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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 459F2C0502C for ; Sat, 27 Aug 2022 08:24:37 +0000 (UTC) Received: from localhost ([::1]:46214 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oRr7L-0002rF-VU for qemu-devel@archiver.kernel.org; Sat, 27 Aug 2022 04:24:36 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50130) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oRr5c-0001zE-OJ for qemu-devel@nongnu.org; Sat, 27 Aug 2022 04:22:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:22297) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oRr5Z-0000fN-Hd for qemu-devel@nongnu.org; Sat, 27 Aug 2022 04:22:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1661588564; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=i01MZiN9ZlB6ehbZJbRtO5rOjZDPo++IqTcJOis8iYA=; b=V0GL/vPAS/JCh6PnWz3Z0z0kNYA9y/uYanInoHjueE5ssbtHOkiNklTgmuKaDNS5t1blPl umUbUQToFo4MSqkSCW+la6GImpScU24ewqg7Kop3zR76eXMFnY7ulBZ1WGIdpqHWxC6haT bX76Eq2ABqPpHgw2h0kKaWHtxpczdjM= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-604-iXDB8SwpPBiiNpxLx2xSug-1; Sat, 27 Aug 2022 04:22:42 -0400 X-MC-Unique: iXDB8SwpPBiiNpxLx2xSug-1 Received: by mail-ej1-f72.google.com with SMTP id mp41-20020a1709071b2900b0073d84b11981so1111529ejc.23 for ; Sat, 27 Aug 2022 01:22:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc; bh=i01MZiN9ZlB6ehbZJbRtO5rOjZDPo++IqTcJOis8iYA=; b=wiZmyBtYcUs3Lj1WvBMZU2au1MZupzsETJ2IM1FAfPJQJugFyqtFwRRUvSvBy8GagR HZCDnEkfBG0O2z2sEP6F9Ww54XYJCgccjY5liTdlTMphgEfcNm+d65sdL2KPiva4QpyP moPgUpQ33Y0L0Alw7eY0L1mF2nCJXND9Y0RekSCo6DZJMzzNvVU+87jrm8V6Hd1KjbR9 3MvEAS5zC9v7ea5QLYrws2jBpEeZk2+VR/epeMT9BJe2qQEwZ2G2xmUJU3vp4yXNryTM aeLdBWSzcpPy5lTWX6g6xKZNKNQQFWG2a1RWNxmCVL5wlYox2znYbmjImDc8nK/9uume xTVQ== X-Gm-Message-State: ACgBeo1DlhxmcWqL1pdi2SW6OqRuRP4rKS9j81z1fJ1CVR87xRP/0dxD t8FST1xyQiy+QhSv5mg5wJVPVnX1Yw8xhzL1DxTZaHJTEJMb9sZc+y8AyALxdq/TqC1CMAN5LL+ LEdlw4gO+rlZ4S4YUlycFlb+IDK0WSRXpqGCqkRmFPA5O/L9j+HzE38fGDUNw1Ho7ZSA= X-Received: by 2002:a17:907:75c1:b0:72f:248d:5259 with SMTP id jl1-20020a17090775c100b0072f248d5259mr7802498ejc.227.1661588561345; Sat, 27 Aug 2022 01:22:41 -0700 (PDT) X-Google-Smtp-Source: AA6agR6PQLiaYLCPk90wfUJg13fZdafK39F0pvTTTT+x2Qn7tuYOmcfXQ4GAr507tt28UN2JHm8oNg== X-Received: by 2002:a17:907:75c1:b0:72f:248d:5259 with SMTP id jl1-20020a17090775c100b0072f248d5259mr7802485ejc.227.1661588561069; Sat, 27 Aug 2022 01:22:41 -0700 (PDT) Received: from goa-sendmail ([93.56.160.208]) by smtp.gmail.com with ESMTPSA id og4-20020a1709071dc400b0073ddfe1ea69sm1797125ejc.111.2022.08.27.01.22.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 27 Aug 2022 01:22:20 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: f4bug@amsat.org, Peter Xu , Gavin Shan Subject: [PATCH v2] KVM: dirty ring: add missing memory barrier Date: Sat, 27 Aug 2022 10:22:18 +0200 Message-Id: <20220827082218.214001-1-pbonzini@redhat.com> X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" The KVM_DIRTY_GFN_F_DIRTY flag ensures that the entry is valid. If the read of the fields are not ordered after the read of the flag, QEMU might see stale values. Cc: Peter Xu Cc: Gavin Shan Signed-off-by: Paolo Bonzini --- accel/kvm/kvm-all.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 8d81ab74de..136c8eaed3 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -719,7 +719,11 @@ static void kvm_dirty_ring_mark_page(KVMState *s, uint32_t as_id, static bool dirty_gfn_is_dirtied(struct kvm_dirty_gfn *gfn) { - return gfn->flags == KVM_DIRTY_GFN_F_DIRTY; + /* + * Read the flags before the value. Pairs with barrier in + * KVM's kvm_dirty_ring_push() function. + */ + return qatomic_load_acquire(&gfn->flags) == KVM_DIRTY_GFN_F_DIRTY; } static void dirty_gfn_set_collected(struct kvm_dirty_gfn *gfn) -- 2.37.1