From: Maxim Levitsky <mlevitsk@redhat.com>
To: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org (open list:X86 ARCHITECTURE (32-BIT
AND 64-BIT)), Jim Mattson <jmattson@google.com>,
Joerg Roedel <joro@8bytes.org>, Borislav Petkov <bp@alien8.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
Sean Christopherson <seanjc@google.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Subject: [PATCH v2 8/8] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use
Date: Tue, 13 Jul 2021 17:20:23 +0300 [thread overview]
Message-ID: <20210713142023.106183-9-mlevitsk@redhat.com> (raw)
In-Reply-To: <20210713142023.106183-1-mlevitsk@redhat.com>
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: in case APICv/AVIC usage is impossible, AutoEOI
is still preferred.
Maxim:
- added SRCU lock drop around call to kvm_request_apicv_update
- 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 | 34 +++++++++++++++++++++++++++------
2 files changed, 31 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e11d64aa0bcd..f900dca58af8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -956,6 +956,9 @@ 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..6bf47a583d0e 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -85,9 +85,22 @@ static bool synic_has_vector_auto_eoi(struct kvm_vcpu_hv_synic *synic,
return false;
}
+
+static void synic_toggle_avic(struct kvm_vcpu *vcpu, bool activate)
+{
+ srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
+ kvm_request_apicv_update(vcpu->kvm, activate,
+ APICV_INHIBIT_REASON_HYPERV);
+ vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+}
+
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 +109,23 @@ 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)
+ synic_toggle_avic(vcpu, false);
+ } else if (!auto_eoi_new && auto_eoi_old) {
+ if (atomic_dec_return(&hv->synic_auto_eoi_used) == 0)
+ synic_toggle_avic(vcpu, true);
+ }
}
static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
@@ -933,12 +959,6 @@ 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 +2486,8 @@ 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
next prev parent reply other threads:[~2021-07-13 14:21 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-13 14:20 [PATCH v2 0/8] My AVIC patch queue Maxim Levitsky
2021-07-13 14:20 ` [PATCH v2 1/8] KVM: SVM: svm_set_vintr don't warn if AVIC is active but is about to be deactivated Maxim Levitsky
2021-07-13 14:20 ` [PATCH v2 2/8] KVM: SVM: tweak warning about enabled AVIC on nested entry Maxim Levitsky
2021-07-13 14:20 ` [PATCH v2 3/8] KVM: SVM: use vmcb01 in svm_refresh_apicv_exec_ctrl Maxim Levitsky
2021-07-13 14:20 ` [PATCH v2 4/8] KVM: x86: APICv: drop immediate APICv disablement on current vCPU Maxim Levitsky
2021-07-13 14:20 ` [PATCH v2 5/8] KVM: x86: APICv: fix race in kvm_request_apicv_update on SVM Maxim Levitsky
2021-07-26 22:34 ` Paolo Bonzini
2021-07-27 13:22 ` Maxim Levitsky
2021-07-13 14:20 ` [PATCH v2 6/8] KVM: SVM: add warning for mistmatch between AVIC state and AVIC access page state Maxim Levitsky
2021-07-13 14:20 ` [PATCH v2 7/8] KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC Maxim Levitsky
2021-07-13 14:20 ` Maxim Levitsky [this message]
2021-07-18 12:13 ` [PATCH v2 8/8] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use Maxim Levitsky
2021-07-19 7:47 ` Vitaly Kuznetsov
2021-07-19 9:00 ` Maxim Levitsky
2021-07-19 9:23 ` Vitaly Kuznetsov
2021-07-19 9:58 ` Maxim Levitsky
2021-07-19 18:49 ` Sean Christopherson
2021-07-20 9:40 ` Maxim Levitsky
2021-07-22 9:12 ` KVM's support for non default APIC base Maxim Levitsky
2021-08-02 9:20 ` Maxim Levitsky
2021-08-06 21:55 ` Sean Christopherson
2021-08-09 9:40 ` Maxim Levitsky
2021-08-09 15:57 ` Sean Christopherson
2021-08-09 16:47 ` Jim Mattson
2021-08-10 20:42 ` Maxim Levitsky
2021-07-22 17:35 ` [PATCH v2 8/8] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use Maxim Levitsky
2021-07-22 19:06 ` Sean Christopherson
2021-07-27 13:05 ` Maxim Levitsky
2021-07-27 17:48 ` Ben Gardon
2021-07-27 18:17 ` Sean Christopherson
2021-07-29 14:10 ` Maxim Levitsky
2021-07-26 17:24 ` [PATCH v2 0/8] My AVIC patch queue Paolo Bonzini
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