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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id n3-20020a5d67c3000000b0021b8cd8a068sm7236417wrw.49.2022.06.21.06.17.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jun 2022 06:17:06 -0700 (PDT) From: Vitaly Kuznetsov To: Paolo Bonzini , kvm@vger.kernel.org Cc: Sean Christopherson , Maxim Levitsky , Wanpeng Li , Jim Mattson , Michael Kelley , Siddharth Chandrasekaran , Yuan Yao , linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v7 10/39] KVM: x86: hyper-v: Don't use sparse_set_to_vcpu_mask() in kvm_hv_send_ipi() In-Reply-To: <17a2e85a-a1f2-99e1-fc69-1baed2275bd5@redhat.com> References: <20220613133922.2875594-1-vkuznets@redhat.com> <20220613133922.2875594-11-vkuznets@redhat.com> <17a2e85a-a1f2-99e1-fc69-1baed2275bd5@redhat.com> Date: Tue, 21 Jun 2022 15:17:05 +0200 Message-ID: <87zgi640mm.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org Paolo Bonzini 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 >> Signed-off-by: Vitaly Kuznetsov >> --- >> 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