From patchwork Tue Nov 26 10:25:14 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Heiko Carstens X-Patchwork-Id: 13885765 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D2E08195FEF; Tue, 26 Nov 2024 10:25:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732616725; cv=none; b=fowsAQRkQWt3gkWSS21D6D0LsfPr3tV03wsV/GiViXWJFzU1ST9SUY2q1XXGdfmiRtXQAEbU2LIFsnQRrxF0NxcgNmtV2lCF9qkVSNU0pCqFqOSigRBEDl/QbjaIZdXBxnGWzZoTj25zd0mbXqYA3+gqSHzobmoLcQNRr0Yxhjw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732616725; c=relaxed/simple; bh=KRRHVbmHfv7a0GjaWgtrBM521TCMysRPfuKXqff72sQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iH3bxiId+Fmot1SsXs0UcSnrME6/w6HrBr1pSrjVDoOrb+L10HqV00WPpbi+dIxvNmHdPN4J50GCopNFmSY2gjweQrlkV5y493764D/h09kqOkQe+u4mt12UE6LXgutsUfCANkGMUHu0Foe8XhBrXSXgWLav/Cxb+uRZKh+uR9c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=napG3UMQ; arc=none smtp.client-ip=148.163.158.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="napG3UMQ" Received: from pps.filterd (m0353725.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 4AQ6r004020137; Tue, 26 Nov 2024 10:25:21 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:date:from:in-reply-to:message-id :mime-version:references:subject:to; s=pp1; bh=Z5PQGf94hDkjfa+R4 Y+KBYYblAtkWCHqKfOzDX4wmaY=; b=napG3UMQYTBBCu144xB5MT49UKFB6fzJC MVCsrnszCJ4hKstVQjlBmarMg91AVm8hIreQ8zac08ynJxdsBDu968Dd11M87SzN mAcvJD2ijPpUr1yKVuU54HrK3+OSMDGtuaiDXcb0jan3YL/PTS11abx2j6Zu9h3x VtNUsq67CwI+f3Yeha52yHULxc0qPTUxPSDqw9kplbAC+doyqxRW2gwuwDFmw/za 4CS6y32nAzss5qzWB+YQyaElH6/LZ+Ie08zzpOrzeGz0rYkjubdZU92ADX4ZBSbw +1ZHZ/KuuUjACKogCOnOc/FlK0D3B+KK5ARtDcTfKSQKf/HenmkSw== Received: from ppma13.dal12v.mail.ibm.com (dd.9e.1632.ip4.static.sl-reverse.com [50.22.158.221]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 43386jw0yj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 26 Nov 2024 10:25:20 +0000 (GMT) Received: from pps.filterd (ppma13.dal12v.mail.ibm.com [127.0.0.1]) by ppma13.dal12v.mail.ibm.com (8.18.1.2/8.18.1.2) with ESMTP id 4AQ3xd28027470; Tue, 26 Nov 2024 10:25:20 GMT Received: from smtprelay04.fra02v.mail.ibm.com ([9.218.2.228]) by ppma13.dal12v.mail.ibm.com (PPS) with ESMTPS id 433ukj46rr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 26 Nov 2024 10:25:20 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 4AQAPGdF27198006 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Nov 2024 10:25:16 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 977C120077; Tue, 26 Nov 2024 10:25:16 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 73E5B2007A; Tue, 26 Nov 2024 10:25:16 +0000 (GMT) Received: from tuxmaker.lnxne.boe (unknown [9.152.85.9]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 26 Nov 2024 10:25:16 +0000 (GMT) From: Heiko Carstens To: Christian Borntraeger , Janosch Frank , Claudio Imbrenda , David Hildenbrand Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/3] KVM: s390: Remove one byte cmpxchg() usage Date: Tue, 26 Nov 2024 11:25:14 +0100 Message-ID: <20241126102515.3178914-3-hca@linux.ibm.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20241126102515.3178914-1-hca@linux.ibm.com> References: <20241126102515.3178914-1-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 0UO_Ox1IU_CK-A74SclxwLpWQPRF6zto X-Proofpoint-GUID: 0UO_Ox1IU_CK-A74SclxwLpWQPRF6zto X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 malwarescore=0 mlxlogscore=998 spamscore=0 suspectscore=0 phishscore=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 impostorscore=0 adultscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2411260079 Within sca_clear_ext_call() cmpxchg() is used to clear one or two bytes (depending on sca format). The cmpxchg() calls are not supposed to fail; if so that would be a bug. Given that cmpxchg() usage on one and two byte areas generates very inefficient code, replace them with block concurrent WRITE_ONCE() calls, and remove the WARN_ON(). Acked-by: Claudio Imbrenda Signed-off-by: Heiko Carstens --- arch/s390/kvm/interrupt.c | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index eff69018cbeb..ea8dce299954 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -118,8 +118,6 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id) static void sca_clear_ext_call(struct kvm_vcpu *vcpu) { - int rc, expect; - if (!kvm_s390_use_sca_entries()) return; kvm_s390_clear_cpuflags(vcpu, CPUSTAT_ECALL_PEND); @@ -128,23 +126,16 @@ static void sca_clear_ext_call(struct kvm_vcpu *vcpu) struct esca_block *sca = vcpu->kvm->arch.sca; union esca_sigp_ctrl *sigp_ctrl = &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union esca_sigp_ctrl old; - old = READ_ONCE(*sigp_ctrl); - expect = old.value; - rc = cmpxchg(&sigp_ctrl->value, old.value, 0); + WRITE_ONCE(sigp_ctrl->value, 0); } else { struct bsca_block *sca = vcpu->kvm->arch.sca; union bsca_sigp_ctrl *sigp_ctrl = &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); - union bsca_sigp_ctrl old; - old = READ_ONCE(*sigp_ctrl); - expect = old.value; - rc = cmpxchg(&sigp_ctrl->value, old.value, 0); + WRITE_ONCE(sigp_ctrl->value, 0); } read_unlock(&vcpu->kvm->arch.sca_lock); - WARN_ON(rc != expect); /* cannot clear? */ } int psw_extint_disabled(struct kvm_vcpu *vcpu)