linux-kernel - Re: [PATCH v2 2/5] KVM: x86: hyperv: introduce vp_index_to_vcpu

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Date:   Fri, 29 Jun 2018 02:49:43 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kbuild-all@...org, kvm@...r.kernel.org, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Roman Kagan <rkagan@...tuozzo.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        Mohammed Gamal <mmorsy@...hat.com>,
        Cathy Avery <cavery@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] KVM: x86: hyperv: introduce vp_index_to_vcpu_idx
 mapping

Hi Vitaly,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on kvm/linux-next]
[also build test WARNING on v4.18-rc2 next-20180628]
[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/Vitaly-Kuznetsov/KVM-x86-hyperv-PV-IPI-support-for-Windows-guests/20180629-011544
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

>> arch/x86/kvm/hyperv.c:156:15: sparse: incompatible types in comparison expression (different address spaces)
   arch/x86/kvm/hyperv.c:195:15: sparse: incompatible types in comparison expression (different address spaces)

vim +156 arch/x86/kvm/hyperv.c

   136	
   137	static u32 vp_idx_to_vcpu_idx(struct kvm *kvm, u32 vp_idx)
   138	{
   139		struct kvm_hv *hv = &kvm->arch.hyperv;
   140		u32 vcpu_idx = U32_MAX, tmp_vp_idx;
   141		int l_index = 0, r_index, tmp_index;
   142		struct vp_idx_map *map;
   143	
   144		/*
   145		 * Make an educated guess: vp_idx is initialized to == vcpu_idx, it
   146		 * stays this way unless changed by userspace.
   147		 */
   148		if (vp_idx < KVM_MAX_VCPUS) {
   149			struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, vp_idx);
   150	
   151			if (vcpu && vcpu_to_hv_vcpu(vcpu)->vp_index == vp_idx)
   152				return vp_idx;
   153		}
   154	
   155		rcu_read_lock();
 > 156		map = rcu_dereference(hv->vp_idx_map);
   157		if (!map)
   158			goto unlock;
   159	
   160		r_index = map->len - 1;
   161	
   162		while (r_index >= l_index) {
   163			tmp_index = (r_index + l_index)/2;
   164			tmp_vp_idx = map->vp_idx_elem[tmp_index].vp_idx;
   165	
   166			if (tmp_vp_idx == vp_idx) {
   167				vcpu_idx = map->vp_idx_elem[tmp_index].vcpu_idx;
   168				break;
   169			} else if (tmp_vp_idx < vp_idx) {
   170				l_index = tmp_index + 1;
   171			} else /* (tmp_vp_idx > vp_idx) */ {
   172				r_index = tmp_index - 1;
   173			}
   174		};
   175	
   176	unlock:
   177		rcu_read_unlock();
   178	
   179		return vcpu_idx;
   180	}
   181	

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