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Fri, 27 Aug 2021 20:06:20 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 87F07383C99; Fri, 27 Aug 2021 20:06:20 -0400 (EDT) Date: Fri, 27 Aug 2021 20:06:20 -0400 (EDT) From: Mathieu Desnoyers To: Sean Christopherson Message-ID: <1054916754.30218.1630109180443.JavaMail.zimbra@efficios.com> In-Reply-To: References: <20210820225002.310652-1-seanjc@google.com> <766990430.21713.1629731934069.JavaMail.zimbra@efficios.com> <282257549.21721.1629732017655.JavaMail.zimbra@efficios.com> <1700758714.29394.1630003332081.JavaMail.zimbra@efficios.com> <339641531.29941.1630091374065.JavaMail.zimbra@efficios.com> Subject: Re: [PATCH v2 4/5] KVM: selftests: Add a test for KVM_RUN+rseq to detect task migration bugs MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_4101 (ZimbraWebClient - FF91 (Linux)/8.8.15_GA_4059) Thread-Topic: selftests: Add a test for KVM_RUN+rseq to detect task migration bugs Thread-Index: eu98ugrRMaO1Ldp5KUn1lSy5MLrp5Q== X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: KVM list , Peter Zijlstra , Catalin Marinas , linux-kernel , Will Deacon , Guo Ren , linux-kselftest , Ben Gardon , shuah , Paul Mackerras , linux-s390 , gor , "Russell King, ARM Linux" , linux-csky , Christian Borntraeger , Ingo Molnar , dvhart , linux-mips , Boqun Feng , paulmck , Heiko Carstens , rostedt , Shakeel Butt , Andy Lutomirski , Thomas Gleixner , Peter Foley , linux-arm-kernel , Thomas Bogendoerfer , Oleg Nesterov , Paolo Bonzini , linuxppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" ----- On Aug 27, 2021, at 7:23 PM, Sean Christopherson seanjc@google.com wrote: > On Fri, Aug 27, 2021, Mathieu Desnoyers wrote: [...] >> Does it reproduce if we randomize the delay to have it picked randomly from 0us >> to 100us (with 1us step) ? It would remove a lot of the needs for arch-specific >> magic delay value. > > My less-than-scientific testing shows that it can reproduce at delays up to > ~500us, > but above ~10us the reproducibility starts to drop. The bug still reproduces > reliably, it just takes more iterations, and obviously the test runs a bit > slower. > > Any objection to using a 1-10us delay, e.g. a simple usleep((i % 10) + 1)? Works for me, thanks! Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com