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    SubjectRe: [PATCH v2 1/2] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts
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    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 (&&).

    > + __clear_bit(i, &bitmap);
    > + continue;
    > + }
    > + }
    > +
    > + dest_vcpus = hweight16(bitmap);
    > +
    > + if (dest_vcpus != 0) {
    > + idx = kvm_vector_2_index(irq->vector,
    > + dest_vcpus, &bitmap, 16);
    > +
    > + bitmap = 0;
    > + __set_bit(idx-1, &bitmap);
    > + }
    > }
    > -
    > - bitmap = (l >= 0) ? 1 << l : 0;
    > }
    > }
    >
    > diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
    > index fde8e35d..6890ef0 100644
    > --- a/arch/x86/kvm/lapic.h
    > +++ b/arch/x86/kvm/lapic.h
    > @@ -170,4 +170,6 @@ void wait_lapic_expire(struct kvm_vcpu *vcpu);
    >
    > bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
    > struct kvm_vcpu **dest_vcpu);
    > +int kvm_vector_2_index(u32 vector, u32 dest_vcpus,
    > + const unsigned long *bitmap, u32 bitmap_size);
    > #endif
    > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > index 4a6eff1..fb47730 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -118,6 +118,9 @@ module_param(tsc_tolerance_ppm, uint, S_IRUGO | S_IWUSR);
    > unsigned int lapic_timer_advance_ns = 0;
    > module_param(lapic_timer_advance_ns, uint, S_IRUGO | S_IWUSR);
    >
    > +bool __read_mostly enable_vector_hashing = 1;
    > +module_param(enable_vector_hashing, bool, S_IRUGO);
    > +
    > static bool backwards_tsc_observed = false;
    >
    > #define KVM_NR_SHARED_MSRS 16
    > @@ -8165,6 +8168,12 @@ int kvm_arch_update_irqfd_routing(struct kvm *kvm, unsigned int host_irq,
    > return kvm_x86_ops->update_pi_irte(kvm, host_irq, guest_irq, set);
    > }
    >
    > +bool kvm_vector_hashing_enabled(void)
    > +{
    > + return enable_vector_hashing;
    > +}
    > +EXPORT_SYMBOL_GPL(kvm_vector_hashing_enabled);
    > +
    > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
    > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
    > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);
    > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
    > index f2afa5f..04bd0f9 100644
    > --- a/arch/x86/kvm/x86.h
    > +++ b/arch/x86/kvm/x86.h
    > @@ -179,6 +179,7 @@ int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data);
    > int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
    > bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
    > int page_num);
    > +bool kvm_vector_hashing_enabled(void);
    >
    > #define KVM_SUPPORTED_XCR0 (XFEATURE_MASK_FP | XFEATURE_MASK_SSE \
    > | XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
    >


    --
    best regards
    yang


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