linux-kernel - [tip:x86/microcode 1/1] arch/x86/kernel/cpu/microcode/amd.c:714:6: warning: variable 'equiv_id' is used uninitialized whenever 'if' condition is false

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Message-ID: <202407291815.gJBST0P3-lkp@intel.com>
Date: Mon, 29 Jul 2024 19:04:51 +0800
From: kernel test robot <lkp@...el.com>
To: Borislav Petkov <bp@...en8.de>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [tip:x86/microcode 1/1] arch/x86/kernel/cpu/microcode/amd.c:714:6:
 warning: variable 'equiv_id' is used uninitialized whenever 'if' condition
 is false

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/microcode
head:   94838d230a6c835ced1bad06b8759e0a5f19c1d3
commit: 94838d230a6c835ced1bad06b8759e0a5f19c1d3 [1/1] x86/microcode/AMD: Use the family,model,stepping encoded in the patch ID
config: i386-buildonly-randconfig-001-20240729 (https://download.01.org/0day-ci/archive/20240729/202407291815.gJBST0P3-lkp@intel.com/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240729/202407291815.gJBST0P3-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202407291815.gJBST0P3-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/cpu/microcode/amd.c:714:6: warning: variable 'equiv_id' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
     714 |         if (x86_family(bsp_cpuid_1_eax) < 0x17) {
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/cpu/microcode/amd.c:720:31: note: uninitialized use occurs here
     720 |         return cache_find_patch(uci, equiv_id);
         |                                      ^~~~~~~~
   arch/x86/kernel/cpu/microcode/amd.c:714:2: note: remove the 'if' if its condition is always true
     714 |         if (x86_family(bsp_cpuid_1_eax) < 0x17) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/cpu/microcode/amd.c:706:14: note: initialize the variable 'equiv_id' to silence this warning
     706 |         u16 equiv_id;
         |                     ^
         |                      = 0
   1 warning generated.


vim +714 arch/x86/kernel/cpu/microcode/amd.c

   701	
   702	static struct ucode_patch *find_patch(unsigned int cpu)
   703	{
   704		struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
   705		u32 rev, dummy __always_unused;
   706		u16 equiv_id;
   707	
   708		/* fetch rev if not populated yet: */
   709		if (!uci->cpu_sig.rev) {
   710			rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
   711			uci->cpu_sig.rev = rev;
   712		}
   713	
 > 714		if (x86_family(bsp_cpuid_1_eax) < 0x17) {
   715			equiv_id = find_equiv_id(&equiv_table, uci->cpu_sig.sig);
   716			if (!equiv_id)
   717				return NULL;
   718		}
   719	
   720		return cache_find_patch(uci, equiv_id);
   721	}
   722	

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https://github.com/intel/lkp-tests/wiki