Re: [PATCH 1/2] KVM: arm64: Initialize HCR_EL2.E2H early

[Mark Rutland <mark.rutland@arm.com>]

On Fri, Feb 28, 2025 at 09:43:20AM +0000, Marc Zyngier wrote:
> On Fri, 28 Feb 2025 09:29:55 +0000,
> Leo Yan <leo.yan@arm.com> wrote:
> > 
> > Hi Mark,
> > 
> > On Thu, Feb 27, 2025 at 06:05:25PM +0000, Mark Rutland wrote:
> > 
> > [...]
> > 
> > > +.macro init_el2_hcr	val
> > > +	mov_q	x0, \val
> > > +
> > > +	/*
> > > +	 * Compliant CPUs advertise their VHE-onlyness with
> > > +	 * ID_AA64MMFR4_EL1.E2H0 < 0. On such CPUs HCR_EL2.E2H is RES1, but it
> > > +	 * can reset into an UNKNOWN state and might not read as 1 until it has
> > > +	 * been initialized explicitly.
> > 
> > For ID_AA64MMFR4_EL1.E2H0 < 0 case, the code actually clears the
> > HCR_EL2.E2H bit.
> >
> > Hence, the comment should be corrected as: "... it can reset into an
> > UNKNOWN state and might not read as 0 until it has been initialized
> > explicitly".
> 
> The comment is just fine. It is the code that is wrong, as it avoids
> setting E2H when E2H0 < 0 while we want the exact opposite behaviour.
> 
> As a result, 'b.lt' really should be a 'b.ge'. Or the original code
> kept as is.

Ugh, yes. I got confused and got the condition backwards.

Either works. Using 'b.ge' is closer to my intention -- I found the
'tbz' of the sign bit somewhat surprising and that needed a longer line
after the lable name changed.

Would you like me to respin, or would you be hapy to fix up when
applying?

Mark.