Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 12 May 2023 16:23:26 -0700
From:   David Matlack <dmatlack@google.com>
To:     Sean Christopherson <seanjc@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Mingwei Zhang <mizhang@google.com>,
        Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH 4/9] KVM: x86/mmu: Rename MMU_WARN_ON() to
 KVM_MMU_WARN_ON()
Message-ID: <ZF7KbsCXBQHnOv7g@google.com>
References: <20230511235917.639770-1-seanjc@google.com>
 <20230511235917.639770-5-seanjc@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230511235917.639770-5-seanjc@google.com>
Precedence: bulk

On Thu, May 11, 2023 at 04:59:12PM -0700, Sean Christopherson wrote:
> Rename MMU_WARN_ON() to make it super obvious that the assertions are
> all about KVM's MMU, not the primary MMU.

I think adding KVM is a step in the right direction but I have 2
remaining problems with KVM_MMU_WARN_ON():

 - Reminds me of VM_WARN_ON(), which toggles between WARN_ON() and
   BUG_ON(), whereas KVM_MMU_WARN_ON() toggles between no-op and
   WARN_ON().

 - It's not obvious from the name that it's a no-op most of the time.

Naming is hard so I might just make things worse by trying but...

How about KVM_MMU_PROVE(condition). That directly pairs it with the new
CONFIG_KVM_PROVE_MMU(), makes it sufficiently different from
VM_WARN_ON() and WARN_ON() that readers will not make assumptions about
what's happening under the hood. Also "PROVE" sounds like a high bar
which conveys this might not always be enabled.

That also will allow us to convert this to a WARN_ON_ONCE() (my
suggestion on the other patch) without having to make the name any
longer.