From patchwork Fri Sep 11 10:34:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 11770271 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E2DC0139F for ; Fri, 11 Sep 2020 10:35:42 +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 BFA9B204EC for ; Fri, 11 Sep 2020 10:35:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFA9B204EC 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 1kGgNs-00027V-AM; Fri, 11 Sep 2020 10:34:24 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kGgNs-00027Q-2u for xen-devel@lists.xenproject.org; Fri, 11 Sep 2020 10:34:24 +0000 X-Inumbo-ID: dd147413-d4f6-49d3-b74a-6821e55a1981 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id dd147413-d4f6-49d3-b74a-6821e55a1981; Fri, 11 Sep 2020 10:34:23 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A3912B1EE; Fri, 11 Sep 2020 10:34:37 +0000 (UTC) To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Wei Liu , =?utf-8?q?Roger_Pau_Monn=C3=A9?= From: Jan Beulich Subject: [PATCH] x86/PV: make post-migration page state consistent Message-ID: Date: Fri, 11 Sep 2020 12:34:24 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 Content-Language: en-US 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: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" When a page table page gets de-validated, its type reference count drops to zero (and PGT_validated gets cleared), but its type remains intact. XEN_DOMCTL_getpageframeinfo3, therefore, so far reported prior usage for such pages. An intermediate write to such a page via e.g. MMU_NORMAL_PT_UPDATE, however, would transition the page's type to PGT_writable_page, thus altering what XEN_DOMCTL_getpageframeinfo3 would return. In libxc the decision which pages to normalize / localize depends solely on the type returned from the domctl. As a result without further precautions the guest won't be able to tell whether such a page has had its (apparent) PTE entries transitioned to the new MFNs. Add a check of PGT_validated, thus consistently avoiding normalization / localization in the tool stack. Alongside using XEN_DOMCTL_PFINFO_NOTAB instead of plain zero for the change at hand, also change the variable's initializer to use this constant, too. Take the opportunity and also adjust its type. Signed-off-by: Jan Beulich --- a/xen/arch/x86/domctl.c +++ b/xen/arch/x86/domctl.c @@ -215,7 +215,8 @@ long arch_do_domctl( for ( i = 0; i < num; ++i ) { - unsigned long gfn = 0, type = 0; + unsigned long gfn = 0; + unsigned int type = XEN_DOMCTL_PFINFO_NOTAB; struct page_info *page; p2m_type_t t; @@ -255,6 +256,8 @@ long arch_do_domctl( if ( page->u.inuse.type_info & PGT_pinned ) type |= XEN_DOMCTL_PFINFO_LPINTAB; + else if ( !(page->u.inuse.type_info & PGT_validated) ) + type = XEN_DOMCTL_PFINFO_NOTAB; if ( page->count_info & PGC_broken ) type = XEN_DOMCTL_PFINFO_BROKEN;