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 D2ECCC678D8 for ; Mon, 16 Jan 2023 14:07:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232088AbjAPOHz (ORCPT ); Mon, 16 Jan 2023 09:07:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45332 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232011AbjAPOGq (ORCPT ); Mon, 16 Jan 2023 09:06:46 -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 8CE92241C4; Mon, 16 Jan 2023 06:03:32 -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 4BDF4B80E93; Mon, 16 Jan 2023 14:03:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D75EAC433EF; Mon, 16 Jan 2023 14:03:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673877810; bh=MZA7xSPsiPFWBe56xzCddWPtCG01sh+hk7C2rptTjPA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZWgtbJdWtmVYpqq1q9AK2L+tArbSdR48vVDtesWc53sL97UeLDljdrrqAFoPTAeqQ otY+KcLPcsdG6LUefLv6mdmrBtSrpS5kB/HZu+19AOqWLIm5vXADM438+8Sgzlks13 lBEn9yvgUB49vWXrWcmmUoK67xMvx3YLkQz1m4zZA/ytJmzDN1dy3V5SgdWzQFrGMD 7EpXyEtvvk/88/suY5jOn1GzegK3PBU2pmDekL7XTAwvxd34QrYpo39WiN3/EsLcUJ y29tMV3fO6ueO5oWpf23Am4R0T2P1ncD41hoDWvuNK/VcKwsgRFmktwCky/Zh0FA7h mILzdl2MKNjdQ== 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 6.1 40/53] KVM: s390: interrupt: use READ_ONCE() before cmpxchg() Date: Mon, 16 Jan 2023 09:01:40 -0500 Message-Id: <20230116140154.114951-40-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20230116140154.114951-1-sashal@kernel.org> References: <20230116140154.114951-1-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: linux-kernel@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 ab569faf0df2..6d74acea5e85 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 = 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; @@ -95,8 +96,9 @@ 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; @@ -126,16 +128,18 @@ 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