From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6C80C25B08 for ; Wed, 10 Aug 2022 12:29:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 809694D8D5; Wed, 10 Aug 2022 08:29:24 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, body has been altered) header.i=@efficios.com Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id oHMIfeZIuM6d; Wed, 10 Aug 2022 08:29:23 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 29F604D8DE; Wed, 10 Aug 2022 08:29:23 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4ABE54D8D5 for ; Wed, 10 Aug 2022 08:29:22 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZNbb7JdxmkRU for ; Wed, 10 Aug 2022 08:29:20 -0400 (EDT) Received: from mail.efficios.com (mail.efficios.com [167.114.26.124]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id B0CD14D8D3 for ; Wed, 10 Aug 2022 08:29:20 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 68B2143EA36; Wed, 10 Aug 2022 08:29:20 -0400 (EDT) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id h3gb2233B6MC; Wed, 10 Aug 2022 08:29:19 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 6CD9E43ED02; Wed, 10 Aug 2022 08:29:19 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 6CD9E43ED02 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1660134559; bh=QBchzkobu6L+jcpw+dUlEz0k3O8E4+6GRlWJ0MXHIvs=; h=Date:From:To:Message-ID:MIME-Version; b=PI+Lh9go6DchA6I6ZfU44MkHtWrACOshp+vTuj5r62mRjexFkHf0bTwM97qiZ/UB3 X+UMSBKCbjhj4tGMCQnyIO2LqeuSeymfaH6LhpEZt8iYn+q/jF/v9aZKRuhorjXNnR KdIyZvvD81ucWRIWTXKs0B+rCjlzsXOSGYyPnMZ7Atx0AWP1t7xbIo1DIng+pAORyl Ae7SiOp0Ot3nfCnUtBJMe3V/u1tuw8BlefFcxJKDUBnq1mg/9xP4/3qpxMPuv2G0X9 mpl2nMqj00hi17podl51qHx2TpsJ/tJuPGhGJS/+somd7WwcN9zHiCLod2ZNGidtDh 8ZR/tYJ9G9qGQ== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 9xQH-mneLfu7; Wed, 10 Aug 2022 08:29:19 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 5327143E933; Wed, 10 Aug 2022 08:29:19 -0400 (EDT) Date: Wed, 10 Aug 2022 08:29:19 -0400 (EDT) From: Mathieu Desnoyers To: Gavin Shan Message-ID: <1316061904.375.1660134559269.JavaMail.zimbra@efficios.com> In-Reply-To: <8c1f33b4-a5a1-fcfa-4521-36253ffa22c8@redhat.com> References: <20220809060627.115847-1-gshan@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> <8c1f33b4-a5a1-fcfa-4521-36253ffa22c8@redhat.com> Subject: Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35 MIME-Version: 1.0 X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_4372 (ZimbraWebClient - FF103 (Linux)/8.8.15_GA_4372) Thread-Topic: selftests: Make rseq compatible with glibc-2.35 Thread-Index: Hmn4zQY3JK/eFlOJPqqhWHevLMt86A== Cc: Florian Weimer , shan gavin , KVM list , linux-kernel , andrew jones , yihyu , linux-kselftest , maz , Paolo Bonzini , shuah , kvmarm X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu ----- On Aug 9, 2022, at 8:37 PM, Gavin Shan gshan@redhat.com wrote: > Hi Mathieu and Sean, > > On 8/10/22 7:38 AM, Sean Christopherson wrote: >> 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: >>>>> 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? >> > > There are couple of reasons, not to share > tools/testing/selftests/rseq/librseq.so > or add tools/lib/librseq.so. Please let me know if the arguments making sense > to you? > > - By design, selftests/rseq and selftests/kvm are parallel. It's going to > introduce > unnecessary dependency for selftests/kvm to use selftests/rseq/librseq.so. To > me, > it makes the maintainability even harder. In terms of build system, yes, selftests/rseq and selftests/kvm are side-by-side, and I agree it is odd to have a cross-dependency. That's where moving rseq.c to tools/lib/ makes sense. > > - What selftests/kvm needs is rseq-thread-pointer.h, which accounts for ~5% of > functionalities, provided by selftests/rseq/librseq.so. I've never seen this type of argument used to prevent using a library before, except on extremely memory-constrained devices, which is not our target here. Even if you would only use 1% of the features of a library, it does not justify reimplementing that 1% if that code already sits within the same project (kernel selftests). > > - I'm not too much familiar with selftests/rseq, but it seems it need heavy > rework before it can become tools/lib/librseq.so. However, I'm not sure if > the effort is worthwhile. The newly added library is fully used by > testtests/rseq. ~5% of that is going to be used by selftests/kvm. > In this case, we still have cross-dependency issue. No, it's just moving files around and a bit of Makefile modifications. That's the simple part. > > I personally prefer not to use selftests/rseq/librseq.so or add > tools/lib/librseq.so, > but I need your feedback. Please share your thoughts. I strongly favor that we use a two steps approach: 1) immediate fix: include ../rseq/rseq.c into your test code and use the headers, as proposed by Paolo. 2) I'll move librseq code into tools/lib/ and tools/include/rseq/, and adapt the users accordingly. (after the end of my vacation) Thanks, Mathieu > Thanks, > Gavin -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm