On Mon, Feb 8, 2021 at 9:11 AM Sean Christopherson <[email protected]> wrote: > > On Sun, Feb 07, 2021, Andy Lutomirski wrote: > >
> > How much of the register state is revealed to the VMM when we do a TDVMCALL? > > Presumably we should fully sanitize all register state that shows up in > > cleartext on the other end, and we should treat all regs that can be > > modified > > by the VMM as clobbered. > > The guest gets to choose, with a few restrictions. RSP cannot be exposed to > the > host. RAX, RCX, R10, and R11 are always exposed as they hold mandatory info > about the TDVMCALL (TDCALL fn, GPR mask, GHCI vs. vendor, and TDVMCALL fn). > All > other GPRs are exposed and clobbered if their bit in RCX is set, otherwise > they > are saved/restored by the TDX-Module. > > I agree with Dave, pass everything required by the GHCI in the main routine, > and > sanitize and save/restore all such GPRs. Sounds okay to me.
