Re: [kvm:kvm-async-pf-int-5.8 3/6] arch/x86/kernel/kvm.c:330:6: warning: Variable 'pa' is reassigned a value before the old one has been used.

[Vitaly Kuznetsov <vkuznets@redhat.com>]

kernel test robot <lkp@intel.com> writes:

> tree:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git kvm-async-pf-int-5.8
> head:   62a9576cc07b7dcba951aaa00d6a55933c49367e
> commit: b1d405751cd5792856b1b8333aafaca6bf09ccbb [3/6] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery
> compiler: gcc-9 (Debian 9.3.0-13) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
>
> cppcheck warnings: (new ones prefixed by >>)
>
>>> arch/x86/kernel/kvm.c:330:6: warning: Variable 'pa' is reassigned a value before the old one has been used. [redundantAssignment]
>      pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
>         ^
>    arch/x86/kernel/kvm.c:326:0: note: Variable 'pa' is reassigned a value before the old one has been used.
>      u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
>    ^
>    arch/x86/kernel/kvm.c:330:6: note: Variable 'pa' is reassigned a value before the old one has been used.
>      pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
>         ^
>
> vim +/pa +330 arch/x86/kernel/kvm.c
>
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  322  
> ed3cf15271fa15 Nicholas Krause    2015-05-20  323  static void kvm_guest_cpu_init(void)
> fd10cde9294f73 Gleb Natapov       2010-10-14  324  {
> b1d405751cd579 Vitaly Kuznetsov   2020-05-25  325  	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) {
> b1d405751cd579 Vitaly Kuznetsov   2020-05-25  326  		u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));

Leftover from previous version, this should just be 'u64 pa;'

> ef68017eb5704e Andy Lutomirski    2020-02-28  327  
> ef68017eb5704e Andy Lutomirski    2020-02-28  328  		WARN_ON_ONCE(!static_branch_likely(&kvm_async_pf_enabled));
> ef68017eb5704e Andy Lutomirski    2020-02-28  329  
> ef68017eb5704e Andy Lutomirski    2020-02-28 @330  		pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
> b1d405751cd579 Vitaly Kuznetsov   2020-05-25  331  		pa |= KVM_ASYNC_PF_ENABLED | KVM_ASYNC_PF_DELIVERY_AS_INT;
> 52a5c155cf79f1 Wanpeng Li         2017-07-13  332  
> fe2a3027e74e40 Radim Krčmář       2018-02-01  333  		if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT))
> fe2a3027e74e40 Radim Krčmář       2018-02-01  334  			pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
> fe2a3027e74e40 Radim Krčmář       2018-02-01  335  
> b1d405751cd579 Vitaly Kuznetsov   2020-05-25  336  		wrmsrl(MSR_KVM_ASYNC_PF_INT, HYPERVISOR_CALLBACK_VECTOR);
> b1d405751cd579 Vitaly Kuznetsov   2020-05-25  337  
> 52a5c155cf79f1 Wanpeng Li         2017-07-13  338  		wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
> 89cbc76768c2fa Christoph Lameter  2014-08-17  339  		__this_cpu_write(apf_reason.enabled, 1);
> 6bca69ada4bc20 Thomas Gleixner    2020-03-07  340  		pr_info("KVM setup async PF for cpu %d\n", smp_processor_id());
> fd10cde9294f73 Gleb Natapov       2010-10-14  341  	}
> d910f5c1064d7f Glauber Costa      2011-07-11  342  
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  343  	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  344  		unsigned long pa;
> 6bca69ada4bc20 Thomas Gleixner    2020-03-07  345  
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  346  		/* Size alignment is implied but just to make it explicit. */
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  347  		BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
> 89cbc76768c2fa Christoph Lameter  2014-08-17  348  		__this_cpu_write(kvm_apic_eoi, 0);
> 89cbc76768c2fa Christoph Lameter  2014-08-17  349  		pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
> 5dfd486c4750c9 Dave Hansen        2013-01-22  350  			| KVM_MSR_ENABLED;
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  351  		wrmsrl(MSR_KVM_PV_EOI_EN, pa);
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  352  	}
> ab9cf4996bb989 Michael S. Tsirkin 2012-06-24  353  
> d910f5c1064d7f Glauber Costa      2011-07-11  354  	if (has_steal_clock)
> d910f5c1064d7f Glauber Costa      2011-07-11  355  		kvm_register_steal_time();
> fd10cde9294f73 Gleb Natapov       2010-10-14  356  }
> fd10cde9294f73 Gleb Natapov       2010-10-14  357  
>
> :::::: The code at line 330 was first introduced by commit
> :::::: ef68017eb5704eb2b0577c3aa6619e13caf2b59f x86/kvm: Handle async page faults directly through do_page_fault()
>
> :::::: TO: Andy Lutomirski <luto@kernel.org>
> :::::: CC: Thomas Gleixner <tglx@linutronix.de>
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>

-- 
Vitaly