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 0C92DECAAA1 for ; Fri, 9 Sep 2022 18:56:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229712AbiIIS4z (ORCPT ); Fri, 9 Sep 2022 14:56:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229813AbiIIS4y (ORCPT ); Fri, 9 Sep 2022 14:56:54 -0400 Received: from smtp-fw-80006.amazon.com (smtp-fw-80006.amazon.com [99.78.197.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80222EB852 for ; Fri, 9 Sep 2022 11:56:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1662749813; x=1694285813; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=gMuDDfCUmqYcJCT4kSblyTa1PE5mR8p1E7LTS0IsYMY=; b=cWpore6vF5sEyC27tm0GqUykgFMxXsaxzjc4cJqn8bSxdEf2enSrfJZ+ MCZoaTOe6ZKWV1OtRskpo9IdnN17sGs+bscZk8By+glAYcnXUapr+KEBi i76HJJhzqg9n/QxOzrK9pypEDC9LHD2FfjqpwuVamf786XoaoHuywNw75 Q=; X-IronPort-AV: E=Sophos;i="5.93,303,1654560000"; d="scan'208";a="128517776" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-iad-1d-b48bc93b.us-east-1.amazon.com) ([10.25.36.210]) by smtp-border-fw-80006.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2022 18:56:52 +0000 Received: from EX13MTAUWB001.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan3.iad.amazon.com [10.40.163.38]) by email-inbound-relay-iad-1d-b48bc93b.us-east-1.amazon.com (Postfix) with ESMTPS id 15302C08DB; Fri, 9 Sep 2022 18:56:48 +0000 (UTC) Received: from EX19D012UWB001.ant.amazon.com (10.13.138.50) by EX13MTAUWB001.ant.amazon.com (10.43.161.207) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Fri, 9 Sep 2022 18:56:21 +0000 Received: from EX13MTAUEE002.ant.amazon.com (10.43.62.24) by EX19D012UWB001.ant.amazon.com (10.13.138.50) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.1118.12; Fri, 9 Sep 2022 18:56:21 +0000 Received: from dev-dsk-risbhat-2b-8bdc64cd.us-west-2.amazon.com (10.189.73.169) by mail-relay.amazon.com (10.43.62.224) with Microsoft SMTP Server id 15.0.1497.38 via Frontend Transport; Fri, 9 Sep 2022 18:56:20 +0000 Received: by dev-dsk-risbhat-2b-8bdc64cd.us-west-2.amazon.com (Postfix, from userid 22673075) id 8D10958A5; Fri, 9 Sep 2022 18:56:19 +0000 (UTC) From: Rishabh Bhatnagar To: CC: , , , , , , , , , , , , "Lai Jiangshan" , Rishabh Bhatnagar Subject: [PATCH 1/9] KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior Date: Fri, 9 Sep 2022 18:55:49 +0000 Message-ID: <20220909185557.21255-2-risbhat@amazon.com> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220909185557.21255-1-risbhat@amazon.com> References: <20220909185557.21255-1-risbhat@amazon.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Lai Jiangshan commit af3511ff7fa2107d6410831f3d71030f5e8d2b25 upstream. In record_steal_time(), st->preempted is read twice, and trace_kvm_pv_tlb_flush() might output result inconsistent if kvm_vcpu_flush_tlb_guest() see a different st->preempted later. It is a very trivial problem and hardly has actual harm and can be avoided by reseting and reading st->preempted in atomic way via xchg(). Signed-off-by: Lai Jiangshan Message-Id: <20210531174628.10265-1-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini Signed-off-by: Rishabh Bhatnagar --- arch/x86/kvm/x86.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c5a08ec348e6..3640b298c42e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3032,9 +3032,11 @@ static void record_steal_time(struct kvm_vcpu *vcpu) * expensive IPIs. */ if (guest_pv_has(vcpu, KVM_FEATURE_PV_TLB_FLUSH)) { + u8 st_preempted = xchg(&st->preempted, 0); + trace_kvm_pv_tlb_flush(vcpu->vcpu_id, - st->preempted & KVM_VCPU_FLUSH_TLB); - if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB) + st_preempted & KVM_VCPU_FLUSH_TLB); + if (st_preempted & KVM_VCPU_FLUSH_TLB) kvm_vcpu_flush_tlb_guest(vcpu); } else { st->preempted = 0; -- 2.37.1