Paolo Bonzini <pbonzini@xxxxxxxxxx> writes:
> 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@xxxxxxxxxx>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> ---
>> 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?
Hm, with Hyper-V PV IPI hypercall vCPUs are also addressed by their
VP_IDs, not by their APIC ids so similar to Hyper-V PV TLB flush we need
to convert the supplied set (either flat u64 bitmask of VP_IDs for
non-EX hypercall or a sparse set for -EX).
> And since patch 12 only affects the sparse banks, the patch does not
> have any other dependency. Is this correct?
>
This patch introduces hv_is_vp_in_sparse_set() with its first user:
kvm_hv_send_ipi_to_many(). Later in the series, hv_is_vp_in_sparse_set()
gets a second user: kvm_hv_flush_tlb() for 'nested' case where we
actually have to traverse all vCPUs checking *nested* VP_IDs (as KVM
doesn't currently keep a convenient L2-VP_ID-to-kvm-vcpu-id mapping.
> 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;
>
--
Vitaly
