Re: [PATCH 2/2] KVM: x86: Clear X2APIC_ICR_UNUSED_12 after APIC-write VM-exit

[kernel test robot <lkp@intel.com>]

Hi Tao,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 708283abf896dd4853e673cc8cba70acaf9bf4ea]

url:    https://github.com/intel-lab-lkp/linux/commits/Tao-Su/x86-apic-Introduce-X2APIC_ICR_UNUSED_12-for-x2APIC-mode/20230904-093801
base:   708283abf896dd4853e673cc8cba70acaf9bf4ea
patch link:    https://lore.kernel.org/r/20230904013555.725413-3-tao1.su%40linux.intel.com
patch subject: [PATCH 2/2] KVM: x86: Clear X2APIC_ICR_UNUSED_12 after APIC-write VM-exit
config: x86_64-randconfig-003-20230904 (https://download.01.org/0day-ci/archive/20230904/202309041224.CDj6t1BN-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230904/202309041224.CDj6t1BN-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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309041224.CDj6t1BN-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/x86/kvm/lapic.c:2445:30: warning: variable 'val' is uninitialized when used here [-Wuninitialized]
                   kvm_x2apic_icr_write(apic, val);
                                              ^~~
   arch/x86/kvm/lapic.c:2435:9: note: initialize the variable 'val' to silence this warning
           u64 val;
                  ^
                   = 0
   1 warning generated.


vim +/val +2445 arch/x86/kvm/lapic.c

  2430	
  2431	/* emulate APIC access in a trap manner */
  2432	void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset)
  2433	{
  2434		struct kvm_lapic *apic = vcpu->arch.apic;
  2435		u64 val;
  2436	
  2437		/*
  2438		 * ICR is a single 64-bit register when x2APIC is enabled.  For legacy
  2439		 * xAPIC, ICR writes need to go down the common (slightly slower) path
  2440		 * to get the upper half from ICR2.
  2441		 *
  2442		 * TODO: optimize to just emulate side effect w/o one more write
  2443		 */
  2444		if (apic_x2apic_mode(apic) && offset == APIC_ICR) {
> 2445			kvm_x2apic_icr_write(apic, val);
  2446		} else {
  2447			val = kvm_lapic_get_reg(apic, offset);
  2448			kvm_lapic_reg_write(apic, offset, (u32)val);
  2449		}
  2450	}
  2451	EXPORT_SYMBOL_GPL(kvm_apic_write_nodecode);
  2452	

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