KVM: Don't enable hardware after a restart/shutdown is initiated
Reject hardware enabling, i.e. VM creation, if a restart/shutdown has been initiated to avoid re-enabling hardware between kvm_reboot() and machine_{halt,power_off,restart}(). The restart case is especially problematic (for x86) as enabling VMX (or clearing GIF in KVM_RUN on SVM) blocks INIT, which results in the restart/reboot hanging as BIOS is unable to wake and rendezvous with APs. Note, this bug, and the original issue that motivated the addition of kvm_reboot(), is effectively limited to a forced reboot, e.g. `reboot -f`. In a "normal" reboot, userspace will gracefully teardown userspace before triggering the kernel reboot (modulo bugs, errors, etc), i.e. any process that might do ioctl(KVM_CREATE_VM) is long gone. Fixes: 8e1c1815 ("KVM: VMX: Disable VMX when system shutdown") Signed-off-by: NSean Christopherson <seanjc@google.com> Acked-by: NMarc Zyngier <maz@kernel.org> Message-Id: <20230512233127.804012-3-seanjc@google.com> Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
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