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Thu, 21 Jun 2018 13:50:54 -0700 (PDT) Date: Thu, 21 Jun 2018 13:50:53 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Michal Hocko cc: Andrew Morton , Tetsuo Handa , "Aneesh Kumar K.V" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch] mm, oom: fix unnecessary killing of additional processes In-Reply-To: <20180621074537.GC10465@dhcp22.suse.cz> Message-ID: References: <20180615065541.GA24039@dhcp22.suse.cz> <20180619083316.GB13685@dhcp22.suse.cz> <20180620130311.GM13685@dhcp22.suse.cz> <20180621074537.GC10465@dhcp22.suse.cz> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 Jun 2018, Michal Hocko wrote: > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > > index 6bcecc325e7e..ac08f5d711be 100644 > > > --- a/arch/x86/kvm/x86.c > > > +++ b/arch/x86/kvm/x86.c > > > @@ -7203,8 +7203,9 @@ static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu) > > > kvm_x86_ops->load_eoi_exitmap(vcpu, eoi_exit_bitmap); > > > } > > > > > > -void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm, > > > - unsigned long start, unsigned long end) > > > +int kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm, > > > + unsigned long start, unsigned long end, > > > + bool blockable) > > > { > > > unsigned long apic_address; > > > > > > @@ -7215,6 +7216,8 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm, > > > apic_address = gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT); > > > if (start <= apic_address && apic_address < end) > > > kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD); > > > + > > > + return 0; > > > } > > > > > > void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu) > > > > Auditing the first change in the patch, this is incorrect because > > kvm_make_all_cpus_request() for KVM_REQ_APIC_PAGE_RELOAD can block in > > kvm_kick_many_cpus() and that is after kvm_make_request() has been done. > > I would have to check the code closer. But doesn't > kvm_make_all_cpus_request call get_cpu which is preempt_disable? I > definitely plan to talk to respective maintainers about these changes of > course. > preempt_disable() is required because it calls kvm_kick_many_cpus() with wait == true because KVM_REQ_APIC_PAGE_RELOAD sets KVM_REQUEST_WAIT and thus the smp_call_function_many() is going to block until all cpus can run ack_flush().