Messages in this thread |  | | Subject | Re: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts | From | Yang Zhang <> | Date | Mon, 21 Dec 2015 10:06:18 +0800 |
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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(-) >>> >>> diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c >>> index 84b96d3..c8c5f61 100644 >>> --- a/arch/x86/kvm/irq_comm.c >>> +++ b/arch/x86/kvm/irq_comm.c >>> @@ -32,6 +32,7 @@ >>> #include "ioapic.h" >>> >>> #include "lapic.h" >>> +#include "x86.h" >>> >>> static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e, >>> struct kvm *kvm, int irq_source_id, int level, >>> @@ -53,8 +54,10 @@ static int kvm_set_ioapic_irq(struct >> kvm_kernel_irq_routing_entry *e, >>> int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, >>> struct kvm_lapic_irq *irq, unsigned long *dest_map) >>> { >>> - int i, r = -1; >>> + int i, r = -1, idx = 0; >>> struct kvm_vcpu *vcpu, *lowest = NULL; >>> + unsigned long dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]; >>> + unsigned int dest_vcpus = 0; >>> >>> if (irq->dest_mode == 0 && irq->dest_id == 0xff && >>> kvm_lowest_prio_delivery(irq)) { >>> @@ -65,6 +68,8 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct >> kvm_lapic *src, >>> if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map)) >>> return r; >>> >>> + memset(dest_vcpu_bitmap, 0, sizeof(dest_vcpu_bitmap)); >>> + >>> kvm_for_each_vcpu(i, vcpu, kvm) { >>> if (!kvm_apic_present(vcpu)) >>> continue; >>> @@ -78,13 +83,25 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct >> kvm_lapic *src, >>> r = 0; >>> r += kvm_apic_set_irq(vcpu, irq, dest_map); >>> } else if (kvm_lapic_enabled(vcpu)) { >>> - if (!lowest) >>> - lowest = vcpu; >>> - else if (kvm_apic_compare_prio(vcpu, lowest) < 0) >>> - lowest = vcpu; >>> + if (!kvm_vector_hashing_enabled()) { >>> + if (!lowest) >>> + lowest = vcpu; >>> + else if (kvm_apic_compare_prio(vcpu, lowest) < >> 0) >>> + lowest = vcpu; >>> + } else { >>> + __set_bit(vcpu->vcpu_id, dest_vcpu_bitmap); >>> + dest_vcpus++; >>> + } >>> } >>> } >>> >>> + if (dest_vcpus != 0) { >>> + idx = kvm_vector_2_index(irq->vector, dest_vcpus, >>> + dest_vcpu_bitmap, KVM_MAX_VCPUS); >>> + >>> + lowest = kvm_get_vcpu(kvm, idx - 1); >>> + } >>> + >>> if (lowest) >>> r = kvm_apic_set_irq(lowest, irq, dest_map); >>> >>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c >>> index ecd4ea1..e29001f 100644 >>> --- a/arch/x86/kvm/lapic.c >>> +++ b/arch/x86/kvm/lapic.c >>> @@ -678,6 +678,22 @@ bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, >> struct kvm_lapic *source, >>> } >>> } >>> >>> +int kvm_vector_2_index(u32 vector, u32 dest_vcpus, >>> + const unsigned long *bitmap, u32 bitmap_size) >>> +{ >>> + u32 mod; >>> + int i, idx = 0; >>> + >>> + mod = vector % dest_vcpus; >>> + >>> + for (i = 0; i <= mod; i++) { >>> + idx = find_next_bit(bitmap, bitmap_size, idx) + 1; >>> + BUG_ON(idx > bitmap_size); >>> + } >>> + >>> + return idx; >>> +} >>> + >>> 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?
> > Thanks, > Feng >
-- best regards yang
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