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([2001:b07:6468:f312:3577:1cfe:d98a:5fb6]) by smtp.gmail.com with ESMTPSA id c9sm4324260wmc.47.2020.02.25.06.01.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Feb 2020 06:01:52 -0800 (PST) Subject: Re: [PATCH] KVM: SVM: allocate AVIC data structures based on kvm_amd moduleparameter To: Vitaly Kuznetsov Cc: rmuncrief@humanavance.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1582617278-50338-1-git-send-email-pbonzini@redhat.com> <874kven5kv.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: Date: Tue, 25 Feb 2020 15:01:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <874kven5kv.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/02/20 14:45, Vitaly Kuznetsov wrote: >> int ret; >> + struct kvm_vcpu *vcpu = &svm->vcpu; >> >> - if (!kvm_vcpu_apicv_active(&svm->vcpu)) >> + if (!avic || !irqchip_in_kernel(vcpu->kvm)) >> return 0; >> >> ret = avic_init_backing_page(&svm->vcpu); > Out of pure curiosity, > > when irqchip_in_kernel() is false, can we still get to .update_pi_irte() > (svm_update_pi_irte()) -> get_pi_vcpu_info() -> "vcpu_info->pi_desc_addr > = __sme_set(page_to_phys((*svm)->avic_backing_page));" -> crash! or is > there anything which make this impossible? No, because kvm_arch_irqfd_allowed returns false so you cannot create any irqfd (svm_update_pi_irte is called when virt/lib/irqbypass.c finds a match between two eventfds in KVM and VFIO). Paolo