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Date: Tue, 7 Feb 2012 14:13:33 +0800 From: Liu ping fan <kernelfans@...il.com> To: Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp> Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, avi@...hat.com, aliguori@...ibm.com, gleb@...hat.com, mtosatti@...hat.com, xiaoguangrong.eric@...il.com, jan.kiszka@....de Subject: Re: [PATCH v8] kvm: make vcpu life cycle separated from kvm instance 2012/2/7 Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>: > (2012/02/07 11:34), Liu Ping Fan wrote: > >> static int kvm_vcpu_release(struct inode *inode, struct file *filp) > > Is this a hot path? > If no, do you really need to pre-allocate the space for the next vcpus? > No, it is not a hot path, I will try your way in next version. >> { >> + int i; >> struct kvm_vcpu *vcpu = filp->private_data; >> + struct kvm *kvm = vcpu->kvm; >> + struct kvm_vcpu *vcpus_next; >> + filp->private_data = NULL; >> + >> + for (i = 0; i< atomic_read(&kvm->online_vcpus); i++) { >> + if (vcpu == kvm->vcpus+i) >> + break; >> + } >> + mutex_lock(&kvm->lock); >> + vcpus_next = kvm->vcpus_array + >> + ((kvm->vcpus - kvm->vcpus_array) ? 0 : KVM_MAX_VCPUS); >> + >> + memset(vcpus_next, 0, KVM_MAX_VCPUS*sizeof(struct kvm_vcpu *)); >> + memcpy(vcpus_next, kvm->vcpus, i*sizeof(struct kvm_vcpu *)); >> + memcpy(vcpus_next+i, kvm->vcpus+i+1, >> + (atomic_read(&kvm->online_vcpus)-i)*sizeof(struct kvm_vcpu *)); >> + atomic_dec(&kvm->online_vcpus); >> + /* Removed vcpu can not be seen from vcpus[] */ > > This comment is confusing. > I mean after assigning pointer, vcpu which to be removed can not be seen from vcpus[]. I will fix this comment. >> + rcu_assign_pointer(kvm->vcpus, vcpus_next); >> + mutex_unlock(&kvm->lock); >> + >> + synchronize_rcu(); >> >> - kvm_put_kvm(vcpu->kvm); >> + /* vcpu is out of list,drop it safely */ > > Ditto. > > Do you mean something like > "now that there is no reader of it we can safely free this" ? > Yes, that is exactly what I mean Thanks and regards, ping fan > (Please do not trust me: I am not a native English speaker as you know.) > >> + kvm_vcpu_destruct(vcpu); >> return 0; >> } > > > Takuya -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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