illumos gate

Unlike VMX, SVM does not restore the TSS when making a round trip to guest context. This means that the TSS must be reloaded "manually" by the OS after vmload/vmrun/vmsave. Although bhyve keeps the GIF cleared while the TSS contains incorrect state, preventing interrupts (including NMI) from triggering it, dtrace probes on any functions called before the TSS is restored will run afoul of the bogus state and likely reboot the machine. This can be seen on an unpatched machine by tracing svm_launch:return, which causes an immediate crash when a VM is running. Like %gsbase, the TSS could be restored before returning from svm_launch(), avoiding those unfortunate crashes.