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 01A50C19F2D for ; Tue, 9 Aug 2022 12:57:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241573AbiHIM5s (ORCPT ); Tue, 9 Aug 2022 08:57:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243101AbiHIM5m (ORCPT ); Tue, 9 Aug 2022 08:57:42 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0F09E14D2E for ; Tue, 9 Aug 2022 05:57:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1660049861; 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: in-reply-to:in-reply-to:references:references; bh=F3cWe7pcfL+jSpxT9+fiiD647kCcCtDZS7mj9Rl3zBQ=; b=b6HvVomhT9PBiUygDb7faYgEUhCijnr0/Kr6wBQ4ep3t3mDQHtqiyBaXppShaYbhSejhLL opxnybZiWu2xsH6fL+uJwq6pdGbVsMofDgjgXaIeZUqWJynL0g4g/UMNyP+xA/pAqyaTor 12KapC4w8baFrM+kvwxa1uWOvUhvh+8= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-618-9t-xeZLtOLOdMrtwy8LQIQ-1; Tue, 09 Aug 2022 08:57:34 -0400 X-MC-Unique: 9t-xeZLtOLOdMrtwy8LQIQ-1 Received: by mail-ed1-f70.google.com with SMTP id w5-20020a05640234c500b0043dda025648so7200791edc.8 for ; Tue, 09 Aug 2022 05:57:34 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:subject:from:references:cc:to :content-language:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc; bh=F3cWe7pcfL+jSpxT9+fiiD647kCcCtDZS7mj9Rl3zBQ=; b=KYUIB7PU4aB8Xdnd9LMJnqYkxxQKwSH9zsyag3cuLrEz1N714QnBXZ/I7EAfr/BTkp /+fIDGft9SUlabpitoU4vVFBtN70qI7VLHpprPYKIkfi1+wqX0+t1TesUK0Ln/SNbWQa vuo6+Pyv5Faec+aaF5BA+z9NIvshcge/tOyEyR7cQRc5PoM1ZTBh0aUzJr0yEaoPsFro jzrcoj916ro9oJwWklaxPuMj5CAy0AosDPrb9yfJG7KXZneXInpZjkniNPDQAHh3S8EW rkXvYLI3Cdv3lD2xhhX6J4tVnAL4NLEMgk/LC3z1kkm+oGeNHO5k5gHfBz6ZOfe7VH/Q ceIw== X-Gm-Message-State: ACgBeo2ALLtV+Xhp51WJ1SoieiaiJg/LW7pRbzxiN/0FyUCjV1MXCxt1 Kd+S85U5q6Zc+cSbQW6Ojm5ZHW73DR5ESd38CcFeRib1J9KdTLMIe6GnvU4WSKK+x9XQzJ7yjQ6 YTc1cjO63T7Bu2rGY2n+Dy2s6 X-Received: by 2002:a50:ff04:0:b0:43d:67a7:dd2d with SMTP id a4-20020a50ff04000000b0043d67a7dd2dmr21829916edu.11.1660049853469; Tue, 09 Aug 2022 05:57:33 -0700 (PDT) X-Google-Smtp-Source: AA6agR5GIr5QJ52aSSx6gxZKOjLvTfr2Ce6VOb3LUggNaFF2sRhog+jgdqCgASBpgj2vWfyB2CEL6w== X-Received: by 2002:a50:ff04:0:b0:43d:67a7:dd2d with SMTP id a4-20020a50ff04000000b0043d67a7dd2dmr21829900edu.11.1660049853298; Tue, 09 Aug 2022 05:57:33 -0700 (PDT) Received: from ?IPV6:2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e? ([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.googlemail.com with ESMTPSA id y2-20020a170906070200b007306df330e5sm1131474ejb.12.2022.08.09.05.57.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Aug 2022 05:57:32 -0700 (PDT) Message-ID: <36634375-e7ee-e28e-20dd-9ab1ebdd8040@redhat.com> Date: Tue, 9 Aug 2022 14:57:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Content-Language: en-US To: Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Matlack , Yan Zhao , Mingwei Zhang , Ben Gardon References: <20220805230513.148869-1-seanjc@google.com> <20220805230513.148869-9-seanjc@google.com> From: Paolo Bonzini Subject: Re: [PATCH v3 8/8] KVM: x86/mmu: explicitly check nx_hugepage in disallowed_hugepage_adjust() In-Reply-To: <20220805230513.148869-9-seanjc@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/6/22 01:05, Sean Christopherson wrote: > !is_large_pte(spte)) { > + u64 page_mask; > + > + /* > + * Ensure nx_huge_page_disallowed is read after checking for a > + * present shadow page. A different vCPU may be concurrently > + * installing the shadow page if mmu_lock is held for read. > + * Pairs with the smp_wmb() in kvm_tdp_mmu_map(). > + */ > + smp_rmb(); > + > + if (!spte_to_child_sp(spte)->nx_huge_page_disallowed) > + return; > + I wonder if the barrier shouldn't be simply in to_shadow_page(), i.e. always assume in the TDP MMU code that sp->xyz is read after the SPTE that points to that struct kvm_mmu_page. Paolo