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    Subject[PATCH v7 10/39] KVM: x86: hyper-v: Don't use sparse_set_to_vcpu_mask() in kvm_hv_send_ipi()
    Date
    Get rid of on-stack allocation of vcpu_mask and optimize kvm_hv_send_ipi()
    for a smaller number of vCPUs in the request. When Hyper-V TLB flush
    is in use, HvSendSyntheticClusterIpi{,Ex} calls are not commonly used to
    send IPIs to a large number of vCPUs (and are rarely used in general).

    Introduce hv_is_vp_in_sparse_set() to directly check if the specified
    VP_ID is present in sparse vCPU set.

    Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
    Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    ---
    arch/x86/kvm/hyperv.c | 37 ++++++++++++++++++++++++++-----------
    1 file changed, 26 insertions(+), 11 deletions(-)

    diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
    index f41153c71beb..269a5fcca31b 100644
    --- a/arch/x86/kvm/hyperv.c
    +++ b/arch/x86/kvm/hyperv.c
    @@ -1747,6 +1747,25 @@ static void sparse_set_to_vcpu_mask(struct kvm *kvm, u64 *sparse_banks,
    }
    }

    +static bool hv_is_vp_in_sparse_set(u32 vp_id, u64 valid_bank_mask, u64 sparse_banks[])
    +{
    + int bank, sbank = 0;
    +
    + if (!test_bit(vp_id / HV_VCPUS_PER_SPARSE_BANK,
    + (unsigned long *)&valid_bank_mask))
    + return false;
    +
    + for_each_set_bit(bank, (unsigned long *)&valid_bank_mask,
    + KVM_HV_MAX_SPARSE_VCPU_SET_BITS) {
    + if (bank == vp_id / HV_VCPUS_PER_SPARSE_BANK)
    + break;
    + sbank++;
    + }
    +
    + return test_bit(vp_id % HV_VCPUS_PER_SPARSE_BANK,
    + (unsigned long *)&sparse_banks[sbank]);
    +}
    +
    struct kvm_hv_hcall {
    u64 param;
    u64 ingpa;
    @@ -2029,8 +2048,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    ((u64)hc->rep_cnt << HV_HYPERCALL_REP_COMP_OFFSET);
    }

    -static void kvm_send_ipi_to_many(struct kvm *kvm, u32 vector,
    - unsigned long *vcpu_bitmap)
    +static void kvm_hv_send_ipi_to_many(struct kvm *kvm, u32 vector,
    + u64 *sparse_banks, u64 valid_bank_mask)
    {
    struct kvm_lapic_irq irq = {
    .delivery_mode = APIC_DM_FIXED,
    @@ -2040,7 +2059,10 @@ static void kvm_send_ipi_to_many(struct kvm *kvm, u32 vector,
    unsigned long i;

    kvm_for_each_vcpu(i, vcpu, kvm) {
    - if (vcpu_bitmap && !test_bit(i, vcpu_bitmap))
    + if (sparse_banks &&
    + !hv_is_vp_in_sparse_set(kvm_hv_get_vpindex(vcpu),
    + valid_bank_mask,
    + sparse_banks))
    continue;

    /* We fail only when APIC is disabled */
    @@ -2053,7 +2075,6 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    struct kvm *kvm = vcpu->kvm;
    struct hv_send_ipi_ex send_ipi_ex;
    struct hv_send_ipi send_ipi;
    - DECLARE_BITMAP(vcpu_mask, KVM_MAX_VCPUS);
    u64 valid_bank_mask;
    u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS];
    u32 vector;
    @@ -2115,13 +2136,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR))
    return HV_STATUS_INVALID_HYPERCALL_INPUT;

    - if (all_cpus) {
    - kvm_send_ipi_to_many(kvm, vector, NULL);
    - } else {
    - sparse_set_to_vcpu_mask(kvm, sparse_banks, valid_bank_mask, vcpu_mask);
    -
    - kvm_send_ipi_to_many(kvm, vector, vcpu_mask);
    - }
    + kvm_hv_send_ipi_to_many(kvm, vector, all_cpus ? NULL : sparse_banks, valid_bank_mask);

    ret_success:
    return HV_STATUS_SUCCESS;
    --
    2.35.3
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