linux-kernel - Re: [PATCH v2 1/7] KVM: selftests: Replace int with uint32

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Date:   Thu, 25 May 2023 09:23:03 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Jinrong Liang <ljr.kernel@...il.com>
Cc:     Like Xu <like.xu.linux@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>,
        Aaron Lewis <aaronlewis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Jinrong Liang <cloudliang@...cent.com>,
        linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] KVM: selftests: Replace int with uint32_t for nevents

On Thu, Apr 20, 2023, Jinrong Liang wrote:
> From: Jinrong Liang <cloudliang@...cent.com>
> 
> From: Jinrong Liang <cloudliang@...cent.com>
> 
> Defined as type __u32, the nevents field in kvm_pmu_event_filter
> can only accept positive values within a specific range. Therefore,
> replacing int with uint32_t for nevents ensures consistency and
> readability in the code.

Not really.  It fixes one type of inconsistency that is fairly common (userspace
passing an integer count to the kernel), and replaces it with a different type
of inconsistency (signed iterator comparing against an unsigned count).  There's
already one of those in remove_event(), but I'd rather not create more.

Passing an unsigned int to track what *should* be a small-ish, postive integer
can also make it more difficult to detect bugs, e.g. assertions like this won't
work:

	TEST_ASSERT(nevents >= 0);

If this code were being written from scratch then I wouldn't object to using
uint32_t everywhere, but I don't see the point of trying to retroactively change
the code.