Re: [PATCH v3 40/75] x86/sev-es: Compile early handler code into kernel image

Joerg Roedel
2020-06-11T10:05:19Z

On Thu, Jun 04, 2020 at 05:19:53PM +0200, Borislav Petkov wrote:
> On Thu, Jun 04, 2020 at 01:54:13PM +0200, Joerg Roedel wrote:
> > It is not only the trace-point, this would also eliminate exception
> > handling in case the MSR access triggers a #GP. The "Unhandled MSR
> > read/write" messages would turn into a "General Protection Fault"
> > message.
>
> But the early ones can trigger a #GP too. And there we can't handle
> those #GPs.
>
> Why would the late ones need exception handling all of a sudden? And
> for the GHCB MSR, of all MSRs which the SEV-ES guest has used so far to
> bootstrap?!

For example when there is a bug in the code which triggers an SEV-ES-only
code-path at runtime on bare-metal or in a non-SEV-ES VM. When the MSR
is accessed accidentially in that code-path the exception handling will
be helpful.

Joerg