Re: [PATCH v2 2/5] x86/kexec: do unconditional WBINVD in relocate_kernel()

[Tom Lendacky]

On 3/20/24 15:48, Huang, Kai wrote:
> > > Hi Tom,
> > >
> > > I am not aware of kexec() support status for SEV-ES/SEV-SNP guests. 
> > > Does patch 1 break them?
> >
> > SNP guests can kexec with some patches that are currently in process 
> > around shared to private memory conversions. ES guests can only kexec 
> > with a single vCPU. There was a recent patch series to add support for 
> > multiple vCPUs.
> >
> > Patch #1 doesn't break either ES or SNP because we still have an IDT and 
> > traditional kernel addressing in place, so the #VC can be handled.
>
> How about plain SEV guest?

A plain SEV guest is fine, since WBINVD is intercepted and would just exit 
to the hypervisor (#VC doesn't happen with plain SEV).

Thanks,
Tom

> > Whereas patch #2 has switched to identity mapping and removed the IDT, 
> > so a #VC causes a triple fault.
>
> That makes sense.  Thanks.
>
> Hi Kirill,
>
> Does TDX guest have similar behaviour -- that WBINVD in stop_this_cpu() 
> can be handled although it causes #VE, while WBINVD in relocate_kernel() 
> will just triple fault the guest?