[PATCH] KVM: arm64: pkvm: Fixup boot mode to reflect that the kernel resumes from EL1

[Vincent Donnefort]

On Tue, Oct 11, 2022 at 09:58:22PM +0100, Marc Zyngier wrote:
> On Tue, 11 Oct 2022 19:48:39 +0100,
> Oliver Upton <oliver.upton at linux.dev> wrote:
> > 
> > On Tue, Oct 11, 2022 at 05:54:00PM +0100, Marc Zyngier wrote:
> > > The kernel has an awfully complicated boot sequence in order to cope
> > > with the various EL2 configurations, including those that "enhanced"
> > > the architecture. We go from EL2 to EL1, then back to EL2, staying
> > > at EL2 if VHE capable and otherwise go back to EL1.
> > > 
> > > Here's a paracetamol tablet for you.
> > 
> > Heh, still have a bit of a headache from this :)
> > 
> > I'm having a hard time following where we skip the EL2 promotion based
> > on __boot_cpu_mode.
> > 
> > On the cpu_resume() path it looks like we take the return of
> > init_kernel_el() and pass that along to finalise_el2(). As we are in EL1
> > at this point, it seems like we'd go init_kernel_el() -> init_el1().
> > 
> > What am I missing?
> 
> That I'm an idiot.
> 
> This is only necessary on pre-6.0, before 005e12676af0 ("arm64: head:
> record CPU boot mode after enabling the MMU"), as this code-path
> *used* to reload the boot mode from memory. Now, this is directly
> passed as a parameter, making this patch useless.

On a 5.10 though, the suprious HVCs are gone and I have not observed any
regression.

Thanks!

For a stable fix:

Tested-by: Vincent Donnefort <vdonnefort at google.com>

> 
> The joys of looking at too many code bases at the same time... I'll
> see how we can add it to 5.19.
> 
> Thanks,
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.