From nobody Sat Apr 11 15:29:12 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 953B5C00140 for ; Wed, 10 Aug 2022 10:42:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231501AbiHJKm3 (ORCPT ); Wed, 10 Aug 2022 06:42:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39564 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231610AbiHJKmR (ORCPT ); Wed, 10 Aug 2022 06:42:17 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 611226C768 for ; Wed, 10 Aug 2022 03:42:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1660128133; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TwW6M6u5vKyxDnMqx9AQR/gg33wHCbXk3i4GrhHVUrQ=; b=g2wHHsvVTkMiXQDEhAO1EuLOYvJA4va0ihuWBBHsYqWobAg4sgxsVVPBiSlcB9RS3A/0// HkM1vsDirO3LjHGqKtyBQzG2KNoQnqFYToXT7Ic7OVWvDpCpVBiOyTd9otC0dbZwhw58XT MhsjsKQYUpMpA6nvd3lmPWvneJ+ueV4= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-41-gw23tJ4HN0-JU_uY1ipUDA-1; Wed, 10 Aug 2022 06:42:08 -0400 X-MC-Unique: gw23tJ4HN0-JU_uY1ipUDA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 23A693C2288C; Wed, 10 Aug 2022 10:42:08 +0000 (UTC) Received: from gshan.redhat.com (vpn2-54-77.bne.redhat.com [10.64.54.77]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 666C64050067; Wed, 10 Aug 2022 10:42:03 +0000 (UTC) From: Gavin Shan To: kvmarm@lists.cs.columbia.edu Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, fweimer@redhat.com, shan.gavin@gmail.com, maz@kernel.org, andrew.jones@linux.dev, mathieu.desnoyers@efficios.com, pbonzini@redhat.com, yihyu@redhat.com, seanjc@google.com, oliver.upton@linux.dev Subject: [PATCH v2 2/2] KVM: selftests: Use getcpu() instead of sched_getcpu() in rseq_test Date: Wed, 10 Aug 2022 18:41:14 +0800 Message-Id: <20220810104114.6838-3-gshan@redhat.com> In-Reply-To: <20220810104114.6838-1-gshan@redhat.com> References: <20220810104114.6838-1-gshan@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" sched_getcpu() is glibc dependent and it can simply return the CPU ID from the registered rseq information, as Florian Weimer pointed. In this case, it's pointless to compare the return value from sched_getcpu() and that fetched from the registered rseq information. Fix the issue by replacing sched_getcpu() with getcpu(), as Florian suggested. The comments are modified accordingly by replacing "sched_getcpu()" with "getcpu()". Reported-by: Yihuang Yu Suggested-by: Florian Weimer Suggested-by: Mathieu Desnoyers Suggested-by: Sean Christopherson Signed-off-by: Gavin Shan --- tools/testing/selftests/kvm/rseq_test.c | 42 ++++++++++++++++--------- 1 file changed, 27 insertions(+), 15 deletions(-) diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selfte= sts/kvm/rseq_test.c index 2cd5fe49ac8b..84e8425edc2c 100644 --- a/tools/testing/selftests/kvm/rseq_test.c +++ b/tools/testing/selftests/kvm/rseq_test.c @@ -42,6 +42,18 @@ static void guest_code(void) GUEST_SYNC(0); } =20 +/* + * We have to perform direct system call for getcpu() because it's + * not available until glic 2.29. + */ +static void sys_getcpu(unsigned *cpu) +{ + int r; + + r =3D syscall(__NR_getcpu, cpu, NULL, NULL); + TEST_ASSERT(!r, "getcpu failed, errno =3D %d (%s)", errno, strerror(errno= )); +} + static int next_cpu(int cpu) { /* @@ -86,7 +98,7 @@ static void *migration_worker(void *__rseq_tid) atomic_inc(&seq_cnt); =20 /* - * Ensure the odd count is visible while sched_getcpu() isn't + * Ensure the odd count is visible while getcpu() isn't * stable, i.e. while changing affinity is in-progress. */ smp_wmb(); @@ -127,10 +139,10 @@ static void *migration_worker(void *__rseq_tid) * check completes. * * 3. To ensure the read-side makes efficient forward progress, - * e.g. if sched_getcpu() involves a syscall. Stalling the - * read-side means the test will spend more time waiting for - * sched_getcpu() to stabilize and less time trying to hit - * the timing-dependent bug. + * e.g. if getcpu() involves a syscall. Stalling the read-side + * means the test will spend more time waiting for getcpu() + * to stabilize and less time trying to hit the timing-dependent + * bug. * * Because any bug in this area is likely to be timing-dependent, * run with a range of delays at 1us intervals from 1us to 10us @@ -226,9 +238,9 @@ int main(int argc, char *argv[]) =20 /* * Verify rseq's CPU matches sched's CPU. Ensure migration - * doesn't occur between sched_getcpu() and reading the rseq - * cpu_id by rereading both if the sequence count changes, or - * if the count is odd (migration in-progress). + * doesn't occur between getcpu() and reading the rseq cpu_id + * by rereading both if the sequence count changes, or if the + * count is odd (migration in-progress). */ do { /* @@ -238,12 +250,12 @@ int main(int argc, char *argv[]) snapshot =3D atomic_read(&seq_cnt) & ~1; =20 /* - * Ensure reading sched_getcpu() and rseq.cpu_id - * complete in a single "no migration" window, i.e. are - * not reordered across the seq_cnt reads. + * Ensure reading getcpu() and rseq.cpu_id complete in + * a single "no migration" window, i.e. are not reordered + * across the seq_cnt reads. */ smp_rmb(); - cpu =3D sched_getcpu(); + sys_getcpu(&cpu); rseq_cpu =3D READ_ONCE(__rseq->cpu_id); smp_rmb(); } while (snapshot !=3D atomic_read(&seq_cnt)); @@ -255,9 +267,9 @@ int main(int argc, char *argv[]) /* * Sanity check that the test was able to enter the guest a reasonable * number of times, e.g. didn't get stalled too often/long waiting for - * sched_getcpu() to stabilize. A 2:1 migration:KVM_RUN ratio is a - * fairly conservative ratio on x86-64, which can do _more_ KVM_RUNs - * than migrations given the 1us+ delay in the migration task. + * getcpu() to stabilize. A 2:1 migration:KVM_RUN ratio is a fairly + * conservative ratio on x86-64, which can do _more_ KVM_RUNs than + * migrations given the 1us+ delay in the migration task. */ TEST_ASSERT(i > (NR_TASK_MIGRATIONS / 2), "Only performed %d KVM_RUNs, task stalled too much?\n", i); --=20 2.23.0