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Peter Anvin" , Paolo Bonzini , Maxim Levitsky Subject: [PATCH v3 09/12] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use Date: Mon, 2 Aug 2021 21:33:26 +0300 Message-Id: <20210802183329.2309921-10-mlevitsk@redhat.com> In-Reply-To: <20210802183329.2309921-1-mlevitsk@redhat.com> References: <20210802183329.2309921-1-mlevitsk@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vitaly Kuznetsov APICV_INHIBIT_REASON_HYPERV is currently unconditionally forced upon SynIC activation as SynIC's AutoEOI is incompatible with APICv/AVIC. It is, however, possible to track whether the feature was actually used by the guest and only inhibit APICv/AVIC when needed. TLFS suggests a dedicated 'HV_DEPRECATING_AEOI_RECOMMENDED' flag to let Windows know that AutoEOI feature should be avoided. While it's up to KVM userspace to set the flag, KVM can help a bit by exposing global APICv/AVIC enablement. Maxim: - always set HV_DEPRECATING_AEOI_RECOMMENDED in kvm_get_hv_cpuid, since this feature can be used regardless of AVIC Signed-off-by: Vitaly Kuznetsov Signed-off-by: Maxim Levitsky --- arch/x86/include/asm/kvm_host.h | 3 +++ arch/x86/kvm/hyperv.c | 27 +++++++++++++++++++++------ 2 files changed, 24 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 80323b5fb20a..55b1f79d9c43 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -988,6 +988,9 @@ struct kvm_hv { /* How many vCPUs have VP index != vCPU index */ atomic_t num_mismatched_vp_indexes; + /* How many SynICs use 'AutoEOI' feature */ + atomic_t synic_auto_eoi_used; + struct hv_partition_assist_pg *hv_pa_pg; struct kvm_hv_syndbg hv_syndbg; }; diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index b07592ca92f0..638f3c559623 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -88,6 +88,10 @@ static bool synic_has_vector_auto_eoi(struct kvm_vcpu_hv_synic *synic, static void synic_update_vector(struct kvm_vcpu_hv_synic *synic, int vector) { + struct kvm_vcpu *vcpu = hv_synic_to_vcpu(synic); + struct kvm_hv *hv = to_kvm_hv(vcpu->kvm); + int auto_eoi_old, auto_eoi_new; + if (vector < HV_SYNIC_FIRST_VALID_VECTOR) return; @@ -96,10 +100,25 @@ static void synic_update_vector(struct kvm_vcpu_hv_synic *synic, else __clear_bit(vector, synic->vec_bitmap); + auto_eoi_old = bitmap_weight(synic->auto_eoi_bitmap, 256); + if (synic_has_vector_auto_eoi(synic, vector)) __set_bit(vector, synic->auto_eoi_bitmap); else __clear_bit(vector, synic->auto_eoi_bitmap); + + auto_eoi_new = bitmap_weight(synic->auto_eoi_bitmap, 256); + + /* Hyper-V SynIC auto EOI SINTs are not compatible with APICV */ + if (!auto_eoi_old && auto_eoi_new) { + if (atomic_inc_return(&hv->synic_auto_eoi_used) == 1) + kvm_request_apicv_update(vcpu->kvm, false, + APICV_INHIBIT_REASON_HYPERV); + } else if (!auto_eoi_new && auto_eoi_old) { + if (atomic_dec_return(&hv->synic_auto_eoi_used) == 0) + kvm_request_apicv_update(vcpu->kvm, true, + APICV_INHIBIT_REASON_HYPERV); + } } static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint, @@ -933,12 +952,6 @@ int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages) synic = to_hv_synic(vcpu); - /* - * Hyper-V SynIC auto EOI SINT's are - * not compatible with APICV, so request - * to deactivate APICV permanently. - */ - kvm_request_apicv_update(vcpu->kvm, false, APICV_INHIBIT_REASON_HYPERV); synic->active = true; synic->dont_zero_synic_pages = dont_zero_synic_pages; synic->control = HV_SYNIC_CONTROL_ENABLE; @@ -2466,6 +2479,8 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, ent->eax |= HV_X64_ENLIGHTENED_VMCS_RECOMMENDED; if (!cpu_smt_possible()) ent->eax |= HV_X64_NO_NONARCH_CORESHARING; + + ent->eax |= HV_DEPRECATING_AEOI_RECOMMENDED; /* * Default number of spinlock retry attempts, matches * HyperV 2016. -- 2.26.3