KVM: PPC: Book3S HV: Read kvm->arch.emul_smt_mode under kvm->lock
Commit 1e175d2e ("KVM: PPC: Book3S HV: Pack VCORE IDs to access full VCPU ID space", 2018-07-25) added code that uses kvm->arch.emul_smt_mode before any VCPUs are created. However, userspace can change kvm->arch.emul_smt_mode at any time up until the first VCPU is created. Hence it is (theoretically) possible for the check in kvmppc_core_vcpu_create_hv() to race with another userspace thread changing kvm->arch.emul_smt_mode. This fixes it by moving the test that uses kvm->arch.emul_smt_mode into the block where kvm->lock is held. Signed-off-by: NPaul Mackerras <paulus@ozlabs.org>
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