Re: [PATCH 00/15] KVM: arm64: Debug cleanups

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

On Sat, Nov 09, 2024 at 01:13:06PM +0000, Marc Zyngier wrote:
> On Fri, 08 Nov 2024 22:24:04 +0000,
> Oliver Upton <oliver.upton@linux.dev> wrote:
> > 
> > The debug code has become a bit difficult to reason about, especially
> > all the hacks and bandaids for state tracking + trap configuration.
> > 
> > This series reworks the entire mess around using a single enumeration to
> > track the state of the debug registers (free, guest-owned, host-owned),
> > using that to drive trap configuration and save/restore.
> > 
> > On top of that, this series wires most of the implementation into vCPU
> > load/put rather than the main KVM_RUN loop. This has been a long time
> > coming for VHE, as a lot of the trap configuration and EL1 state gets
> > loaded into hardware at that point anyway.
> > 
> > The save/restore of the debug registers is simplified quite a bit as
> > well. KVM will now restore the registers for *any* access rather than
> > just writes, and keep doing so until the next vcpu_put() instead of
> > dropping it on the floor after the next exception.
> 
> Overall, I really like the shape of this. It is a great bit a
> refactoring, and while I left a few comments on the bits that I think
> can be improved, it is already a good candidate for 6.14.
> 
> My only gripe is that it drops a fair bit of "documentation" without
> replacing it with something more current. Given the more "distributed"
> nature of the new code, having some sort of high-level description of
> the handling flow in debug.c would very much help (even it the outcome
> is a less impressive diffstat ;-).

Thanks for reviewing it. I should've made mention about it in the cover
letter, but I dumped a lot of the existing documentation because I found
it to be rambly and actually make things _less_ clear.

But I agree, a centralized description of what's going on would be
useful.

-- 
Thanks,
Oliver