linux-kernel - [PATCH v2 0/4] KVM: x86: Partially allow KVM_SET_CPUID{,2} after KVM

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Date:   Mon, 17 Jan 2022 16:05:38 +0100
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>,
        Igor Mammedov <imammedo@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/4] KVM: x86: Partially allow KVM_SET_CPUID{,2} after KVM_RUN for CPU hotplug

Changes since v1:
- Drop the allowlist of items which were allowed to change and just allow
the exact same CPUID data [Sean, Paolo]. Adjust selftest accordingly.
- Drop PATCH1 as the exact same change got merged upstream.

Recently, KVM made it illegal to change CPUID after KVM_RUN but
unfortunately this change is not fully compatible with existing VMMs.
In particular, QEMU reuses vCPU fds for CPU hotplug after unplug and it
calls KVM_SET_CPUID2. Relax the requirement by implementing an allowing
KVM_SET_CPUID{,2} with the exact same data.

Vitaly Kuznetsov (4):
  KVM: x86: Do runtime CPUID update before updating
    vcpu->arch.cpuid_entries
  KVM: x86: Partially allow KVM_SET_CPUID{,2} after KVM_RUN
  KVM: selftests: Rename 'get_cpuid_test' to 'cpuid_test'
  KVM: selftests: Test KVM_SET_CPUID2 after KVM_RUN

 arch/x86/kvm/cpuid.c                          | 67 ++++++++++++++++---
 arch/x86/kvm/x86.c                            | 19 ------
 tools/testing/selftests/kvm/.gitignore        |  2 +-
 tools/testing/selftests/kvm/Makefile          |  4 +-
 .../selftests/kvm/include/x86_64/processor.h  |  7 ++
 .../selftests/kvm/lib/x86_64/processor.c      | 33 +++++++--
 .../x86_64/{get_cpuid_test.c => cpuid_test.c} | 30 +++++++++
 7 files changed, 126 insertions(+), 36 deletions(-)
 rename tools/testing/selftests/kvm/x86_64/{get_cpuid_test.c => cpuid_test.c} (83%)

-- 
2.34.1