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([2a01:e0a:59e:9d80:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id n32sm6983581wms.1.2021.11.10.07.37.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Nov 2021 07:37:04 -0800 (PST) Subject: Re: [PATCH v4 02/15] KVM: async_pf: Add helper function to check completion queue To: Gavin Shan , kvmarm@lists.cs.columbia.edu Cc: kvm@vger.kernel.org, maz@kernel.org, linux-kernel@vger.kernel.org, shan.gavin@gmail.com, Jonathan.Cameron@huawei.com, pbonzini@redhat.com, vkuznets@redhat.com, will@kernel.org References: <20210815005947.83699-1-gshan@redhat.com> <20210815005947.83699-3-gshan@redhat.com> From: Eric Auger Message-ID: <56d8dbec-a8fd-b109-0c0f-b01c1aef4741@redhat.com> Date: Wed, 10 Nov 2021 16:37:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210815005947.83699-3-gshan@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gavin, On 8/15/21 2:59 AM, Gavin Shan wrote: > This adds inline helper kvm_check_async_pf_completion_queue() to > check if there are pending completion in the queue. The empty stub > is also added on !CONFIG_KVM_ASYNC_PF so that the caller needn't > consider if CONFIG_KVM_ASYNC_PF is enabled. > > All checks on the completion queue is done by the newly added inline > function since list_empty() and list_empty_careful() are interchangeable. why is it interchangeable? > > Signed-off-by: Gavin Shan > --- > arch/x86/kvm/x86.c | 2 +- > include/linux/kvm_host.h | 10 ++++++++++ > virt/kvm/async_pf.c | 10 +++++----- > virt/kvm/kvm_main.c | 4 +--- > 4 files changed, 17 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index e5d5c5ed7dd4..7f35d9324b99 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -11591,7 +11591,7 @@ static inline bool kvm_guest_apic_has_interrupt(struct kvm_vcpu *vcpu) > > static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu) > { > - if (!list_empty_careful(&vcpu->async_pf.done)) > + if (kvm_check_async_pf_completion_queue(vcpu)) > return true; > > if (kvm_apic_has_events(vcpu)) > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 85b61a456f1c..a5f990f6dc35 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -339,12 +339,22 @@ struct kvm_async_pf { > bool notpresent_injected; > }; > > +static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu) > +{ > + return !list_empty_careful(&vcpu->async_pf.done); > +} > + > void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu); > void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu); > bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > unsigned long hva, struct kvm_arch_async_pf *arch); > int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu); > #else > +static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu) > +{ > + return false; > +} > + > static inline void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) { } > #endif > > diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c > index dd777688d14a..d145a61a046a 100644 > --- a/virt/kvm/async_pf.c > +++ b/virt/kvm/async_pf.c > @@ -70,7 +70,7 @@ static void async_pf_execute(struct work_struct *work) > kvm_arch_async_page_present(vcpu, apf); > > spin_lock(&vcpu->async_pf.lock); > - first = list_empty(&vcpu->async_pf.done); > + first = !kvm_check_async_pf_completion_queue(vcpu); > list_add_tail(&apf->link, &vcpu->async_pf.done); > apf->vcpu = NULL; > spin_unlock(&vcpu->async_pf.lock); > @@ -122,7 +122,7 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) > spin_lock(&vcpu->async_pf.lock); > } > > - while (!list_empty(&vcpu->async_pf.done)) { > + while (kvm_check_async_pf_completion_queue(vcpu)) { this is replaced by a stronger check. Please can you explain why is it equivalent? > struct kvm_async_pf *work = > list_first_entry(&vcpu->async_pf.done, > typeof(*work), link); > @@ -138,7 +138,7 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) > { > struct kvm_async_pf *work; > > - while (!list_empty_careful(&vcpu->async_pf.done) && > + while (kvm_check_async_pf_completion_queue(vcpu) && > kvm_arch_can_dequeue_async_page_present(vcpu)) { > spin_lock(&vcpu->async_pf.lock); > work = list_first_entry(&vcpu->async_pf.done, typeof(*work), > @@ -205,7 +205,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu) > struct kvm_async_pf *work; > bool first; > > - if (!list_empty_careful(&vcpu->async_pf.done)) > + if (kvm_check_async_pf_completion_queue(vcpu)) > return 0; > > work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC); > @@ -216,7 +216,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu) > INIT_LIST_HEAD(&work->queue); /* for list_del to work */ > > spin_lock(&vcpu->async_pf.lock); > - first = list_empty(&vcpu->async_pf.done); > + first = !kvm_check_async_pf_completion_queue(vcpu); > list_add_tail(&work->link, &vcpu->async_pf.done); > spin_unlock(&vcpu->async_pf.lock); > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index b50dbe269f4b..8795503651b1 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3282,10 +3282,8 @@ static bool vcpu_dy_runnable(struct kvm_vcpu *vcpu) > if (kvm_arch_dy_runnable(vcpu)) > return true; > > -#ifdef CONFIG_KVM_ASYNC_PF > - if (!list_empty_careful(&vcpu->async_pf.done)) > + if (kvm_check_async_pf_completion_queue(vcpu)) > return true; > -#endif > > return false; > } > Thanks Eric