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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 83941C433DB for ; Mon, 22 Feb 2021 14:12:43 +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 2003664E5C for ; Mon, 22 Feb 2021 14:12:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2003664E5C 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.88092.165481 (Exim 4.92) (envelope-from ) id 1lEBwr-0008Ta-Vg; Mon, 22 Feb 2021 14:12:29 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 88092.165481; Mon, 22 Feb 2021 14:12:29 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lEBwr-0008TT-SG; Mon, 22 Feb 2021 14:12:29 +0000 Received: by outflank-mailman (input) for mailman id 88092; Mon, 22 Feb 2021 14:12:27 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lEBwp-0008TO-Qt for xen-devel@lists.xenproject.org; Mon, 22 Feb 2021 14:12:27 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 8e637493-f65c-4c81-85e4-290dd2968932; Mon, 22 Feb 2021 14:12:27 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2AE18ACBF; Mon, 22 Feb 2021 14:12:26 +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: 8e637493-f65c-4c81-85e4-290dd2968932 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=1614003146; 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=2/u0KYvjfvVBPZ+ouLLVqw7o5ez4RuTOPoh1vjJdpMc=; b=GU96mxdwLML8CRLKpH3NZNbNuGRRqqzhbkXem5xuXIbdDGrPFIZ0yqkqfVXeD+3yXHB6wU yiy+6duwjtHkq3XmJW7HvIQUylH8wKZjKNFke3ufoyCc6M3pp6fZgJeojlqxAvYSynGQbl lwl8G3Ydz/DrawhKGSXmUnerzfVK3Do= Subject: Re: [PATCH][4.15] x86: mirror compat argument translation area for 32-bit PV To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: "xen-devel@lists.xenproject.org" , Andrew Cooper , Wei Liu , Ian Jackson References: From: Jan Beulich Message-ID: Date: Mon, 22 Feb 2021 15:12:25 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 22.02.2021 12:35, Roger Pau Monné wrote: > On Mon, Feb 22, 2021 at 11:27:07AM +0100, Jan Beulich wrote: >> Now that we guard the entire Xen VA space against speculative abuse >> through hypervisor accesses to guest memory, the argument translation >> area's VA also needs to live outside this range, at least for 32-bit PV >> guests. To avoid extra is_hvm_*() conditionals, use the alternative VA >> uniformly. > > Since you are double mapping the per-domain virtual area, won't it > make more sense to map it just once outside of the Xen virtual space > area? (so it's always using PML4_ADDR(511)) This would then require conditionals in paths using other parts of the per-domain mappings for 64-bit PV, as the same range is under guest control there. > Is there anything concerning in the per-domain area that should be > protected against speculative accesses? First of all this is an unrelated question - I'm not changing what gets accessed there, but only through which addresses these accesses happen. What lives there are GDT/LDT mappings, map cache, and the argument translation area. The guest has no control (or very limited when considering GDT/LDT one) over the accesses made to this space. Jan