From mboxrd@z Thu Jan 1 00:00:00 1970 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 D26CDC7112F for ; Mon, 16 Jan 2023 14:14:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232324AbjAPOOy (ORCPT ); Mon, 16 Jan 2023 09:14:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40732 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232500AbjAPONq (ORCPT ); Mon, 16 Jan 2023 09:13:46 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85A6725E08; Mon, 16 Jan 2023 06:05:14 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 203BFB80FA3; Mon, 16 Jan 2023 14:05:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BFC69C433F2; Mon, 16 Jan 2023 14:05:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673877912; bh=ssVnZrCTN+KYvMaSdEtcY+L24YAGnLtGwEcEJ5KZZVM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=d0WZbRtxQWH5VeOUDONg2Z+pnRf6epapKbXWagka0iU8wA013qmeoq8/g0S+Ez8ex FCakD8mnEepNV+Kb+YZEs9xDQHepivxRA++m/Rl3pF5goGxlLElDOA9jKCiUzrsVua JoBIo4ydEofnrS19xvBzzTsPZAkJYDlwuz2A7HAcRxYuJgcAb5nO0BI1ZGZphrUXf4 KgR2QGTmeSO79vqxfBYyhsOh8iDuElqNTzgUnFSG1qnA6uDyMNfG6zrENk9BFRLYxf rXqffq2o+LnCVlYPhOqm/t5KfQjCQaB0yMtRJkFNPYXrLoaDs1R2Xz8TgkAToULFpa wHBOm0JFypOUw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Heiko Carstens , Christian Borntraeger , Claudio Imbrenda , Sasha Levin , frankja@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org Subject: [PATCH AUTOSEL 5.10 13/17] KVM: s390: interrupt: use READ_ONCE() before cmpxchg() Date: Mon, 16 Jan 2023 09:04:44 -0500 Message-Id: <20230116140448.116034-13-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20230116140448.116034-1-sashal@kernel.org> References: <20230116140448.116034-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Heiko Carstens [ Upstream commit 42400d99e9f0728c17240edb9645637ead40f6b9 ] Use READ_ONCE() before cmpxchg() to prevent that the compiler generates code that fetches the to be compared old value several times from memory. Reviewed-by: Christian Borntraeger Acked-by: Christian Borntraeger Reviewed-by: Claudio Imbrenda Link: https://lore.kernel.org/r/20230109145456.2895385-1-hca@linux.ibm.com Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin --- 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 b51ab19eb972..64d1dfe6dca5 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -81,8 +81,9 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id) 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 new_val = {0}, old_val = *sigp_ctrl; + union esca_sigp_ctrl new_val = {0}, old_val; + old_val = READ_ONCE(*sigp_ctrl); new_val.scn = src_id; new_val.c = 1; old_val.c = 0; @@ -93,8 +94,9 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id) 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 new_val = {0}, old_val = *sigp_ctrl; + union bsca_sigp_ctrl new_val = {0}, old_val; + old_val = READ_ONCE(*sigp_ctrl); new_val.scn = src_id; new_val.c = 1; old_val.c = 0; @@ -124,16 +126,18 @@ 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 = *sigp_ctrl; + union esca_sigp_ctrl old; + old = READ_ONCE(*sigp_ctrl); expect = old.value; rc = cmpxchg(&sigp_ctrl->value, old.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 = *sigp_ctrl; + union bsca_sigp_ctrl old; + old = READ_ONCE(*sigp_ctrl); expect = old.value; rc = cmpxchg(&sigp_ctrl->value, old.value, 0); } -- 2.35.1