linux-kernel - Re: [PATCH 2/4] KVM: Add tlb remote flush callback in kvm_x86

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Date:   Tue, 3 Jul 2018 10:39:57 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Tianyu Lan <Tianyu.Lan@...rosoft.com>
Cc:     kbuild-all@...org, Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: Re: [PATCH 2/4] KVM: Add tlb remote flush callback in kvm_x86_ops.

Hi Tianyu,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on kvm/linux-next]
[also build test ERROR on v4.18-rc3 next-20180702]
[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/Tianyu-Lan/KVM-x86-hyper-V-Introduce-PV-guest-address-space-mapping-flush-support/20180703-012046
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
config: powerpc-defconfig (attached as .config)
compiler: powerpc64-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=powerpc 

All errors (new ones prefixed by >>):

   arch/powerpc/kvm/../../../virt/kvm/kvm_main.c: In function 'kvm_flush_remote_tlbs':
>> arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:265:6: error: 'kvm_x86_ops' undeclared (first use in this function); did you mean 'kvm_xive_ops'?
     if (kvm_x86_ops->tlb_remote_flush &&
         ^~~~~~~~~~~
         kvm_xive_ops
   arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:265:6: note: each undeclared identifier is reported only once for each function it appears in

vim +265 arch/powerpc/kvm/../../../virt/kvm/kvm_main.c

   255	
   256	#ifndef CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL
   257	void kvm_flush_remote_tlbs(struct kvm *kvm)
   258	{
   259		long dirty_count;
   260	
   261		/*
   262		 * Call tlb_remote_flush first and go back old way when
   263		 * return failure.
   264		 */
 > 265		if (kvm_x86_ops->tlb_remote_flush &&
   266		    !kvm_x86_ops->tlb_remote_flush(kvm))
   267			return;
   268	
   269		/*
   270		 * Read tlbs_dirty before setting KVM_REQ_TLB_FLUSH in
   271		 * kvm_make_all_cpus_request.
   272		 */
   273		dirty_count = smp_load_acquire(&kvm->tlbs_dirty);
   274	
   275		/*
   276		 * We want to publish modifications to the page tables before reading
   277		 * mode. Pairs with a memory barrier in arch-specific code.
   278		 * - x86: smp_mb__after_srcu_read_unlock in vcpu_enter_guest
   279		 * and smp_mb in walk_shadow_page_lockless_begin/end.
   280		 * - powerpc: smp_mb in kvmppc_prepare_to_enter.
   281		 *
   282		 * There is already an smp_mb__after_atomic() before
   283		 * kvm_make_all_cpus_request() reads vcpu->mode. We reuse that
   284		 * barrier here.
   285		 */
   286		if (kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
   287			++kvm->stat.remote_tlb_flush;
   288		cmpxchg(&kvm->tlbs_dirty, dirty_count, 0);
   289	}
   290	EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
   291	#endif
   292	

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