On Thu, Apr 07, 2022, 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.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> arch/x86/kvm/hyperv.c | 35 ++++++++++++++++++++++++-----------
> 1 file changed, 24 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index d7bcdf87b90c..918642bcdbd0 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1746,6 +1746,23 @@ 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 / 64, (unsigned long *)&valid_bank_mask))
'64' really, really, really needs a #define. I assume this is the same '64' that's
used to check the var_cnt when getting the sparse_banks.
> + return false;
> +
> + for_each_set_bit(bank, (unsigned long *)&valid_bank_mask,
> + KVM_HV_MAX_SPARSE_VCPU_SET_BITS) {
> + if (bank == vp_id / 64)
> + break;
> + sbank++;
> + }
> +
> + return test_bit(vp_id % 64, (unsigned long *)&sparse_banks[sbank]);
> +}
