linux-kernel - Re: [PATCH] KVM: arm64: Cleanup the __get_fault_info() to take out the code that validates HPFAR

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Message-ID: <86zgel6rz8.wl-maz@kernel.org>
Date:   Tue, 27 Sep 2022 06:18:03 -0400
From:   Marc Zyngier <maz@...nel.org>
To:     Mingwei Zhang <mizhang@...gle.com>,
        Oliver Upton <oliver.upton@...ux.dev>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: arm64: Cleanup the __get_fault_info() to take out the code that validates HPFAR

On Tue, 27 Sep 2022 01:14:16 -0400,
Oliver Upton <oliver.upton@...ux.dev> wrote:
> 
> Hi Mingwei,
> 
> On Tue, Sep 27, 2022 at 12:27:15AM +0000, Mingwei Zhang wrote:
> > Cleanup __get_fault_info() to take out the code that checks HPFAR. The
> > conditions in __get_fault_info() that checks if HPFAR contains a valid IPA
> > is slightly messy in that several conditions are written within one IF
> > statement acrossing multiple lines and are connected with different logical
> > operators. Among them, some conditions come from ARM Spec, while others
> 						   ^~~~~~~~
> 
> Call it the ARM ARM or Arm ARM, depending on what stylization you
> subscribe to :)
> 
> > come from CPU erratum. This makes the code hard to read and
> > difficult to extend.
> 
> I'd recommend you avoid alluding to future changes unless they're posted
> on the mailing list.

Honestly, I'd refrain from such changes *unless* they enable something
else. The current code is well understood by people hacking on it, and
although I don't mind revamping it, it has to be for a good reason.

I'd be much more receptive to such a change if it was a prefix to
something that actually made a significant change.

Thanks,

	M.

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