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

[Marc Zyngier <maz@kernel.org>]

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,

	M.

-- 
Without deviation from the norm, progress is not possible.