Re: [PATCH] x86/sev-es: Do not use copy_from_kernel_nofault in early #VC handler

[Peter Zijlstra]

On Fri, Sep 08, 2023 at 07:48:58AM -0700, Dave Hansen wrote:
> On 9/8/23 06:13, Tom Lendacky wrote:
> > On 9/7/23 14:12, Dave Hansen wrote:
> >> But seriously, is it even *possible* to spin up a SEV-SNP VM what
> >> doesn't have NX?
> > 
> > It is a common path, so while an SEV guest would have NX support, you
> > would first have to determine that it is an SEV guest. That would take
> > issuing a CPUID instruction in order to determine if a particular MSR
> > can be read...
> 
> I was thinking more along the lines of telling folks that if they want
> to turn SEV-SNP support on, they also have to give up on running on a
> !NX system.  That would be a _bit_ nicer than just refusing to boot on
> all !NX systems.

I think there were a very limited amount of !NX P4 class x86_64 systems.
I vote in favour of dropping them into the museum bucket, they get to
run an old kernel.

Andrew and me looked at this a few months ago, but I forgot all details
again :/