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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id u8-20020a1709026e0800b0016f1204cde8sm11219119plk.301.2022.08.09.14.38.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Aug 2022 14:38:33 -0700 (PDT) Date: Tue, 9 Aug 2022 21:38:29 +0000 From: Sean Christopherson To: Mathieu Desnoyers Cc: Gavin Shan , shuah , Florian Weimer , kvmarm@lists.cs.columbia.edu, KVM list , linux-kselftest , linux-kernel , Paolo Bonzini , maz , oliver upton , andrew jones , yihyu@redhat.com, shan gavin Subject: Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35 Message-ID: References: <20220809060627.115847-1-gshan@redhat.com> <20220809060627.115847-2-gshan@redhat.com> <8735e6ncxw.fsf@oldenburg.str.redhat.com> <7844e3fa-e49e-de75-e424-e82d3a023dd6@redhat.com> <87o7wtnay6.fsf@oldenburg.str.redhat.com> <616d4de6-81f6-9d14-4e57-4a79fec45690@redhat.com> <797306043.114963.1660047714774.JavaMail.zimbra@efficios.com> <1014177394.115022.1660052656961.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1014177394.115022.1660052656961.JavaMail.zimbra@efficios.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Aug 09, 2022, Mathieu Desnoyers wrote: > ----- On Aug 9, 2022, at 8:21 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote: > > > ----- Gavin Shan wrote: > >> Hi Florian, > >> > >> On 8/9/22 5:16 PM, Florian Weimer wrote: > >> >>> __builtin_thread_pointer doesn't work on all architectures/GCC > >> >>> versions. > >> >>> Is this a problem for selftests? > >> >>> > >> >> > >> >> It's a problem as the test case is running on all architectures. I think I > >> >> need introduce our own __builtin_thread_pointer() for where it's not > >> >> supported: (1) PowerPC (2) x86 without GCC 11 > >> >> > >> >> Please let me know if I still have missed cases where > >> >> __buitin_thread_pointer() isn't supported? > >> > > >> > As far as I know, these are the two outliers that also have rseq > >> > support. The list is a bit longer if we also consider non-rseq > >> > architectures (csky, hppa, ia64, m68k, microblaze, sparc, don't know > >> > about the Linux architectures without glibc support). > >> > > >> > >> For kvm/selftests, there are 3 architectures involved actually. So we > >> just need consider 4 cases: aarch64, x86, s390 and other. For other > >> case, we just use __builtin_thread_pointer() to maintain code's > >> integrity, but it's not called at all. > >> > >> I think kvm/selftest is always relying on glibc if I'm correct. > > > > 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?