Re: [RFC PATCH 3/5] x86/kexec: Disable kexec/kdump on platforms with TDX partial write erratum

[Edgecombe, Rick P]

On Thu, 2025-03-13 at 00:57 +0000, Huang, Kai wrote:
> > Continuing an internal discussion... A problem with the plan to more simply
> > start support for kexec by not supporting the errata platforms is that when
> > these platforms configure TDX they will lose kexec by default.
> > 
> > Probably a better default for a lot of kernels would be to have kexec work
> > by
> > default, and require opt-in to use TDX (and lose kexec). One idea was a
> > kernel
> > parameter be required to enable TDX on those platforms. But then we are
> > starting
> > to add complexity to avoid other complexity (the errata platform kexec
> > support).
> > 
> > Still, it may be a net win on complexity.
> 
> We can add a kernel parameter 'tdx_host={on|off}' and skip all TDX code (thus
> no
> erratum detection) when it is off.  I suppose it will be useful in general
> anyway even w/o the context of kexec.

What exactly are you thinking? Add a tdx_host parameter, but what is the default
behavior? When tdx_host=on with the errata, kexec must still be disabled, right?
Better to return an error, than proceed and crash.