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    Subject[PATCH 5.11 103/601] KVM: SVM: Do not allow SEV/SEV-ES initialization after vCPUs are created
    Date
    From: Sean Christopherson <seanjc@google.com>

    commit 8727906fde6ea665b52e68ddc58833772537f40a upstream.

    Reject KVM_SEV_INIT and KVM_SEV_ES_INIT if they are attempted after one
    or more vCPUs have been created. KVM assumes a VM is tagged SEV/SEV-ES
    prior to vCPU creation, e.g. init_vmcb() needs to mark the VMCB as SEV
    enabled, and svm_create_vcpu() needs to allocate the VMSA. At best,
    creating vCPUs before SEV/SEV-ES init will lead to unexpected errors
    and/or behavior, and at worst it will crash the host, e.g.
    sev_launch_update_vmsa() will dereference a null svm->vmsa pointer.

    Fixes: 1654efcbc431 ("KVM: SVM: Add KVM_SEV_INIT command")
    Fixes: ad73109ae7ec ("KVM: SVM: Provide support to launch and run an SEV-ES guest")
    Cc: stable@vger.kernel.org
    Cc: Brijesh Singh <brijesh.singh@amd.com>
    Cc: Tom Lendacky <thomas.lendacky@amd.com>
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    Message-Id: <20210331031936.2495277-4-seanjc@google.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kvm/svm/sev.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/arch/x86/kvm/svm/sev.c
    +++ b/arch/x86/kvm/svm/sev.c
    @@ -181,6 +181,9 @@ static int sev_guest_init(struct kvm *kv
    bool es_active = argp->id == KVM_SEV_ES_INIT;
    int asid, ret;

    + if (kvm->created_vcpus)
    + return -EINVAL;
    +
    ret = -EBUSY;
    if (unlikely(sev->active))
    return ret;

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