Re: [PATCH 2/2] KVM: arm64: Fix vcpu_{read,write}_sys_reg() accessors

[Oliver Upton <oliver.upton@linux.dev>]

On Thu, Aug 14, 2025 at 05:16:57PM +0100, Marc Zyngier wrote:
> My current conclusion is that a macro hack is not really practical, if
> only because we end-up here from out-of-line C code, and that at this
> stage we've lost all symbolic information.
> 
> We *could* take the nuclear option of re-modelling the sysreg enum as
> a bunch of #define, similar to the way we deal with vcpu flags, and
> have accessors for the various bits of information, but that comes
> with two different problems:
> 
> - we don't have a good way to iterate over symbolic registers
> 
> - we need to repaint a large portion of the code base
> 
> Given that, I've taken another approach, which is to move all these
> things close together (no more inlining), and add enough WARN_ON()s
> that you really have to try and game the code to miss something and
> not get caught. In the process, I found a couple of extra stragglers
> that are always loaded when running a 32bit guest (the *32_EL2
> registers...).
> 
> I've pushed the current state on my kvm-arm64/at-fixes-6.17 branch,
> and I'll try to repost patches over the weekend.

Thanks! I've taken a glance at the branch and LGTM. Just wanted to make
sure we have sufficient idiotproofing for the next time I misuse this
stuff ;-)

Best,
Oliver