Re: [PATCH 2/2] KVM: arm64: Enable S1PIE for nVHE and hVHE

[Marc Zyngier <maz@kernel.org>]

On Fri, 04 Sep 2026 12:48:14 +0100,
Mark Brown <broonie@kernel.org> wrote:
> 
> On Fri, Sep 04, 2026 at 12:29:23PM +0100, Will Deacon wrote:
> > On Fri, Sep 04, 2026 at 11:33:24AM +0100, Mark Brown wrote:
> 
> > > What about pKVM, my understanding was that that is very much an ongoing
> > > concern and uses the nVHE hypervisor?  My expectation was that this
> > > would only ever get used in hVHE configurations when people enable pKVM
> > > on modern hardware, actual nVHE mode was mostly just carried along with
> > > that.
> 
> > pKVM uses hVHE wherever it can nowadays, so I'm fine with only supporting
> > S1PIE on hVHE and VHE configurations if that's easier to maintain. We
> > just need to make sure that the failure mode for nVHE results in the
> > feature being gracefully disabled, rather than e.g. crashing or quietly
> > doing the wrong thing.
> 
> I figure that if we're supporting hVHE it will end up less complicated
> to also enable nVHE, it reduces the potential for having bad or missing
> fallback paths for features downstream of S1POE.  It's not like it's a
> huge extra bit of code and it seems likely to save hassle down the line.

It's not about the code size. it's about the code being *dead*. Nobody
is going to maintain this configuration, because this is a silly one.

KVM with E2H==0 has reached its architectural peak years ago. We're
not adding anything to it anymore, and all new architectural bits
require running with E2H==1.

	M.

-- 
Jazz isn't dead. It just smells funny.