From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Maxim Levitsky <mlevitsk@redhat.com>,
Kechen Lu <kechenl@nvidia.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH v2 5/5] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use
Date: Tue, 18 May 2021 16:43:39 +0200 [thread overview]
Message-ID: <20210518144339.1987982-6-vkuznets@redhat.com> (raw)
In-Reply-To: <20210518144339.1987982-1-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: in case APICv/AVIC usage is impossible, AutoEOI
is still preferred.
Signed-off-by: Vitaly Kuznetsov <vkuznets@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 bf5807d35339..5e03ab4c0e4f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -936,6 +936,9 @@ 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 f98370a39936..89e7d5b99279 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -87,6 +87,10 @@ 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;
@@ -95,10 +99,25 @@ 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,
@@ -931,12 +950,6 @@ 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;
@@ -2198,6 +2211,8 @@ 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;
+ if (enable_apicv)
+ ent->eax |= HV_DEPRECATING_AEOI_RECOMMENDED;
/*
* Default number of spinlock retry attempts, matches
* HyperV 2016.
--
2.31.1
next prev parent reply other threads:[~2021-05-18 14:44 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-18 14:43 [PATCH v2 0/5] KVM: x86: hyper-v: Conditionally allow SynIC with APICv/AVIC Vitaly Kuznetsov
2021-05-18 14:43 ` [PATCH v2 1/5] KVM: SVM: Drop unneeded CONFIG_X86_LOCAL_APIC check for AVIC Vitaly Kuznetsov
2021-05-18 19:57 ` Sean Christopherson
2021-05-26 9:54 ` Maxim Levitsky
2021-05-18 14:43 ` [PATCH v2 2/5] KVM: VMX: Drop unneeded CONFIG_X86_LOCAL_APIC check from cpu_has_vmx_posted_intr() Vitaly Kuznetsov
2021-05-18 19:57 ` Sean Christopherson
2021-05-26 9:54 ` Maxim Levitsky
2021-05-18 14:43 ` [PATCH v2 3/5] KVM: x86: Use common 'enable_apicv' variable for both APICv and AVIC Vitaly Kuznetsov
2021-05-18 20:39 ` Sean Christopherson
2021-05-19 7:58 ` Vitaly Kuznetsov
2021-05-24 16:18 ` Paolo Bonzini
2021-05-24 16:52 ` Sean Christopherson
2021-05-24 17:02 ` Paolo Bonzini
2021-05-26 9:56 ` Maxim Levitsky
2021-05-26 15:07 ` Sean Christopherson
2021-05-26 15:52 ` Maxim Levitsky
2021-05-27 11:39 ` Paolo Bonzini
2021-05-18 14:43 ` [PATCH v2 4/5] KVM: x86: Invert APICv/AVIC enablement check Vitaly Kuznetsov
2021-05-18 21:05 ` Sean Christopherson
2021-05-26 9:57 ` Maxim Levitsky
2021-05-26 10:40 ` Vitaly Kuznetsov
2021-05-26 11:11 ` Maxim Levitsky
2021-05-18 14:43 ` Vitaly Kuznetsov [this message]
2021-05-24 16:21 ` [PATCH v2 5/5] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use Paolo Bonzini
2021-05-25 6:23 ` Vitaly Kuznetsov
2021-05-25 7:11 ` Paolo Bonzini
2021-05-26 10:02 ` Maxim Levitsky
2021-05-26 10:01 ` Maxim Levitsky
2021-05-26 9:54 ` [PATCH v2 0/5] KVM: x86: hyper-v: Conditionally allow SynIC with APICv/AVIC Maxim Levitsky
2021-05-27 8:35 ` Vitaly Kuznetsov
2021-05-27 15:49 ` Maxim Levitsky
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