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 11:11:13 +0200 [thread overview]
Message-ID: <eb012e5e-e116-98e9-ef77-8690be66b06c@redhat.com> (raw)
In-Reply-To: <20210802183329.2309921-10-mlevitsk@redhat.com>
On 02/08/21 20:33, Maxim Levitsky wrote:
> + 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);
Hmm no, Reviewed-by rescinded. This is racy, you cannot use atomics.
The check for zero needs to happen within the lock.
The easiest way is to have a __kvm_request_apicv_update function that
leaves it to the caller to take the lock. Then synic_update_vector can do
if (!!auto_eoi_old == !!auto_eoi_new)
return;
mutex_lock(&kvm->apicv_update_lock);
bool was_active = hv->synic_auto_eoi_used;
if (auto_eoi_new)
hv->synic_auto_eoi_used++;
else
hv->synic_auto_eoi_used--;
if (!!hv->synic_auto_eoi_used != !!was_active)
__kvm_request_apicv_update(vcpu->kvm,
!!hv->synic_auto_eoi_used,
APICV_INHIBIT_REASON_HYPERV);
mutex_unlock(&kvm->apicv_update_lock);
Please add a note to synic_auto_eoi_used that it is protected by
apicv_update_lock.
Thanks,
Paolo
next prev parent reply other threads:[~2021-08-03 9:11 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
2021-08-03 9:11 ` Paolo Bonzini [this message]
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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