Re: [RFC PATCH v5 04/45] KVM: x86: Make "external SPTE" ops that can fail RET0 static calls

[Sean Christopherson]

On Fri, Jan 30, 2026, Rick P Edgecombe wrote:
> On Thu, 2026-01-29 at 17:28 -0800, Sean Christopherson wrote:
> > 
> > Hmm, that's probably doable, but definitely in a separate patch. 
> > E.g. something
> > like:
> 
> I think it would be a good change. But after more consideration, I
> think the original patch is good on its own. Better to turn a bug into
> a deterministic thing, than an opportunity to consume stack. Seems to
> be what you intended.
> 
> Another idea would be to have a variant that returns an error instead
> of 0 so the callers can have there error logic triggered, but it's all
> incremental value on top of this.

I don't like that idea, at all.  First and foremost, I don't want to litter KVM
with WARNs for things that simply can't happen.  I'm fine adding infrastructure
that hides the sanity checks, but I don't want to bleed that into callers.

The other aspect I dislike is that returning a specific errno could lead to all
sorts of weirdness and hidden dependencies.

All in all, I think we'd be increasing the chances of creating bugs just to harden
against issues that in all likelihood will never happen.