Re: [PATCH 08/16] KVM: x86/mmu: Bug the VM if kvm_zap_gfn_range() is called for TDX

[Huang, Kai]

On 17/05/2024 9:46 am, Edgecombe, Rick P wrote:
> On Tue, 2024-05-14 at 17:59 -0700, Rick Edgecombe wrote:
> > For lack of a better method currently, use kvm_gfn_shared_mask() to
> > determine if private memory cannot be zapped (as in TDX, the only VM type
> > that sets it).
>
> Trying to replace kvm_gfn_shared_mask() with something appropriate, I saw that
> SNP actually uses this function:
> https://lore.kernel.org/kvm/20240501085210.2213060-12-michael.roth@xxxxxxx/
>
> So trying to have a helper that says "The VM can't zap and refault in memory at
> will" won't cut it. I guess there would have to be some more specific. I'm
> thinking to just drop this patch instead.

Or KVM_BUG_ON() in the callers by explicitly checking VM type being TDX 
as I mentioned before.

Having such checking in a generic function like this is just dangerous 
and not flexible.

Just my 2 cents, though.