Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) client-ip=2620:137:e000::3:5;
Date:   Tue, 10 Oct 2023 16:46:50 -0700
In-Reply-To: <20231010072359.0df918e9@kernel.org>
Mime-Version: 1.0
References: <20231006205415.3501535-1-kuba@kernel.org> <ZSQ7z8gqIemJQXI6@google.com>
 <20231009110613.2405ff47@kernel.org> <ZSRVoYbCuDXc7aR7@google.com>
 <20231009144944.17c8eba3@kernel.org> <87sf6i6gzh.fsf@intel.com> <20231010072359.0df918e9@kernel.org>
Message-ID: <ZSXiapPMIPj3ko41@google.com>
Subject: Re: [PATCH] KVM: deprecate KVM_WERROR in favor of general WERROR
From:   Sean Christopherson <seanjc@google.com>
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     Jani Nikula <jani.nikula@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        pbonzini@redhat.com, workflows@vger.kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Content-Type: text/plain; charset="us-ascii"
Precedence: bulk

On Tue, Oct 10, 2023, Jakub Kicinski wrote:
> On Tue, 10 Oct 2023 11:04:18 +0300 Jani Nikula wrote:
> > > If you do invest in build testing automation, why can't your automation
> > > count warnings rather than depend on WERROR? I don't understand.  
> > 
> > Because having both CI and the subsystem/driver developers enable a
> > local WERROR actually works in keeping the subsystem/driver clean of
> > warnings.
> > 
> > For i915, we also enable W=1 warnings and kernel-doc -Werror with it,
> > keeping all of them warning clean. I don't much appreciate calling that
> > anti-social.
> 
> Anti-social is not the right word, that's fair.
> 
> Werror makes your life easier while increasing the blast radius 
> of your mistakes. So you're trading off your convenience for risk
> of breakage to others. Note that you can fix issues locally very
> quickly and move on. Others have to wait to get your patches thru
> Linus.
> 
> > >> I disagree.  WERROR simply doesn't provide the same coverage.  E.g. it can't be
> > >> enabled for i386 without tuning FRAME_WARN, which (a) won't be at all obvious to
> > >> the average contributor and (b) increasing FRAME_WARN effectively reduces the
> > >> test coverage of KVM i386.
> > >> 
> > >> For KVM x86, I want the rules for contributing to be clearly documented, and as
> > >> simple as possible.  I don't see a sane way to achieve that with WERROR=y.  
> > 
> > The DRM_I915_WERROR config depends on EXPERT and !COMPILE_TEST, and to
> > my knowledge this has never caused issues outside of i915 developers and
> > CI.
> 
> Ack, I think you do it right. I was trying to establish a precedent
> so that we can delete these as soon as they cause an issue, not sooner.

So isn't the underlying problem simply that KVM_WERROR is enabled by default for
some configurations?  If that's the case, then my proposal to make KVM_WERROR
always off by default, and "depends on KVM && EXPERT && !KASAN", would make this
go away, no?