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SubjectRE: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts
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> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
> owner@vger.kernel.org] On Behalf Of Yang Zhang
> Sent: Monday, December 21, 2015 10:06 AM
> To: Wu, Feng <feng.wu@intel.com>; pbonzini@redhat.com;
> rkrcmar@redhat.com
> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-
> priority interrupts
>
> On 2015/12/21 9:50, Wu, Feng wrote:
> >
> >
> >> -----Original Message-----
> >> From: Yang Zhang [mailto:yang.zhang.wz@gmail.com]
> >> Sent: Monday, December 21, 2015 9:46 AM
> >> To: Wu, Feng <feng.wu@intel.com>; pbonzini@redhat.com;
> >> rkrcmar@redhat.com
> >> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org
> >> 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@intel.com>
> >>> ---
> >>> 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?

Thanks,
Feng


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