Re: [PATCH v4 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor

[Radim KrÄmÃÅ]

2017-07-11 15:38-0400, Bandan Das:
> Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx> writes:
> 
> > 2017-07-11 14:35-0400, Bandan Das:
> >> Jim Mattson <jmattson@xxxxxxxxxx> writes:
> >> ...
> >> >>> I can find the definition for an vmexit in case of index >=
> >> >>> VMFUNC_EPTP_ENTRIES, but not for !vmcs12->eptp_list_address in the SDM.
> >> >>>
> >> >>> Can you give me a hint?
> >> >>
> >> >> I don't think there is. Since, we are basically emulating eptp switching
> >> >> for L2, this is a good check to have.
> >> >
> >> > There is nothing wrong with a hypervisor using physical page 0 for
> >> > whatever purpose it likes, including an EPTP list.
> >> 
> >> Right, but of all the things, a l1 hypervisor wanting page 0 for a eptp list
> >> address most likely means it forgot to initialize it. Whatever damage it does will
> >> still end up with vmfunc vmexit anyway.
> >
> > Most likely, but not certainly.  I also don't see a to diverge from the
> > spec here.
> 
> Actually, this is a specific case where I would like to diverge from the spec.
> But then again, it's L1 shooting itself in the foot and this would be a rarely
> used code path, so, I am fine removing it.

Thanks, we're not here to judge the guest, but to provide a bare-metal
experience. :)