From patchwork Tue Jul 28 15:50:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thadeu Lima de Souza Cascardo X-Patchwork-Id: 11689455 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7F57214B7 for ; Tue, 28 Jul 2020 15:51:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 677A0206F5 for ; Tue, 28 Jul 2020 15:51:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730750AbgG1PvK (ORCPT ); Tue, 28 Jul 2020 11:51:10 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:59651 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730671AbgG1PvK (ORCPT ); Tue, 28 Jul 2020 11:51:10 -0400 Received: from 1.general.cascardo.us.vpn ([10.172.70.58] helo=localhost.localdomain) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1k0Rsb-0007kg-96; Tue, 28 Jul 2020 15:51:01 +0000 From: Thadeu Lima de Souza Cascardo To: Michael Ellerman Cc: Shuah Khan , cascardo@canonical.com, linuxppc-dev@lists.ozlabs.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] selftests/powerpc: return skip code for spectre_v2 Date: Tue, 28 Jul 2020 12:50:39 -0300 Message-Id: <20200728155039.401445-1-cascardo@canonical.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org When running under older versions of qemu of under newer versions with old machine types, some security features will not be reported to the guest. This will lead the guest OS to consider itself Vulnerable to spectre_v2. So, spectre_v2 test fails in such cases when the host is mitigated and miss predictions cannot be detected as expected by the test. Make it return the skip code instead, for this particular case. We don't want to miss the case when the test fails and the system reports as mitigated or not affected. But it is not a problem to miss failures when the system reports as Vulnerable. Signed-off-by: Thadeu Lima de Souza Cascardo --- tools/testing/selftests/powerpc/security/spectre_v2.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/tools/testing/selftests/powerpc/security/spectre_v2.c b/tools/testing/selftests/powerpc/security/spectre_v2.c index 8c6b982af2a8..d5445bfd63ed 100644 --- a/tools/testing/selftests/powerpc/security/spectre_v2.c +++ b/tools/testing/selftests/powerpc/security/spectre_v2.c @@ -183,6 +183,14 @@ int spectre_v2_test(void) if (miss_percent > 15) { printf("Branch misses > 15%% unexpected in this configuration!\n"); printf("Possible mis-match between reported & actual mitigation\n"); + /* Such a mismatch may be caused by a guest system + * reporting as vulnerable when the host is mitigated. + * Return skip code to avoid detecting this as an + * error. We are not vulnerable and reporting otherwise, + * so missing such a mismatch is safe. + */ + if (state == VULNERABLE) + return 4; return 1; } break;