From: Paolo Bonzini <pbonzini@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org
Cc: Wanpeng Li <wanpengli@tencent.com>,
Thomas Gleixner <tglx@linutronix.de>,
Joerg Roedel <joro@8bytes.org>, Borislav Petkov <bp@alien8.de>,
Sean Christopherson <seanjc@google.com>,
Jim Mattson <jmattson@google.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@vger.kernel.org>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v3 09/12] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use
Date: Tue, 3 Aug 2021 11:01:10 +0200 [thread overview]
Message-ID: <4209384b-68f3-a0d2-24da-3b047422f114@redhat.com> (raw)
In-Reply-To: <20210802183329.2309921-10-mlevitsk@redhat.com>
On 02/08/21 20:33, Maxim Levitsky wrote:
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>
> 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 <vkuznets@redhat.com>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
> 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.
>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
next prev parent reply other threads:[~2021-08-03 9:01 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-02 18:33 [PATCH v3 00/12] My AVIC patch queue Maxim Levitsky
2021-08-02 18:33 ` [PATCH v3 01/12] Revert "KVM: x86/mmu: Allow zap gfn range to operate under the mmu read lock" Maxim Levitsky
2021-08-03 8:05 ` Paolo Bonzini
2021-08-03 15:11 ` Sean Christopherson
2021-08-03 17:29 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 02/12] KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_range Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 03/12] KVM: x86/mmu: rename try_async_pf to kvm_faultin_pfn Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 04/12] KVM: x86/mmu: allow kvm_faultin_pfn to return page fault handling code Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 05/12] KVM: x86/mmu: allow APICv memslot to be partially enabled Maxim Levitsky
2021-08-03 9:12 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 06/12] KVM: x86: don't disable APICv memslot when inhibited Maxim Levitsky
2021-08-03 8:44 ` Paolo Bonzini
2021-08-09 18:51 ` Maxim Levitsky
2021-08-09 19:14 ` Sean Christopherson
2021-08-02 18:33 ` [PATCH v3 07/12] KVM: x86: APICv: fix race in kvm_request_apicv_update on SVM Maxim Levitsky
2021-08-02 18:33 ` [PATCH v3 08/12] KVM: SVM: add warning for mistmatch between AVIC state and AVIC access page state Maxim Levitsky
2021-08-03 8:45 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 09/12] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use Maxim Levitsky
2021-08-03 8:47 ` Paolo Bonzini
2021-08-03 9:01 ` Paolo Bonzini [this message]
2021-08-03 9:11 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 10/12] KVM: SVM: remove svm_toggle_avic_for_irq_window Maxim Levitsky
2021-08-03 9:11 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 11/12] KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 12/12] KVM: SVM: AVIC: drop unsupported AVIC base relocation code Maxim Levitsky
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