linux-kernel - Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested

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Date: Thu, 25 Apr 2024 09:25:58 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Oliver Upton <oliver.upton@...ux.dev>
Cc: Andrew Jones <ajones@...tanamicro.com>, Markus Elfring <Markus.Elfring@....de>, 
	Kunwu Chan <chentao@...inos.cn>, linux-kselftest@...r.kernel.org, kvm@...r.kernel.org, 
	kernel-janitors@...r.kernel.org, 
	Muhammad Usama Anjum <usama.anjum@...labora.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Kunwu Chan <kunwu.chan@...mail.com>, Anup Patel <anup@...infault.org>, 
	Thomas Huth <thuth@...hat.com>
Subject: Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

On Wed, Apr 24, 2024, Oliver Upton wrote:
> Hey,
> 
> On Wed, Apr 24, 2024 at 07:51:44AM -0700, Sean Christopherson wrote:
> > On Wed, Apr 24, 2024, Andrew Jones wrote:
> > > On Tue, Apr 23, 2024 at 12:15:47PM -0700, Sean Christopherson wrote:
> > > ...
> > > > I almost wonder if we should just pick a prefix that's less obviously connected
> > > > to KVM and/or selftests, but unique and short.
> > > >
> > > 
> > > How about kvmsft_ ? It's based on the ksft_ prefix of kselftest.h. Maybe
> > > it's too close to ksft though and would be confusing when using both in
> > > the same test?
> > 
> > I would prefer something short, and for whatever reason I have a mental block
> > with ksft.  I always read it as "k soft", which is completely nonsensical :-)
> 
> I despise brevity in tests, so my strong preference is to use some form
> of 'namespaced' helper. Perhaps others have better memory than
> I do, but I'm quick to forget the selftests library and find the more
> verbose / obvious function names helpful for jogging my memory.

Hmm, I generally agree, but in this case I think there's value in having the
names *not* stand out, because they really are uninteresting and would ideally
blend in.  I can't envision a scenario where we don't want to assert on an OOM,
i.e. there should never be a need to use a raw malloc(), and so I don't see much
value in making it obvious that the call sites are doing something special.

> > > I'm not a huge fan of capital letters, but we could also do something like
> > > MALLOC()/CALLOC().
> > 
> > Hmm, I'm not usually a fan either, but that could actually work quite well in this
> > case.  It would be quite intuitive, easy to visually parse whereas tmalloc() vs
> > malloc() kinda looks like a typo, and would more clearly communicate that they're
> > macros.
> 
> Ooo, don't leave me out on the bikeshedding! How about TEST_MALLOC() /
> TEST_CALLOC(). It is vaguely similar to TEST_ASSERT(), which I'd hope
> would give the impression that an assertion is lurking below.

Yeah, but it could also give the false impression that the macro does something
fancier, e.g. this makes me want to peek at TEST_MALLOC() to see what it's doing

	cpuid = TEST_MALLOC(kvm_cpuid2_size(nr_entries));

whereas this isn't quite enough to pique my curiosity.

	cpuid = MALLOC(kvm_cpuid2_size(nr_entries));

So I have a slight preference for just MALLOC()/CALLOC(), but I'm also ok with a
TEST_ prefix, my brain can adapt.  One of those two flavors has my vote.