linux-kernel - arch/arm64/kvm/vgic/vgic-mmio.c:1094:3: warning: variable 'len' is used uninitialized whenever 'if' condition is false

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Message-ID: <202508152354.FWDol8gs-lkp@intel.com>
Date: Fri, 15 Aug 2025 23:50:14 +0200
From: kernel test robot <lkp@...el.com>
To: Sascha Bischoff <Sascha.Bischoff@....com>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
	linux-kernel@...r.kernel.org, Oliver Upton <oliver.upton@...ux.dev>,
	Timothy Hayes <timothy.hayes@....com>
Subject: arch/arm64/kvm/vgic/vgic-mmio.c:1094:3: warning: variable 'len' is
 used uninitialized whenever 'if' condition is false

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   d0efc9e4276cda07c2f76652d240b165c30b05b8
commit: c017e49ed1381001ba7a6521daae8f968b11cf09 KVM: arm64: gic-v5: Support GICv3 compat
date:   5 weeks ago
config: arm64-randconfig-2002-20250814 (https://download.01.org/0day-ci/archive/20250815/202508152354.FWDol8gs-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 7d886fab74d4037d654d02bed24dd97c0ba863d6)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250815/202508152354.FWDol8gs-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/202508152354.FWDol8gs-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/arm64/kvm/vgic/vgic-mmio.c:1094:3: warning: variable 'len' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
    1094 |                 BUG_ON(1);
         |                 ^~~~~~~~~
   include/asm-generic/bug.h:71:36: note: expanded from macro 'BUG_ON'
      71 | #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
         |                                    ^~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:47:23: note: expanded from macro 'unlikely'
      47 | #  define unlikely(x)   (__branch_check__(x, 0, __builtin_constant_p(x)))
         |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/arm64/kvm/vgic/vgic-mmio.c:1102:12: note: uninitialized use occurs here
    1102 |                                        len, &io_device->dev);
         |                                        ^~~
   arch/arm64/kvm/vgic/vgic-mmio.c:1094:3: note: remove the 'if' if its condition is always true
    1094 |                 BUG_ON(1);
         |                 ^
   include/asm-generic/bug.h:71:32: note: expanded from macro 'BUG_ON'
      71 | #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
         |                                ^
   arch/arm64/kvm/vgic/vgic-mmio.c:1084:18: note: initialize the variable 'len' to silence this warning
    1084 |         unsigned int len;
         |                         ^
         |                          = 0
   1 warning generated.


vim +1094 arch/arm64/kvm/vgic/vgic-mmio.c

fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1079  
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1080  int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address,
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1081  			     enum vgic_type type)
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1082  {
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1083  	struct vgic_io_device *io_device = &kvm->arch.vgic.dist_iodev;
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1084  	unsigned int len;
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1085  
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1086  	switch (type) {
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1087  	case VGIC_V2:
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1088  		len = vgic_v2_init_dist_iodev(io_device);
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1089  		break;
ed9b8cefa91695 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2015-12-01  1090  	case VGIC_V3:
ed9b8cefa91695 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2015-12-01  1091  		len = vgic_v3_init_dist_iodev(io_device);
ed9b8cefa91695 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2015-12-01  1092  		break;
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26  1093  	default:
fb848db39661a1 virt/kvm/arm/vgic/vgic-mmio.c Andre Przywara 2016-04-26 @1094  		BUG_ON(1);

:::::: The code at line 1094 was first introduced by commit
:::::: fb848db39661a1243f6ae939ef7e9251a765b972 KVM: arm/arm64: vgic-new: Add GICv2 MMIO handling framework

:::::: TO: Andre Przywara <andre.przywara@....com>
:::::: CC: Christoffer Dall <christoffer.dall@...aro.org>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki