linux-kernel - Re: [PATCH v7 4/5] KVM: selftests: Add atoi_positive() and atoi_non

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Message-ID: <Y2FxgNCw11tA7yDz@google.com>
Date:   Tue, 1 Nov 2022 19:20:32 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     pbonzini@...hat.com, dmatlack@...gle.com, andrew.jones@...ux.dev,
        wei.w.wang@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 4/5] KVM: selftests: Add atoi_positive() and
 atoi_non_negative() for input validation

On Tue, Nov 01, 2022, Vipin Sharma wrote:
> On Mon, Oct 31, 2022 at 12:48 PM Sean Christopherson <seanjc@...gle.com> wrote:
> >
> > On Mon, Oct 31, 2022, Vipin Sharma wrote:
> > > diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> > > index ec0f070a6f21..210e98a49a83 100644
> > > --- a/tools/testing/selftests/kvm/lib/test_util.c
> > > +++ b/tools/testing/selftests/kvm/lib/test_util.c
> > > @@ -353,3 +353,19 @@ int atoi_paranoid(const char *num_str)
> > >
> > >       return num;
> > >  }
> > > +
> > > +uint32_t atoi_positive(const char *num_str)
> >
> > I think it makes sense to inline atoi_positive() and atoi_non_negative() in
> > test_util.h.  Depending on developer's setups, it might be one less layer to jump
> > through to look at the implementation.
> >
> 
> I am not sure if this makes life much easier for developers, as
> "inline" can totally be ignored by the compiler. Also, not sure how
> much qualitative improvement it will add in the developer's code
> browsing journey. Anyways, I will add "inline" in the next version.

To be clear, it's not about adding "inline", it's about not having separate
declarations and definitions.  E.g. I've yet to achieve a setup that has 100%
accuracy when it comes to navigating to a definition versus a declaration.  And
when poking around code, seeing a "static inline" function provides a hint that
a function is likely a simple wrapper without even having to look at the
implementation.

These are all small things, but I can't think of a reason _not_ to inline these
trivial wrappers.

> > Last thought: my vote would be to ignore the 80 char soft limit when adding the
> > "name" to these calls, in every case except nr_memslot_modifications the overrun
> > is relatively minor and not worth wrapping.  See below for my thougts on that one.
> >
> > >                       break;
> > >               case 'm':
> > > -                     max_mem = atoi_paranoid(optarg) * size_1gb;
> > > +                     max_mem = atoi_positive(optarg) * size_1gb;
> > >                       TEST_ASSERT(max_mem > 0, "memory size must be >0");
> >
> > This assert can be dropped, max_mem is a uint64_t so wrapping to '0' is impossible.
> >
> 
> I intentionally kept it, as it is also protecting against having
> accidently making size_1gb to 0.

Heh, the test has far, far bigger problems if it screws up size_1gb.  And that's
an orthogonal concern as the test would be horrifically broken regardless of
whether or not the user specified '-m' and/or '-s'.

A better approach is to replace the homebrewed size_1gb with SZ_1G from
tools/include/linux/sizes.h.  I, and many others, completely overlooked size.h.