On Fri, Nov 09, 2018 at 11:04:59AM -0700, Rian Quinn wrote: > >> I apologize upfront if this is the wrong place to post this, pretty new to > >> this. > >> > >> We are working on the Bareflank Hypervisor (www.bareflank.org), and we > >> are passing through the INIT/SIPI process (similar to how a VMX > >> rootkit from EFI might boot the OS) and we noticed that on Arch Linux, > >> the INIT/SIPI process stalls, something we are not seeing on Ubuntu. > > > > I'm confused, INIT is blocked post-VMXON, what are you passing through? > > You are correct that INIT will track unconditionally, but all we do is set the > activity state to wait-for-sipi and return back, allowing Linux to continue > its boot process.
That's not pass-through, maybe call it reflection? I realize I'm being a bit pedantic, but differentiating between the two matters since true pass-through gives you bare metal performance whereas reflection obviously requires a round-trip VMX transition. Most hypervisors don't need a delay because they don't pass-through the local APIC and instead emulate INIT/SIPI/SIPI. In other words, forcing a delay for all hypervisors is unwarranted. The correct fix is probably to add a new hook to struct x86_hyper_init to provide a custom init delay, and add Bareflank as a new hypervisor.