linux-kernel - Re: [PATCH] KVM: x86: do not shadow apic global definition

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Date:   Tue, 2 Aug 2022 20:12:48 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: do not shadow apic global definition

On Sat, Jul 30, 2022, Vincent MAILHOL wrote:
> On Sat. 30 Jul. 2022 at 02:48, Sean Christopherson <seanjc@...gle.com> wrote:
> > On Fri, Jul 29, 2022, Vincent Mailhol wrote:
> > > arch/x86/include/asm/apic.h declares a global variable named `apic'.
> > >
> > > Many function arguments from arch/x86/kvm/lapic.h also uses the same
> > > name and thus shadow the global declaration. For each case of
> > > shadowing, rename the function argument from `apic' to `lapic'.
> > >
> > > This patch silences below -Wshadow warnings:
> >
> > This is just the tip of the iceberg, nearly every KVM x86 .c file has at least one
> > "apic" variable.  arch/x86/kvm/lapic.c alone has nearly 100.  If this were the very
> > last step before a kernel-wide (or even KVM-wide) enabling of -Wshadow then maybe
> > it would be worth doing, but as it stands IMO it's unnecesary churn.
> 
> I would say the opposite: in terms of *volume*, warnings from apic.c
> would be the tip of the iceberg and apic.h is the submerged part.
> 
> When the warning occurs in a header from the include directory, it
> will spam some random files which include such header. This is
> annoying when trying to triage W=2 warnings because you get totally
> unrelated warning (and W=2 has some useful flags such as
> -Wmaybe-uninitialized so there are some insensitive to check it).
> 
> My intent is only to silence the headers. I do not really care about
> the -Wshadow on *.c files because it is local.

But lapic.h is a KVM-internal header, if you only care about reducing the number
of warnings and not actually "fixing" KVM, then why not suppress or filter the
warnings when building KVM?