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Reply-To: Gavin Shan <gshan@redhat.com>
Subject: Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Sean Christopherson <seanjc@google.com>
Cc:     shuah <shuah@kernel.org>, Florian Weimer <fweimer@redhat.com>,
        kvmarm <kvmarm@lists.cs.columbia.edu>,
        KVM list <kvm@vger.kernel.org>,
        linux-kselftest <linux-kselftest@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>, maz <maz@kernel.org>,
        oliver upton <oliver.upton@linux.dev>,
        andrew jones <andrew.jones@linux.dev>,
        yihyu <yihyu@redhat.com>, shan gavin <shan.gavin@gmail.com>
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From:   Gavin Shan <gshan@redhat.com>
Message-ID: <1191ef05-ef2c-fe8e-656d-cb89141b36fb@redhat.com>
Date:   Thu, 11 Aug 2022 09:52:55 +1000
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Hi Mathieu,

On 8/10/22 10:13 PM, Mathieu Desnoyers wrote:
> ----- On Aug 9, 2022, at 5:38 PM, Sean Christopherson seanjc@google.com wrote: 
>> On Tue, Aug 09, 2022, Mathieu Desnoyers wrote:
>>> ----- On Aug 9, 2022, at 8:21 AM, Mathieu Desnoyers
>>> mathieu.desnoyers@efficios.com wrote:

[...]

>>>>
>>>> All those are handled in the rseq selftests and in librseq. Why duplicate all
>>>> that logic again?
>>>
>>> More to the point, considering that we have all the relevant rseq registration
>>> code in tools/testing/selftests/rseq/rseq.c already, and the relevant thread
>>> pointer getter code in tools/testing/selftests/rseq/rseq-*thread-pointer.h,
>>> is there an easy way to get test applications in tools/testing/selftests/kvm
>>> and in tools/testing/selftests/rseq to share that common code ?
>>>
>>> Keeping duplicated compatibility code is bad for long-term maintainability.
>>
>> Any reason not to simply add tools/lib/rseq.c and then expose a helper to get
>> the
>> registered rseq struct?
> 
> Indeed, moving rseq.c to tools/lib/ would allow building a .so from any selftest
> which needs to use it.
> 
> And we could move the relevant rseq helper header files to tools/include/rseq/*
> as well.
> 
> Thoughts ?
> 

One question is how librseq.so can be built automatically, when I'm going to
build tools/testing/selftests/kvm/rseq_test.

     # cd linux/tools/testing/selftests/kvm
     # make rseq_test

It's not perfect if I have to build tools/lib/librseq.so in advance, in order
to build tools/testing/selftests/kvm/rseq_test for the sake of dependency.

Thanks,
Gavin