linux-kernel - [PATCH 0/2] KVM: x86: hyper-v: Conditionally allow SynIC with APICv/AVIC

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Date:   Thu, 13 May 2021 13:37:08 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Kechen Lu <kechenl@...dia.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] KVM: x86: hyper-v: Conditionally allow SynIC with APICv/AVIC

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.

The feature can be tested with QEMU's 'hv-passthrough' debug mode.

Note, 'avic' kvm-amd module parameter is '0' by default and thus needs to
be explicitly enabled.

Vitaly Kuznetsov (2):
  KVM: x86: Invert APICv/AVIC enablement check
  KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in
    use

 arch/x86/include/asm/kvm_host.h |  5 ++++-
 arch/x86/kvm/hyperv.c           | 27 +++++++++++++++++++++------
 arch/x86/kvm/svm/svm.c          |  7 ++++++-
 arch/x86/kvm/vmx/vmx.c          |  7 ++++++-
 arch/x86/kvm/x86.c              |  6 +++---
 5 files changed, 40 insertions(+), 12 deletions(-)

-- 
2.31.1