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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 854D3C54E4A for ; Tue, 12 May 2020 13:59:02 +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 590DB20674 for ; Tue, 12 May 2020 13:59:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 590DB20674 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jYVQo-0006bQ-Td; Tue, 12 May 2020 13:58:50 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jYVQn-0006bK-Mx for xen-devel@lists.xenproject.org; Tue, 12 May 2020 13:58:49 +0000 X-Inumbo-ID: b410fac6-9458-11ea-b07b-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id b410fac6-9458-11ea-b07b-bc764e2007e4; Tue, 12 May 2020 13:58:49 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 03A5EAE56; Tue, 12 May 2020 13:58:50 +0000 (UTC) Subject: Re: [PATCH 06/16] x86/traps: Implement #CP handler and extend #PF for shadow stacks To: Andrew Cooper References: <20200501225838.9866-1-andrew.cooper3@citrix.com> <20200501225838.9866-7-andrew.cooper3@citrix.com> <561914ce-d076-8f1a-e74b-7c37567480a1@suse.com> From: Jan Beulich Message-ID: <2bab5512-2bcb-7b92-f4ac-d21e89b748d8@suse.com> Date: Tue, 12 May 2020 15:58:48 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Xen-devel , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 11.05.2020 19:20, Andrew Cooper wrote: > On 04/05/2020 15:10, Jan Beulich wrote: >> On 02.05.2020 00:58, Andrew Cooper wrote: >>> @@ -1457,6 +1451,10 @@ void do_page_fault(struct cpu_user_regs *regs) >>> { >>> enum pf_type pf_type = spurious_page_fault(addr, regs); >>> >>> + /* Any fault on a shadow stack access is a bug in Xen. */ >>> + if ( error_code & PFEC_shstk ) >>> + goto fatal; >> Not going through the full spurious_page_fault() in this case >> would seem desirable, as would be at least a respective >> adjustment to __page_fault_type(). Perhaps such an adjustment >> could then avoid the change (and the need for goto) here? > > This seems to do a lot of things which have little/nothing to do with > spurious faults. > > In particular, we don't need to disable interrupts to look at > PFEC_shstk, or RSVD for that matter. Perhaps even more so a reason to make spurious_page_fault() return a new enum pf_type enumerator? In any event your reply looks more like a "yes" to my suggestion than an objection, but I may be getting it entirely wrong ... Jan