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 X-Spam-Level: X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D57CC433E0 for ; Thu, 14 Jan 2021 15:07:54 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BED8C23A69 for ; Thu, 14 Jan 2021 15:07:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BED8C23A69 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.67104.119493 (Exim 4.92) (envelope-from ) id 1l04Ds-0005yG-8p; Thu, 14 Jan 2021 15:07:40 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 67104.119493; Thu, 14 Jan 2021 15:07:40 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l04Ds-0005y9-5c; Thu, 14 Jan 2021 15:07:40 +0000 Received: by outflank-mailman (input) for mailman id 67104; Thu, 14 Jan 2021 15:07:38 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l04Dq-0005xw-Se for xen-devel@lists.xenproject.org; Thu, 14 Jan 2021 15:07:38 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 46b1bee5-db7f-46be-a17a-9a2e928cb4a8; Thu, 14 Jan 2021 15:07:38 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 71E0CAC24; Thu, 14 Jan 2021 15:07:37 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 46b1bee5-db7f-46be-a17a-9a2e928cb4a8 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1610636857; h=from:from:reply-to: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=e67EQSav/B2t339nJdJXrH2VD3Eb4kam/ZfJ4x2oFeo=; b=lm4hQtOB9+KiI16TV/CjhfkbYZz4L25k5bT4rgjNG5BXJWylkl7JwmNFVV6Plp8f8HGLtv IhaIihyk94bt/LVdHhvgMbffWmjKA4RC3Y27VzWTMgbxako6kszjoryUEBRRMjFBSZeEBj CtkA+HHchx97AdMnINR30bWYsTvhtCk= Subject: [PATCH 09/17] x86/PV: use get_unsafe() instead of copy_from_unsafe() From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Tim Deegan , George Dunlap References: <4f1975a9-bdd9-f556-9db5-eb6c428f258f@suse.com> Message-ID: <810ebd98-6ed6-a492-0fd4-6a39d04f875b@suse.com> Date: Thu, 14 Jan 2021 16:07:37 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <4f1975a9-bdd9-f556-9db5-eb6c428f258f@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit The former expands to a single (memory accessing) insn, which the latter does not guarantee. Yet we'd prefer to read consistent PTEs rather than risking a split read racing with an update done elsewhere. Signed-off-by: Jan Beulich --- a/xen/arch/x86/pv/mm.c +++ b/xen/arch/x86/pv/mm.c @@ -41,9 +41,7 @@ l1_pgentry_t *map_guest_l1e(unsigned lon return NULL; /* Find this l1e and its enclosing l1mfn in the linear map. */ - if ( copy_from_unsafe(&l2e, - &__linear_l2_table[l2_linear_offset(linear)], - sizeof(l2_pgentry_t)) ) + if ( get_unsafe(l2e, &__linear_l2_table[l2_linear_offset(linear)]) ) return NULL; /* Check flags that it will be safe to read the l1e. */ --- a/xen/arch/x86/pv/mm.h +++ b/xen/arch/x86/pv/mm.h @@ -22,9 +22,7 @@ static inline l1_pgentry_t guest_get_eff toggle_guest_pt(curr); if ( unlikely(!__addr_ok(linear)) || - copy_from_unsafe(&l1e, - &__linear_l1_table[l1_linear_offset(linear)], - sizeof(l1_pgentry_t)) ) + get_unsafe(l1e, &__linear_l1_table[l1_linear_offset(linear)]) ) l1e = l1e_empty(); if ( user_mode )