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

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Date: Wed, 24 Jan 2024 20:14:29 +0100
From: Borislav Petkov <bp@...en8.de>
To: Reinette Chatre <reinette.chatre@...el.com>
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

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.

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").

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>
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)
 {
 	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;
 		}
 	}
-- 
2.43.0

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette