Hi Radim/Paolo, > -----Original Message----- > From: Yang Zhang [mailto:yang.zhang.wz@xxxxxxxxx] > Sent: Tuesday, December 22, 2015 3:14 PM > To: Wu, Feng <feng.wu@xxxxxxxxx>; pbonzini@xxxxxxxxxx; > rkrcmar@xxxxxxxxxx > Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Jiang Liu > (jiang.liu@xxxxxxxxxxxxxxx) <jiang.liu@xxxxxxxxxxxxxxx> > Subject: Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest- > priority interrupts > > On 2015/12/22 14:59, Wu, Feng wrote: > > > > > >> -----Original Message----- > >> From: Yang Zhang [mailto:yang.zhang.wz@xxxxxxxxx] > >> Sent: Tuesday, December 22, 2015 2:49 PM > >> To: Wu, Feng <feng.wu@xxxxxxxxx>; pbonzini@xxxxxxxxxx; > >> rkrcmar@xxxxxxxxxx > >> Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Jiang Liu > >> (jiang.liu@xxxxxxxxxxxxxxx) <jiang.liu@xxxxxxxxxxxxxxx> > >> Subject: Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest- > >> priority interrupts > >> > >>>>>> > >>>>>> On 2015/12/16 9:37, Feng Wu wrote: > >>>>>>> Use vector-hashing to deliver lowest-priority interrupts, As an > >>>>>>> example, modern Intel CPUs in server platform use this method to > >>>>>>> handle lowest-priority interrupts. > >>>>>>> > >>>>>>> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx> > >>>>>>> --- > >>>>>>> arch/x86/kvm/irq_comm.c | 27 ++++++++++++++++++----- > >>>>>>> arch/x86/kvm/lapic.c | 57 > >>>>>> ++++++++++++++++++++++++++++++++++++++++--------- > >>>>>>> arch/x86/kvm/lapic.h | 2 ++ > >>>>>>> arch/x86/kvm/x86.c | 9 ++++++++ > >>>>>>> arch/x86/kvm/x86.h | 1 + > >>>>>>> 5 files changed, 81 insertions(+), 15 deletions(-) > >>>>>>> > >>>>>>> bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct > kvm_lapic > >>>> *src, > >>>>>>> struct kvm_lapic_irq *irq, int *r, unsigned long > >> *dest_map) > >>>>>>> { > >>>>>>> @@ -731,17 +747,38 @@ bool kvm_irq_delivery_to_apic_fast(struct > kvm > >>>>>> *kvm, struct kvm_lapic *src, > >>>>>>> dst = map->logical_map[cid]; > >>>>>>> > >>>>>>> if (kvm_lowest_prio_delivery(irq)) { > >>>>>>> - int l = -1; > >>>>>>> - for_each_set_bit(i, &bitmap, 16) { > >>>>>>> - if (!dst[i]) > >>>>>>> - continue; > >>>>>>> - if (l < 0) > >>>>>>> - l = i; > >>>>>>> - else if (kvm_apic_compare_prio(dst[i]- > >vcpu, > >>>>>> dst[l]->vcpu) < 0) > >>>>>>> - l = i; > >>>>>>> + if (!kvm_vector_hashing_enabled()) { > >>>>>>> + int l = -1; > >>>>>>> + for_each_set_bit(i, &bitmap, 16) { > >>>>>>> + if (!dst[i]) > >>>>>>> + continue; > >>>>>>> + if (l < 0) > >>>>>>> + l = i; > >>>>>>> + else if > (kvm_apic_compare_prio(dst[i]- > >>>>>>> vcpu, dst[l]->vcpu) < 0) > >>>>>>> + l = i; > >>>>>>> + } > >>>>>>> + bitmap = (l >= 0) ? 1 << l : 0; > >>>>>>> + } else { > >>>>>>> + int idx = 0; > >>>>>>> + unsigned int dest_vcpus = 0; > >>>>>>> + > >>>>>>> + for_each_set_bit(i, &bitmap, 16) { > >>>>>>> + if (!dst[i] > >>>>>> && !kvm_lapic_enabled(dst[i]->vcpu)) { > >>>>>> > >>>>>> It should be or(||) not and (&&). > >>>>> > >>>>> Oh, you are right! My negligence! Thanks for pointing this out, Yang! > >>>> > >>>> btw, i think the kvm_lapic_enabled check is wrong here? Why need it here? > >>> > >>> If the lapic is not enabled, I think we cannot recognize it as a candidate, can > >> we? > >>> Maybe Radim can confirm this, Radim, what is your option? > >> > >> Lapic can be disable by hw or sw. Here we only need to check the hw is > >> enough which is already covered while injecting the interrupt into > >> guest. I remember we(Glab, Macelo and me) have discussed it several ago, > >> but i cannot find the mail thread. > > > > But if the lapic is disabled by software, we cannot still inject interrupts to > > it, can we? > > Yes, We cannot inject the normal interrupt. But this already covered by > current logic and add a check here seems meaningless. Conversely, it may > do bad thing.. > Let's wait for Radim/Paolo's opinions about this. Thanks, Feng -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
