Ipa1-lkp@intel.com/
> Reported-by: kernel test robot <lkp@...el.com>

I do not know if this is something tip prefers but the general patch checkers prefer
that "Reported-by:" is followed by "Closes:".

> Signed-off-by: Babu Moger <babu.moger@....com>
> Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
> Acked-by: Reinette Chatre <reinette.chatre@...el.com>
> Link: https://lore.kernel.org/r/202401241810.jbd8Ipa1-lkp@intel.com
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 2b69e560b05f..c33eb77b6d70 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1614,11 +1614,10 @@ static void mon_event_config_write(void *info)
>  	wrmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, 0);
>  }
>  
> -static int mbm_config_write_domain(struct rdt_resource *r,
> +static void mbm_config_write_domain(struct rdt_resource *r,
>  				   struct rdt_domain *d, u32 evtid, u32 val)

This shifts the alignment slightly to no longer match the open parenthesis.

>  {
>  	struct mon_config_info mon_info = {0};
> -	int ret = 0;
>  
>  	/*
>  	 * Read the current config value first. If both are the same then
> @@ -1627,7 +1626,7 @@ static int mbm_config_write_domain(struct rdt_resource *r,
>  	mon_info.evtid = evtid;
>  	mondata_config_read(d, &mon_info);
>  	if (mon_info.mon_config == val)
> -		goto out;
> +		return;
>  
>  	mon_info.mon_config = val;
>  
> @@ -1650,9 +1649,6 @@ static int mbm_config_write_domain(struct rdt_resource *r,
>  	 * mbm_local and mbm_total counts for all the RMIDs.
>  	 */
>  	resctrl_arch_reset_rmid_all(r, d);
> -
> -out:
> -	return ret;
>  }
>  
>  static int mon_config_write(struct rdt_resource *r, char *tok, u32 evtid)
> @@ -1661,7 +1657,6 @@ static int mon_config_write(struct rdt_resource *r, char *tok, u32 evtid)
>  	char *dom_str = NULL, *id_str;
>  	unsigned long dom_id, val;
>  	struct rdt_domain *d;
> -	int ret = 0;
>  
>  next:
>  	if (!tok || tok[0] == '\0')
> @@ -1690,9 +1685,7 @@ static int mon_config_write(struct rdt_resource *r, char *tok, u32 evtid)
>  
>  	list_for_each_entry(d, &r->domains, list) {
>  		if (d->id == dom_id) {
> -			ret = mbm_config_write_domain(r, d, evtid, val);
> -			if (ret)
> -				return -EINVAL;
> +			mbm_config_write_domain(r, d, evtid, val);
>  			goto next;
>  		}
>  	}

The core changes look good to me. Thank you very much for creating this fix.

Reinette