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SubjectRe: [PATCH v7 10/39] KVM: x86: hyper-v: Don't use sparse_set_to_vcpu_mask() in kvm_hv_send_ipi()
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On 6/13/22 15:38, Vitaly Kuznetsov wrote:
> 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(-)

I'm a bit confused by this patch being in this series.

Just to be clear, PV IPI does *not* support the VP_ID, right? And since
patch 12 only affects the sparse banks, the patch does not have any
other dependency. Is this correct?

Paolo

> 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;

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