linux-kernel - Re: [PATCH 1/4] KVM: VMX: extract __pi_post

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Date:   Wed, 7 Jun 2017 05:27:01 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Longpeng <longpeng2@...wei.com>,
        Huangweidong <weidong.huang@...wei.com>,
        Gonglei <arei.gonglei@...wei.com>,
        wangxin <wangxinxin.wang@...wei.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 1/4] KVM: VMX: extract __pi_post_block

Hi Paolo,

[auto build test WARNING on kvm/linux-next]
[also build test WARNING on v4.12-rc4 next-20170606]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Paolo-Bonzini/VT-d-PI-fixes/20170607-042637
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
config: i386-randconfig-x012-201723 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   In file included from arch/x86/include/asm/atomic.h:7:0,
                    from include/linux/atomic.h:4,
                    from include/linux/mm_types_task.h:12,
                    from include/linux/mm_types.h:4,
                    from arch/x86/kvm/irq.h:25,
                    from arch/x86/kvm/vmx.c:19:
   arch/x86/kvm/vmx.c: In function '__pi_post_block':
>> arch/x86/include/asm/cmpxchg.h:129:2: warning: '__ret' is used uninitialized in this function [-Wuninitialized]
     __ret;        \
     ^~~~~
   arch/x86/include/asm/cmpxchg.h:86:21: note: '__ret' was declared here
     __typeof__(*(ptr)) __ret;     \
                        ^
>> arch/x86/include/asm/cmpxchg.h:133:2: note: in expansion of macro '__raw_cmpxchg'
     __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
     ^~~~~~~~~~~~~
>> arch/x86/include/asm/cmpxchg.h:148:2: note: in expansion of macro '__cmpxchg'
     __cmpxchg(ptr, old, new, sizeof(*(ptr)))
     ^~~~~~~~~
>> arch/x86/kvm/vmx.c:11242:11: note: in expansion of macro 'cmpxchg'
     } while (cmpxchg(&pi_desc->control, old.control,
              ^~~~~~~
--
   In file included from arch/x86/include/asm/atomic.h:7:0,
                    from include/linux/atomic.h:4,
                    from include/linux/mm_types_task.h:12,
                    from include/linux/mm_types.h:4,
                    from arch/x86//kvm/irq.h:25,
                    from arch/x86//kvm/vmx.c:19:
   arch/x86//kvm/vmx.c: In function '__pi_post_block':
>> arch/x86/include/asm/cmpxchg.h:129:2: warning: '__ret' is used uninitialized in this function [-Wuninitialized]
     __ret;        \
     ^~~~~
   arch/x86/include/asm/cmpxchg.h:86:21: note: '__ret' was declared here
     __typeof__(*(ptr)) __ret;     \
                        ^
>> arch/x86/include/asm/cmpxchg.h:133:2: note: in expansion of macro '__raw_cmpxchg'
     __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
     ^~~~~~~~~~~~~
>> arch/x86/include/asm/cmpxchg.h:148:2: note: in expansion of macro '__cmpxchg'
     __cmpxchg(ptr, old, new, sizeof(*(ptr)))
     ^~~~~~~~~
   arch/x86//kvm/vmx.c:11242:11: note: in expansion of macro 'cmpxchg'
     } while (cmpxchg(&pi_desc->control, old.control,
              ^~~~~~~

vim +/cmpxchg +11242 arch/x86/kvm/vmx.c

 11226	
 11227		do {
 11228			old.control = new.control = pi_desc->control;
 11229	
 11230			dest = cpu_physical_id(vcpu->cpu);
 11231	
 11232			if (x2apic_enabled())
 11233				new.ndst = dest;
 11234			else
 11235				new.ndst = (dest << 8) & 0xFF00;
 11236	
 11237			/* Allow posting non-urgent interrupts */
 11238			new.sn = 0;
 11239	
 11240			/* set 'NV' to 'notification vector' */
 11241			new.nv = POSTED_INTR_VECTOR;
 11242		} while (cmpxchg(&pi_desc->control, old.control,
 11243				new.control) != old.control);
 11244	
 11245		if(vcpu->pre_pcpu != -1) {
 11246			spin_lock_irqsave(
 11247				&per_cpu(blocked_vcpu_on_cpu_lock,
 11248				vcpu->pre_pcpu), flags);
 11249			list_del(&vcpu->blocked_vcpu_list);
 11250			spin_unlock_irqrestore(

---
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