From nobody Mon Apr 29 02:21:33 2024 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1502105881704342.7728558369507; Mon, 7 Aug 2017 04:38:01 -0700 (PDT) Received: from localhost ([::1]:36617 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1degMB-0006sh-L1 for importer@patchew.org; Mon, 07 Aug 2017 07:37:59 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37677) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1degLG-0006Xw-D1 for qemu-devel@nongnu.org; Mon, 07 Aug 2017 07:37:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1degLB-00024m-J1 for qemu-devel@nongnu.org; Mon, 07 Aug 2017 07:37:02 -0400 Received: from 7.mo4.mail-out.ovh.net ([178.33.253.54]:55916) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1degLB-000247-Bh for qemu-devel@nongnu.org; Mon, 07 Aug 2017 07:36:57 -0400 Received: from player694.ha.ovh.net (b6.ovh.net [213.186.33.56]) by mo4.mail-out.ovh.net (Postfix) with ESMTP id 69B6C8B65E for ; Mon, 7 Aug 2017 13:36:55 +0200 (CEST) Received: from bahia.lan (gar31-1-82-66-74-139.fbx.proxad.net [82.66.74.139]) (Authenticated sender: groug@kaod.org) by player694.ha.ovh.net (Postfix) with ESMTPA id 85C692C0081; Mon, 7 Aug 2017 13:36:50 +0200 (CEST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Mon, 07 Aug 2017 13:36:44 +0200 Message-ID: <150210580404.1343.7325713896658799315.stgit@bahia.lan> User-Agent: StGit/0.17.1-20-gc0b1b-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Ovh-Tracer-Id: 5825124643116521794 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrfeelkedrkedugdeggecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 178.33.253.54 Subject: [Qemu-devel] [PATCH v2] kvm: workaround build break on gcc-7.1.1 / fedora26 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Cornelia Huck , Paolo Bonzini , Philippe =?utf-8?q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Building QEMU on fedora26 with the latest gcc package fails: CC ppc64-softmmu/target/ppc/kvm.o In file included from include/sysemu/hw_accel.h:16:0, from target/ppc/kvm.c:31: target/ppc/kvm.c: In function =E2=80=98kvmppc_booke_watchdog_enable=E2=80= =99: include/sysemu/kvm.h:449:35: error: =E2=80=98args_tmp[i]=E2=80=99 may be us= ed uninitialized in this function [-Werror=3Dmaybe-uninitialized] cap.args[i] =3D args_tmp[i]; \ ^ target/ppc/kvm.c: In function =E2=80=98kvmppc_set_papr=E2=80=99: include/sysemu/kvm.h:449:35: error: =E2=80=98args_tmp[i]=E2=80=99 may be us= ed uninitialized in this function [-Werror=3Dmaybe-uninitialized] cc1: all warnings being treated as errors $ rpm -q gcc gcc-7.1.1-3.fc26.ppc64le The compiler should obviously optimize this code away when no extra agument is passed to kvm_vm_enable_cap() and kvm_vcpu_enable_cap(), but it doesn't. This bug should be fixed one day in gcc, but we can also change our code pattern so that we don't hit the issue anymore. We workaround this, by using memcpy() instead of open-coding the copy. Signed-off-by: Greg Kurz Acked-by: Cornelia Huck Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- v2: - use memcpy() --- include/sysemu/kvm.h | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h index 91fc07ee9afe..3a458f50e9f4 100644 --- a/include/sysemu/kvm.h +++ b/include/sysemu/kvm.h @@ -428,11 +428,8 @@ int kvm_vm_check_extension(KVMState *s, unsigned int e= xtension); .flags =3D cap_flags, \ }; \ uint64_t args_tmp[] =3D { __VA_ARGS__ }; \ - int i; \ - for (i =3D 0; i < (int)ARRAY_SIZE(args_tmp) && \ - i < ARRAY_SIZE(cap.args); i++) { \ - cap.args[i] =3D args_tmp[i]; \ - } \ + size_t n =3D MIN(ARRAY_SIZE(args_tmp), ARRAY_SIZE(cap.args)); \ + memcpy(cap.args, args_tmp, n * sizeof(cap.args[0])); \ kvm_vm_ioctl(s, KVM_ENABLE_CAP, &cap); \ }) =20 @@ -443,11 +440,8 @@ int kvm_vm_check_extension(KVMState *s, unsigned int e= xtension); .flags =3D cap_flags, \ }; \ uint64_t args_tmp[] =3D { __VA_ARGS__ }; \ - int i; \ - for (i =3D 0; i < (int)ARRAY_SIZE(args_tmp) && \ - i < ARRAY_SIZE(cap.args); i++) { \ - cap.args[i] =3D args_tmp[i]; \ - } \ + size_t n =3D MIN(ARRAY_SIZE(args_tmp), ARRAY_SIZE(cap.args)); \ + memcpy(cap.args, args_tmp, n * sizeof(cap.args[0])); \ kvm_vcpu_ioctl(cpu, KVM_ENABLE_CAP, &cap); \ }) =20