From nobody Tue Sep 16 00:36:17 2025 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 1C6F3C54EBE for ; Mon, 9 Jan 2023 12:52:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234065AbjAIMwG (ORCPT ); Mon, 9 Jan 2023 07:52:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230499AbjAIMvx (ORCPT ); Mon, 9 Jan 2023 07:51:53 -0500 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 40D55B06; Mon, 9 Jan 2023 04:51:51 -0800 (PST) Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 309BP0E7016670; Mon, 9 Jan 2023 12:51:51 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding; s=pp1; bh=OacVvB18McZxLNMXZ4NRfCDUji0la1y9ALJrNWFwFLE=; b=h51lh38MrlTHkSBeIFmNSJfQxPpDxyFPlQwMWOCQ5yJSDP5XbETnwGe29+5J11EphkTU RkZ/QMuFCbJe1fFerXbN7ocRbeLHROZY7eEFP+nfJPhSu4LJPXjqjf9IVVOKXgeNVVYY rmkhud7aSuiI8Ta32ZluwdlZGimZjwv3Eo4WK7ZuJdCeoVViWxQ2WuXkfHf6f4sM0pyc FcYd2u2o9N3yCy18Vxb8jPlBfSZ6wON05TZHIYF/Mbj3Wi+Nk6bNNfyeUd3M8/1bQoIC vKuCBb3k7ITGIMoF6X62fhFA9//dUeqbUNYA0tjna60G8g280eW180/Ef52iPQn03BHL Ww== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3myj6jdbsm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 09 Jan 2023 12:51:50 +0000 Received: from m0098399.ppops.net (m0098399.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 309Bi1tx029590; Mon, 9 Jan 2023 12:51:42 GMT Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3myj6jdbs7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 09 Jan 2023 12:51:42 +0000 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 3098Vw80015062; Mon, 9 Jan 2023 12:51:39 GMT Received: from smtprelay03.fra02v.mail.ibm.com ([9.218.2.224]) by ppma06ams.nl.ibm.com (PPS) with ESMTPS id 3my00fjybq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 09 Jan 2023 12:51:39 +0000 Received: from smtpav01.fra02v.mail.ibm.com (smtpav01.fra02v.mail.ibm.com [10.20.54.100]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 309CpaVX43581774 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 9 Jan 2023 12:51:36 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 15E6A20040; Mon, 9 Jan 2023 12:51:36 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C86BB20049; Mon, 9 Jan 2023 12:51:35 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 9 Jan 2023 12:51:35 +0000 (GMT) From: Heiko Carstens To: Christian Borntraeger , Janosch Frank , Claudio Imbrenda Cc: David Hildenbrand , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] KVM: s390: interrupt: use READ_ONCE() before cmpxchg() Date: Mon, 9 Jan 2023 13:51:35 +0100 Message-Id: <20230109125135.393784-1-hca@linux.ibm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: AzKIpn3LWjZZNpfB9gis_V1SVAfvtPpx X-Proofpoint-GUID: -aFgml4fVU3jhLtYfr56yl_d8uZadMCI X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.923,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2023-01-09_06,2023-01-09_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 lowpriorityscore=0 mlxlogscore=712 phishscore=0 adultscore=0 mlxscore=0 suspectscore=0 impostorscore=0 priorityscore=1501 bulkscore=0 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2301090090 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Use READ_ONCE() before cmpxchg() to prevent that the compiler generates code that fetches the to be compared old value several times from memory. Signed-off-by: Heiko Carstens --- arch/s390/kvm/interrupt.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index 1dae78deddf2..a3bf1b6a7962 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -83,8 +83,9 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int= src_id) struct esca_block *sca =3D vcpu->kvm->arch.sca; union esca_sigp_ctrl *sigp_ctrl =3D &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union esca_sigp_ctrl new_val =3D {0}, old_val =3D *sigp_ctrl; + union esca_sigp_ctrl new_val =3D {0}; =20 + old_val =3D READ_ONCE(*sigp_ctrl); new_val.scn =3D src_id; new_val.c =3D 1; old_val.c =3D 0; @@ -95,8 +96,9 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int= src_id) struct bsca_block *sca =3D vcpu->kvm->arch.sca; union bsca_sigp_ctrl *sigp_ctrl =3D &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union bsca_sigp_ctrl new_val =3D {0}, old_val =3D *sigp_ctrl; + union bsca_sigp_ctrl new_val =3D {0}; =20 + old_val =3D READ_ONCE(*sigp_ctrl); new_val.scn =3D src_id; new_val.c =3D 1; old_val.c =3D 0; @@ -126,16 +128,18 @@ static void sca_clear_ext_call(struct kvm_vcpu *vcpu) struct esca_block *sca =3D vcpu->kvm->arch.sca; union esca_sigp_ctrl *sigp_ctrl =3D &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union esca_sigp_ctrl old =3D *sigp_ctrl; + union esca_sigp_ctrl old; =20 + old =3D READ_ONCE(*sigp_ctrl); expect =3D old.value; rc =3D cmpxchg(&sigp_ctrl->value, old.value, 0); } else { struct bsca_block *sca =3D vcpu->kvm->arch.sca; union bsca_sigp_ctrl *sigp_ctrl =3D &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union bsca_sigp_ctrl old =3D *sigp_ctrl; + union bsca_sigp_ctrl old; =20 + old =3D READ_ONCE(*sigp_ctrl); expect =3D old.value; rc =3D cmpxchg(&sigp_ctrl->value, old.value, 0); } --=20 2.34.1